COMPOUNDS AND METHODS BASED ON /I .1.1 /PROPELLANE

This invention relates to a series of telomerε, polymers and copolymers of the monomer, [l.l.l]propellane, their manufacture, their use, and their manufacture for various applications.

These compounds have unprecedented structures. Due to the presence of bicyclo[l.l.l]pentane rings, they contain up to 14 kcal/mol strain energy per carbon atom. The rigid-rod nature of poly[1.1.1Jpropellane segments and their tendency to crystallize provide interesting properties.

[l.l.ljpropellane is a hydrocarbon compound having the following structure:

(1) This compound will be referred to at various places herein as "(l)", referring to the reference number shown below the structure. Other compounds will be similarly referenced.

Because of the highly strained configuration of this compound at the two bridgehead carbons, l.l.l]propellane has received much attention in recent years.

- 2 -

Carbon atoms normally have a tetrahedral geometry represented by the following:

\

' -

However, the two bridgehead carbons of [i.l.l]propellane have their geometry inverted such that all four bonds lie on one side of a plane. Thus, the bridgehead carbons of [l.l.l}propellane have the following geometry:

/

As a result of the invert Ped geometry, £l.l.l]propellane 10 has' very high strain energy.

The first preparation of (1) known to Applicants was described by Wiberg and Walker, 104 J. Am. Chem. Soc. at pp. 5239-5240 (1982), via a reaction of 1,3 dibromobicyclo£l.l.l]pentane with tert-butyllithiu in 15 pentane ether. Preparation by this procedure is relatively laborious and yield is low. The article also reports on various properties of (1) , and shows reactions of (1) to give 3-methylenecyclobutyl acetate and 3- methylenecyclobutene.

²⁰ A two step preparation of £l.l.l]propellane from commercially available materials was described by Se mler et al., 107 J. Am. Che . Soc. at pp. 6410-6411 (1985) . The first step involved preparation of 1,1- biε(chloromethyl)-2,2-dibromocyclopropane, and the second

25 step reacted this compound to produce a solution of (1) in pen ane/ather. The article also reports on reaction of

(1) to a thioether, preserving the bicyclo[1.1.1]pen ane ring, structure.

Free radical addition to (1) is discussed in Wiberg et al., 27 Tetrahedron Letters, No. 14 at pp. 1553-1556 (1986). It is reported that reaction of (1) with cyanogenbromide gave the 2:1 adduct as the major product, which a significant amount of 3:1 adduct. It is stated that a small amount ,of 2:1 adduct was observed in the addition of chloroform and carbon tetrachloride to (l) .

Applicants have improved the two-step procedure' or the preparation of (1) , and have also developed a new procedure, wherein e.g. a 5-20 g amount of [l.l.l]propellane at a time can be prepared conveniently. The" inventors believe that further scale-up is possible. This development makes.-this highly unusual compound available as a synthetic starting material.

Applicants' novel synthesis of [l.l.l]propellane in pentane solution (see Examples 6 and 12 below) provides the advantage of avoiding subjecting the [1.1.1]propellen to the presence of ether. Quite often, when (1) is desired to be used as a starting material to synthesize various compounds in accordance with the present invention, the presence of ether is undesired. For example, reaction of HCOOMe with (1) in the presence of ether produces diethyl ether adducts as the major products, with the desired methyl [n]staffanecarboxylate (see (2d) below) as only a minor product. In contrast, reaction of HCOOMe with [l.l.l]propellane in pentane produces only (2d) . As another example, production from (1) of a [2]staffane functionalized at both ends with iodine can not be achieved in the presence of ether. Applicants' method thus provides a [l.l.l]propellane

solution free of ether, thereby, overcoming the disadvantages experienced by the literature-synthesis.

Applicants have also effected radical addition of various reagents across he bridgehead-bridgehead bond in [1.1.ljpropellane, leading to several functionalized 1,3- diεubstituted bicyclo^l.I.ljpentanes. ^"

In view of the reactivity of [l.l.ljpropellane towards radicals, it tends to undergo radical—induced polymerization. Moreover, since an efficient route from (I) to bicγclo£1.1.13pentane-l,3-dicarboxylic acid has resulted from investigation by the inventors of radical additions to (1) as well, this long-known yet previously poorly accessible diacid is now available via ^' iϊh -present invention in large quantities for the synthesis of additional polymers by condensation.

SΌKMRRY OF TEE INVENTION

1. Molecular ^w Tinkertoy ^w Construction System

The irst broad aspect of the present invention, provides a molecular "Tinkertoy" building system, wherein various molecular civil-engineering structures can be constructed. The structures are generally constructed by attaching molecular building beams as described below to connecting units.

Thus, in accordance with one embodiment of the present invention, a molecular building beam is provided comprising a poly[1.1.1Jpropellane having the following formula:

(2)

wherein n iε the chain length, and X and Y are linking groups.

The following .preferred embodiments are of particular importance:

- n is 2, 3, 4, or 5 ,

- n is 6, 7, 8, 9, or 10 ,

- n is greater than 10 ,

- X is a group including a heteroatom, the heteroatom being bonded to a bridgehead carbon atom.

Further preferred embodiments of this type are:

- X is selected from SR, PR ₂ , NR ₂ , or BR ₂ , and SiR ₂ Cl, where R is selected from hydrogen and parent and substituted alkyls and aryls, - X is a group including a carbon atom, the carbon atom being bonded to a bridgehead carbon atoms.

Further preferred embodiments of this type are:

- X is selected from CN, NC, C(CH ₂ 0) ₃ P, C(CH ₂ CH ₂ ) ₃ N, CH(COCH ₃ ) ₂ , COOH, CSSH, and C(CH ₂ SH) ₃ , - X is selected rom parent and substituted methyls, 1 ,4-phenylenes, 1 ,3-phenylenes, trans-ethylenes , cis-ethylenes, and guinones,

- X is a poly erizable linking g oup.

A further preferrred embodiment of this type is: - X is an alkene or substituted alkene.

- a plurality of bridge carbon atoms are substituted.

A further preferred embodiment of this type is:

- a plurality of bridge carbon atoms are substituted with clorine and fluorine, - X is a nucleophilic linking group.

^F urther preferred embodiments of this type are:

- X ^" is C(CH _£ CH) N,

- ^X is selected from CH ₂ NRR ^• and H ₂ i, where _R an _d R« ^a re selected from hydrogen and parent and su _b stitute _d alkyls and aryls,

- ^X is an electrophilic linking group;

^F urt ^h er preferred embodiments of this type are:

- X is C(CH ₂ 0) ₃ SiCl,

- X is selected from S0 ₂ C1, CB Br, C _OC 1.

The term "poly[1.1.1Jpropellane" is used to mean a molecule having a plurality of bicyclo[1-1.1]pentane ring (shown in brackets above) linked together as shown in formula (2). The term includes both telomerε or oligomer (i.e. n < _, about 10) and polymers (i.e. n > about 10).

The term "linking group" means a group attached to the ^" end of a polymer or telomer which has the ability to join the polymer or telomer to which it iε attached as a ligand to connecting units, such as metal atoms.

anotechnology, i.e. -custom design and construction of mόlecular-εize mechanical structures, has been a subj ct of speculation for some time. The present invention provides or the use of telomerized and polymerized [l.l.l]propellanes as molecular building- beams, the beams preferably being end-functionalized inert, insulating, transparent and straight and having a van der Waalε radius of 2.3 A and a length increment of 3.35 A for use as construction elements. The term "[n]εtaffanes" is used herein to mean the parent hydrocarbons, where n iε the chain length. Singly functionalized telomerε (2) , may be prepared by a one-ste synthesis. Doubly end-functionalized telomerε of [l.l.ljpropellane n y also be prepared by a one-step synthesis.

Previously described molecules of this type were the formal telomers of [2.2.2]propellane (17) , known up to n - 2, and used as spacers in studies of energy and election transfer.

n (17)

Unlike the synthesis of (2) , preparation of the higher members of this series is laborious.

In a preferred embodiment of the present invention, the poly[1.1.1]propellane iε a telomer, wherein n is 2, 3, 4, or 5.

Numerous possibilities are available for the linking groups X and Y in formula "(2) . It should also be appreciated that either X or Y could by hydrogen, wherein the beam comprises a singly end-substituted poly[1.1.1]propellane. In this caεe, only the substituted end will be involved in linking with a connecting unit.

The linking groups X and Y may be selected according to the desired geometry or strength of the molecular structure to be built. It is believed that carbon-carbon linking between the linking group and staff provides a stronger bond than a heteroatom linking. Thus, X may be a group which includes a heteroatom (i.e. an atom other than carbon) , the heteroatom bing bonded to a bridgehead carbon atom of the staff. If a stronger bond is desired, X may be a group which includes a carbon atom, the carbon atom being bonded to a bridgehead carbon atom.

The beams may be attached to the connecting units at various angles in accordance with the geometry of the linking group on the beams. Thus, if a 180 ^* linking iε desired, such linking groups as -CN, -NC, C(CH ₂ 0) ₃ P, C(CH_CH_)N, CH(COCH ) , COOH, CSSH, or C(CH ₂ SH) ₃ may be used. If a stronger linear bond is desired, then 1,4— phenylene could be selected.

Conversely, angular attachments can be provided by selecting e.g. —SR, -P ^ ^-NR ' ^* ~° ^R ' ~ ^BR 2 _' • ^or "" ^S ^- ^{R C1} linking groups, where R iε preferably hydrogen or a paren or substituted alkyl or aryl. Stronger angular attachments may be obtained by using, e.g., a parent or substituted methyl, ₁ 1,3-phenylene, cis- or trans-ethylene, or guinone as a linking group.

In accordance with another embodiment, linking group X iε a polymerizable linking group, for example, an alkene or substituted alkene. Thus, X could be vinyl, -C.H _c , -CH-OC-H., —COOC.H _e , etc. • This embodiment provideε for the construction of comb-like εtructureε. That iε, the unεaturated bondε in the linking groups can be polymerized, and the poly[1.1.1] ropellane beams become "teeth" members extending from the polymer structure- formed by the linking groups.

Another embodiment of the present invention provides a molecular building beam comprising a plurality of staffs, two ends, and a linking group connected to each end. The term "staff" is used to mean a single bicyclo[l.l.l]pentane ring or a plurality of directly linked bicyclo[1.1.1]pentane rings. The staffs are connected by connecting fragments. The connecting fragments may be conductive (e.g. alkynes) , or may be

magnetic (e.g. a group containing a metal having magnetic properties, such as Fe, Co, or Ni) .

The following preferred embodiment is of particular importance: - at least one connecting fragment is magnetic,

- at least one connecting fragment is conductive.

A further preferred embodiment of this type is

- the connecting fragments are selected from parent and substituted alkynes, alkenes, phenylenes, and guinones.

Preferred is a molecular structure comprising:

a plurality of building beams, each beam comprising a poly[1.1.1]propellane having the formula:

where n iε the chain length and X and Y are linking groupε; and

a plurality of connecting unitε, each connecting unit having a plurality of accepting εiteε;

wherein at least one linking group of each beam iε connected to an accepting site and the following preferred embodiments of this molecular structure:

- T O -

- each connecting unit includes two accepting sites,

— each connecting unit includes at least three accepting sites.

A further preferred embodiment of this type is: 5 - the connecting units are metal compounds, especially transition metal compounds,

— comprising a supporting surface, wherein a plurality of the beams are anchored to the -supporting surface,

— comprising a whi -.structure, 10 - comprising a comb structure,

— comprising a scaffolding structure,

— comprising a net structure,

— X is an electrophilic linking group, and the connecting units are nucleophilic.

15 A further preferred embodiment of this type is:

— the connecting units are selected from aromatics, boranes, and metal complexes of Cj-H,.-,

— X is a nucleophilic linking group, and the connecting units are electrophilic.

20. A further pre erred embodiment -of this type is:

— the connecting units are selected from a precursor, the precursor being selected from BX,, Six., and PX_, where X is selected from Cl, Br, and I.

Preferred is a method of building molecular structures, 25 comprising the steps of: providing a plurality of molecular building beams as recited in claim 1 ; providing a plurality of connecting units, each connecting unit having a plurality of 30 accepting sites; and contacting the beams and connecting units such that at least one linking group of each beam connects to an accepting site, and the following embodiments of this method:

the molecular building beams are provided in a first solution, and the connecting units are provided in a second solution, and the contacting step comprises mixing the first and second solutions, the molecular building beams are provided in a gaseous form by subliming the molecular beams from a solid source ^• under vacuum.

Further preferred embodiments of this type are:

- the connecting units are provided on a solid surface,

- the linking groups _t . are connected to the accepting sites by epitaxial growth,

- the molecular building beams are provided in a solution, and the connecting units are provided on a solid surface, and the contacting step comprises contacting the solution and the solid surface.

In a preferred embodiment, the connecting fragments are conductive, i.e. allowing the tranεfer of electrons. Thiε embodiment provideε the advantage of facilitating the tranεfer of electronε between the terminal linking groups of the staff. It iε believed that such beams can have application to information transfer and storage technology.

Pure poly[l.l.l]propellane is an insulating chain since the bicyclo£l.l.l]ρentane rings do not allow easy electron transfer therethrough. However, by inserting conductive fragments at variouε βelected or random poεitionε between the ringε, electron tranεfer can be improved. The more the conductive frag entε are added, the more rapid the electron tranεfer through the beam will become. Thus, the degree of conductivity can be εelected by constructing beams with- εelected nu berε of conductive fragments. Suitable conductive fragments include, for example, parent and substituted alkynes, alkenes, phenylenes, and guinones.

Thus, for example, using trans-ethylene ε s a connecting fragmen , the following bean could be s nthesized:

(4)

where A iε a linking group having electron-accepting properties, and D is a linking group having electron- donating propertieε. It iε believed that electrons can be tranεf rred from D .to A. Furthermore, by converting the trans-ethylene compound to the corresponding cis-ethylene compound, the inventorε speculate that electron transfer between D and A might be further cilitated, εince D and A would then be located more proximately to each other. Thuε:

(5)

In accordance with another embodiment of the preεent invention, a molecular structure is provided, comprising a plurality of molecular building beams and a plurality of connecting units. Each beam comprises a poly[1.1.1] propellane having the formula as shown in (2) above. Each connecting unit haε a plurality of accepting εiteε. At least one linking group of each beam iε connected to an accepting site, thus joining the beams together-

^~ The term "connecting unit" iε used to mean a compound capable of joining one or more ligandε. The term "accepting site" means a site on such connecting unit which binds a ligand to the connecting unit.

In one preferred embodiment,- the connecting units are metals, such aε metal atoms or groups of atoms or metal compounds. Most preferably, the metal is a tranεition

I i I I metal, such aε, for example, Cu or Rh_

A plurality of the beams may be anchored to a supporting surface, such as a metal, cryεtalline, or glaεs surface. In thiε embodiment ^" a layer of poly[l.l.l]propellaήe of desired thickneεε may be coated on the supporting εurface.

The connecting units may be εelected to determine the geometry of the structure. If the connecting unitε εelected each have two accepting sites, then a whip structure may be created. If the connecting unitε are formed by polymerization of the linking groups themselves, a comb structure is created, wherein the molecular beams form the "teeth" of the comb. If the connecting units have three or more accepting εiteε, then star-like εtructures and net structures can be created.

In one preferred embodiment, the connecting units have at least six accepting sites. Four beams can be attached lying in a single plane and oriented 90* in relation to one another. In thiε way, a net εtructure iε created. Two beams may also be attached to each connecting unit in perpendicular orientation to the plane of the other four attached beams. By this process, a scaffolding εtructure may be constructed.

Another aspect of the present invention provides a method for building molecular structures, comprising the steps of providing a plurality of molecular building beams and connecting unitε as described, and connecting the beams with the connecting units such that at least one linking group of each beam connects to an accepting site.

In one embodiment, the molecular beams are provided in a irst εolution (e.g., a benzene solvent) , and the connecting unitε are provided in a εecond εolution. The solutions are then mixed to provide the product.

In another embodiment, the molecular building beams are provided in a gaseous form by subliming the molecular beams ^" from a solid source under vacuum. The connecting unitε may be provided on a solid surface, such as a metal or crystalline surface. The gaεeouε beams may then be directed onto the solid surface to connect the beams to the surface, e.g. by epitaxial ^" growth.

For-example, beams having a SiCl linking group may be diεεolved-in a benzene εolution. The εolution may then be contacted with a glass surface having OH contacting unitε. The SiCl and OH would react to give an SiO bond anchoring the bean to the glass surface, and HC1 would go into εolution.

Preferably, a plurality of bridge carbon atoms in the bicyclo[l.l.l]pentane rings are εubεtituted. For example, εuch aε carbons may be chlorinated or fluorinated. Chlorine εubstituents may εubεeguently be converted to other εubstituents if desired (e.g. an alkyl or aryl εubstituent) . Thiε provides the advantage of making the telomers or polymers more soluble.

2. Liquid Crystals

In accordance with another broad aspect of the present invention, a liquid crystal iε provided comprising a plurality of molecules having the formula:

(6)

Where A and B are mesogenity supporting end groups, X and Y are mesogenity supporting connecting groups, Z iε hydrogen or a εubεtituent, and n, n, and p are chain lengths such that m + n + p ^ 1.

The following preferred embodiments are of particular importance:

- A is a polar end group,

- B is a nonpolar end group,

- A is selected from parent and substituted alkyls, alkoxyls, cycloalkyls, polycycloalkyls, and aryls,

- B is selected from cyano, nitro, carboalkoxys, and acyls,

- X and Y are selected from sulfur containing goups, oxygen containing groups, a direct bond, ethane, ethylene, and acetylene,

- a plurality of bridge carbon atoms are substituted,

- a plurality of bridge carbon atoms are substituted with chlorine, fluorine, or cyano group.

The term "mesogenity supporting" in connection with A, B, X, and Y means groups which cause the molecule in which they are included to display liquid crystalline properties. Generally, the molecule should be relatively long and flexible, and the mesogenity supporting groups should be able to maintain the molecule in a generally linear and flo orientation.

A and B may be polar or nonpolar. Preferably, A and B are εelected from cyano, nitro, carboalkoxyε, acyls, and parent and substituted alkyls, alkoxylε, cycloalkylε, polycycloalkylε, and arylε. Preferably, A may be polar and B nonpolar.

Preferably, X and Y are selected from sulfur containing groups, oxygen containing groups (e.g. oxygen, ester groups, CH_0) , a direct bond, ethane, ethylene, or acetylene.

These liquid cryεtalε are believed to provide advantageε over exiεting liquid cryεtalε, displaying a lower viscosity. Thiε provideε a.quicker reεponεe time for the liquid crystal, which may be important for industrial applications. Furthermore, the pol [1.1.1]propellane unitε are DV transparent, and thus photochemically stable'. Thiε should provide a long working life for the liquid crystalε.

Preferably, A and B do not have an amine,. sulfur, or hydroxyl group, since the preεence of such a group generally makes the intermediate 1,3-disubεtituted bicyclo[1.1.1]pentane compound B(C ₅ H _β )I unεtable.

In a preferred embodiment, a plurality of bridge carbonε of the poly[1.1.1]propellane are εubstituted, for example with chlorine, fluorine, or cyano group. The subεtituted bridge carbons may be singly or doubly εubεtituted. Thiε changeε the dielectric propertieε of the molecule, giving liquid cryεtalε with negative dielectric aniεotropy.

3. Surfactants

In accordance with another embodiment of the present invention, a surfactant is provided comprising a plurality of poly[1.1.1]propellane molecules having the formula shown in (2) , wherein X iε a functional end group and Y is a surface active rou . X ma be h dro en such that the

The following preferred embodiments are of particular importance:

- X is hydrogen,

- Y is selected from the group of CO , NH P(0)(OH) S0 ₃ H, and salts of C0 ₂ H, H ₂ , P(0)(OH) ₂ , and S0 ₃ H _f

- a plurality of bridge carbon atoms are substituted, preferably with chlorine or fluorine.

Suitable surface active groups nay be εelected from the range of known surface active groupε. Preferably, Y iε selected from C0 ₂ H, NH ₂ , P(0)(OH) ₂ , S0 ₃ H, and their βalts. A plurality." of bridge carbon atomε may be εubεtituted, (e.g. chlorinated or luorinated) , which ma increaεe the εurface activity of the εurfactant.

Methods for making the molecular building beams, liquid crystalε, and εurfactantε are alεo provided by th preεent invention. Theεe methodε generally include the εteps of providing a [1.1.1]propellane and-reacting the [1.1.1]propellane with a polymerizing agent so that the [1.1.1]propellane polymerizes to a pol [1.1.1]propellane having an end group, comprising a portion of the polymerizing agent. The end group may be converted to a linking group to provide a molecular building beam. Alternatively, the end group may be converted to a mesogenity supporting group to provide a liquid crystal. In a further alternative, the end group may be converted to a εurface active group -to provide a εurfactant.

The following embodiments are preferred methods for making amolecular building beam, a liquid crystal or a surfactant: - the polymerizing agent is a radical polymerizing agen - the polymerizing agent is an anionic polymerizing age

Preferred is also a method for preparing an ether free /I .1 -lTpropellane, comprising the steps of: providing a first solution including 1,1- bis(chloromethyl)-2,2-dibromocyclopropane, a cosolvent capable of complexing lithium, and an alkane; providing an alkyllithium solution and mixing the alk llithiu solution and the first solution to produce a second solution; and separating a third solution from the second solution, the third solution including the T.1._tTpropellane and the alkane; wherein all steps are performed in an inert gas atmosphere, and the following preferred embodiments of this method:

— the cosolvent is N,N,N ,jN'— etramethylethylenedimaine

— the alkane is pentane,

— the alkyllithium is butyllithium,

— the alkyllithium solution comprises the alkyllithium dissolved in pentane,

— the inert gas is selected from argon and nitrogen,

— the alkyllithium solution comprises the alkyllithium dissolved in hexanes.

The term "polymerizing agent" iε uεed to mean a compound which induces polymerization. The term "polymerization" -is meant to include production of polymerε of telomerε. The polymerizing agent uεed above may be a radical polymerizing agent, whereby the polymerization proceedε along a radically induced mechaniεm. Alternatively, the polymerizing agent may be an anionic polymerizing agent, whereby anionic polymerization iε induced.

Another embodiment of present invention provides method for preparing an ether free [1.1.1]propellane, comprising the steps of providing a first colution including 1,1-biε(chloromethyl)-2,2-dibromocyclopropan cosolvent capable of complexing lithium, and an alkane; providing an alkyllithium solution and mixing the alkyllithium εolution and the firεt colution to produc cecond εolution; and separating the third εolution fro the second εolution, the third εolution including [1.1.1]propellane and the alkane _^ All of the ctepε ar performed in an inert gaε, atmosphere, preferably argo nitrogen.

Preferably, the coεolvent iε N,N,N ,N - tetramethylethylenediamine (TMEDA) . Another εuitable coεolvent which iε capable of complexing lithium iε 1, di(exothy)butane.

Preferably, the alkane iε pentane. The alkyllith εolution preferably compriεeε the alkyllithium dissolv in pentane. The alkyllithium iε preferably butyllithi

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 iε a diagrammatic illustration of a poly[1.1.1]propellane polymer which iε singly en functionalized with a short end group.

Figure 2 is a diagrammatic illustration of a pol [1.1.1]propellane telomer which iε singly end functionalized with a εhort end group.

Figure 3 iε a diagrammatic illuεtration of a poly[l.l.l]propellane polymer which iε doubly end functionalized with floppy end groupε.

Figure 4 iε a diagrammatic illustration of a poly[1.1.1]propellane which iε substituted at a plurality of bridge carbon atom.

Figure 5 iε a diagrammatic illuεtration of a copolymer based on [1.1.1]propellane with a plurality of bridge carbon atoms being εubεtituted.

Figure 6 iε a diagrammatic isometric view of a molecular scaffolding εtructure.

Figure 7 iε a diagrammatic top view of a molecular net εtructure.

Figure 8 iε a diagrammatic illuεtration of a molecular whip εtructure having molecular beams interconnected with εhort connecting unitε.

Figure 9 iε a diagrammatic illuεtration of a ^" molecular whip εtructure having molecular beams of varying length interconnected with εhort connecting unitε.

Figure 10 iε a diagrammatic illuεtration of a molecular whip εtructure having molecular beams interconnected with floppy connecting units.

Figure 11 iε a diagrammatic illuεtration of a molucular whip εtructure having molecular beams of varying length interconnected with floppy connecting unitε.

Figure 12 iε a diagrammatic illustration of a molecular comb εtructure.

Figure 13 iε a diagrammatic illustration of molecular ^" star εtructures.

Figure 14 iε a graph illustrating the εurface activity of a poly[l.l.l]propellane telomer having three bicyclo ring units and -CO K aε the surface active end group.

DETAILED DESCRIPTION OF TEE INVENTION

The bicyclic cage string εtructure of poly[1.1.1]propellaneε haε two unique features that made it a potential source of several new classes of unusual polymerε.

(i) Strain. The cage iε a highly εtrained εtructure (the εtrain energy of bicyclo[1.1.1]pentane iε 68 kcal/ ol) . Itε destruction iε believed to be strongly exothermic, giving it an autocatalytic character. In εpite of thiε, many bicyclo[l.l.l]pentanes are remarkably stable up to quite high temperatures (e.g. 250-300 ^# c) . By incorporating the cage as a part of a polymer backbone, the polymer iε believed to be quite stable until subjected to thermal or possibly radiation treatment at which point a deep-seated exothermic transformation occurs which leads to chain breaking. Thiε property iε potentially very uεeful in induεtrial applicationε, from the development of positive reεiεtε in the εemiconductor induεtry to itε use aε a non-polar vulcanization agent.

(ii) Rod-like shape. The 1,3-linked ring system of bicyclo[l.l.l]pentane formed upon polymerization produces a rigid rod-like εtructure characteristic of cyclolinear polymerε. Many polymers of this type have various industrically valuable properties, be it as homopolymers or as segments of copolymers. Rigid rod like materials with polar εubstituentε find uεes in the fields of piezoelectricity and liquid cryεtalε. In addition, the rigid rod-like polymers or polymer εeg entε can serve as models for many theoretical studies, prized by theoretical chemists and physicists.

Initial experiments by the inventors showed that [1.1.1]propellane can be induced to undergo radical polymerization. The polymer samples initially obtained were insoluble in all ε ^' olventε that were tried and were quite intractable. They had high melting pointε, e.g. 270-300*C, and once melted, decompoεed rapidly with gas evolution, resulting in a weight loss of 80-90* and formation of a dark carbonaceous residue. X-ray diffraction revealed- a high degree of cryεtallinity. Magic-angle spinning 1.-3C NMR analysiε showed that the bicyclo[1.1.1] entane ¹ εtructure waε preεerved in the polymer, and thuε confirmed the poly[1.1.1]propellane εtructure.

It iε believed that chain tranεfer playε an important role in the polymerization process, and many low-molecular weight telomerε or oli ^' gomers with up to five bicyclo[1.1.1]pentane units have been iεolated pure and characterized. These are thermally stable materials with quite high melting points .and characteristic spectra. The mechaniεm aεsumed to be responsible for their formation can be exemplified on the case of the addition of methyl formate:

R ^» + (1)—*- - -« ( ^β)

R- .+ + •COOMe (C)

^R *θ' ^"+HCOOMe —* ^R -~-" ^{H (E) R} "^' ⁺ CD ^• » ^{• R} - - φ< < ^F > etc.

The formation of εingly functionalized oligomerε with the variouε end groups including the following has been observed by the inventors: COOMe, CH(COOEt) ₂ , C(COOEt) ₃ , CH(CN) ₂ , C(Me) (COOEt) ₂ , C(Ph) (COOEt) ₂ , CH(COMe)COOMe, CH(CN)COOMe, P(O) (OEt) ₂ . In addition, doubly functionalized oligomerε have alεo been prepared, e.g. compounds with -SCOCH^ groups at each end, some of which are liquid cryεtalε.

X-ray εtructure determinations by the inventorε on εeveral of the oligomerε have confirmed the εtraight-rod geometry. The inter-ring C-C bond appearε to be quite εhort (e.g. 1.42-1.48 A) and intra-ring bridgehead - bridgehead separation appearε to be about 1.9 A.

The radical addition reactions on [1.1.1]propellane have produced a series of 1,3-derivatives of bicyclo[1.1.1]pentane in addition to those already described in the literature. For example, an efficient procedure for the synthesis of 1,3- bicyclo[l.l.l]pentanedicarboxylic acid, shown below as (7b) , iε provided by the present invention, so that thiε promiεing starting material iε now readily available for polycondenεation and other reactionε.

(7) (d) COMe COMe (j) COOMe COC1

(e) R I (*) SH SH

(f) R COMe

Reference will be made at variouε placeε herein to compoundε of thiε group by the reference number and lette liεted above. Thus .for example, "(7a)" refers to H(C ₅ H ₆ )H; "(7b)" refers to HOOC(C H ₆ )COOH; etc. Other groups of compounds will be similarly referenced.

The chlorination of bicyclo[1.1.1] entane (7a) is known to lead to a mixture of products in a low yield. The inventors have achieved direct chlorination of 1,3- dibromobicyclo[1.1.1]pentane (7c) to yield the tetrahalo derivative shown below aε (8a) quite cleanly.

(b) COOMe COOMe Cl Cl

(c) COOH COOH Cl Cl

(<*) C C1 COC1 Cl Cl

(8)

The inventorε have alεo chlorinated variouε other l,3-diεubεtituted[l.l.l]pentanes to yield the dichloro derivatives (8b), (8c), and (8d). Thus, an opening for the εyntheεiε of bridge-εubεtituted derivativeε of [1.1.1]propellane iε provided by the preεent invention.

Several claεεeε of polymerε baεed on [1.1.13propellane are represented schematically in Figs. 1-5.

The polymer that resulted from the inventorε initial experiments is represented _. in Fig. 1. A rough estimate of the length of the average rod 50, based on the intenεity of the end group signals in MAS C NMR εpectra, suggests that it contained about 20 bicyclo-[1.1.1]pentane units.

It is believed that more tractable polymerε are obtainable by εeveral meanε, e.g.: (i) reducing the molecular weight to produce a telomer aε εhown in Fig. 2, and/or changing the end group 56 to produce a polymer as εhown in Fig. 3 by control of the radical polymerization process; (ii) introducing εubstituents 58 into

[1.1.1.]propellane before polymerization to produce a polymer aε εhown in Fig. 4 or copolymerization to produce a polymer 60 as εhown in Fig. 5.

The intractability of the polymerε appearε to increaεe with increaεing molecular weight. Low polymerε or high oligomerε may be tractable, yet may εtill have valuable propertieε. Judicious choice of the chain transfer agent and itε concentration may serve to control molecular weight, and in addition, provide a εizeable end group (e.g. 56 in Fiq. 3) which could modify the propertieε of εuch polymerε.

Another way to avoid problems concerning the insolubility of the polymers would be to grow the polymer electrochemically on a εurface from a [1-1.1]propellane εolution.

Some of the end groups (e.g. 52 in Fig. 1) for whic telomerization has already been observed by the inventor εuch aε CH(COOEt) , C(COOEt) ₃ , COOMe, etc., lend themεelveε readily to variations. For instance, the use of long alkyl chains in a malonate could yield more soluble polymerε:

(

A feasible way to control molecular weight iε to us anionic polymerization. Experiments by the inventors indicate that εtrong nucleophiles (εuch aε n-BuLi) can polymerize [1.1.1]propellane under certain conditions. iε believed that εubstituted derivatives of [1.1.1]propellane can be used to produce homopolymerε or copolymerε that exhibit a lower degree of cryεtallinity, thus enhancing the solubility of the polymer, and possib introducing other interesting properties.

It is believed that εubstituted propellanes will be accessible from the diacid (5b) , a starting material that can be synthesized via the present invention to uεe on a large εcale. It iε believed that tractable aterialε will result when [1.1.13propellane is copoly erized with other compounds, e.g. εtyrene, acrylate, and methacrylate onomerε:

It iε believed that alternating type copolymerε with [1.1.1]propellane are alεo achievable. For example, copolymerization -with aleic anyhdride (which doeε not . homopolymerize) should produce the following:

(ID

Such a polymer (11) iε anticipated to be εoluble due to the great increase in polar groupε, and to be reactive due to the anhydride εtructure.

Another anticipated way of combining [1.1.1.]propellane with other units in the baclcbone iε the us of oligomer building blocks in polycondensation. It iε expected that access to bifunctional low molecular weight oligomerε (e.g. 5-20 cages per chain) will be ^' gained via chain transfer techniques. The tranεfer agent and/or initiator provide end groups that it iε anticipated can be modified to produce macromerε. For example:

COOCH ₃ — > Eocs ₂ .φ+ - E ₂ OR (N)

(12 )"

Subsequent polycondensation may then be carried out, for example to produce polyurethaneε:

Once again, there are numerous poεεibilitieε for the generation of 'hard' and 'εoft' segmented polymer chains

It iε alεo believed that the diacid (5b) can be uεe to synthesize polyesters, polya ides, etc:

Variouε other derivativeε of the type (7) may be used, εuch aε glycolε, άiamines, etc.:

o o n (7) + n H ₂ —A— H ₂ > 4-NH—Λ—NH-C—A—c - (Q

Once again, εuch material should be soluble.

Another interesting aspect of the present invention iε provided by anionic polymerization. Sequential addition of another monomer, εuch as a conjugated diene, to a living polymer εhould reεult in AB block copolymerε Should anionic polymerization be feaεible, the uεe of difunctional initiatorε could yield ABA block copolymers with either rigid central or end blocks. Such εtructure are of well known industrial importance.

Another method of preparing poly[l.l.l]propellanes provided by the present invention includes growing the telomer or polymer on a εurface electrochemically. In thiε embodiment, an electrode iε immersed in a εolution

containing [1.1.1]propellane, whereby the bicyclo[1.1.1]pentane rings link to the εurface and to other linked rings to grow poly[l.l.l)propellαnes. Preferably, the εolution iε a hydrocarbon solution to avoid undeεired reactionε of the radicals with the solvent. The length of the chainε can be controlled by reaction conditionε. Thiε embodiment avoidε the problem of inεolubility of poly[1.1.1]propellaneε, since the compoundε are grown directly on a solid εurface, and thus need not be εoluble.

Other Potential;Pεeε. (i) Resists. One anticipated utility of the [1.1.1]propellane based polymerε iε aε positive reεiεtε. It iε believed that the high energy content of the bicycϊo[1.1.1]pentane ringε, combined with the.instability of cations derived from the bicyclic ring εyεtem, make the polymerε εuitable for e-beam and X-ray resists, photo resists, and thermal resiεtε.

Since destruction of the bicyclo [1.1.1 pentane cage by radiation is expected to cause chain scission, it should be necesεary to include only a ew percent of cage structures in another polymer εtructure to produce an effective resist. Since low percentage of propellane units in the backbone of the parent polymers iε anticipated to affect the solubility characteristicε of the latter only minimally, the coating of the resist should be feasible.

(ii) Optical storage media. Since poly[1.1.13propellane demonstrates a dramatic weight loss at about 300*C, materials of this kind (with suitable doping) are anticipated to be useful permanent optical storage media for ablation from a thin polymer layer.

Unlike the presently used thin layers of tellurium alloys, the ^, polymerε provided by the preεent invention are highly stable in air. The εuddenneεε with which the decomposition εets in provides the advantages that the polymer layer will be stable to bake-out up to around

250*C and to low-level intensities of reading light, yet ablate readily just above 300*C, leaving a little, very dark residue with essentially no reflectivity. Thus, for example, a layer of poly[1.1.13 ropellane may be depoεited on an optical recording εurface, and high-temperature beams may be applied at selected locations to create craters which may serve aε optical recording/storage εites.

It iε advantageous to uεe a soluble polymer for thiε purpoεe, both for the .ease of spin-coating and for the incorporation of a dye, which will be required to aεεure high absorbance in the near IR region where diode laεerε typically operate. Such dyeε aε l,l,5,5-tetrakiε(p- dimethylaminophenyl)-2,4-pentadien-l-ol perchlorate (lambda at 830 nm, 630nm) , and l,5-biε-(p- dimethylaminophenyl)-1,5-diphenyl-2,4-pentadien-l-ol perchlorate (lambdam_ax„ at 823 nm, 525 nm) , can be used if they are accepted in εufficient amountε into the polymer. In view of their high solubility in chlorinated polymerε, uεe of chloro εubεtituted polymerε are preferred.

(iii) Piezoelectrics. Crystalline polymerε, εuch as polyvinylidene fluoride, which contain strongly polar groups which may be oriented to form electretε by thermal and electrical treatment exhibit piezoelectric properties. I has recently been demonstrated that polymers which have a monocyclic repeat unit and contain a polar- group posses piezoelectric properties aε well. A poly[1.1.13propell ne containing a polar group, εuch as a halo or cyano subεtituent, iε thuε anticipated to be an ideal candidate for a piezolectric polymer.

(iv) Electron and Energy Tranεfer Rates. Polymerε baεed on [1.1.1]propellane having electron donor/acceptor and functional groups represent an interesting series of

βpacers for measuring the rates of electron or energy tranεfer aε a function of the number of intervening bonds and of interposed εuperexchangerε [e.g., C^C) , aromaticε, lateral εubstituentε]. For example, the following poly[1.1.1]propellane may be uεed:

CH ₂ A ' (

Electron tranεlόcation rateε in the radical anions may be meaεured e.g., by pulεed beam radiolyεiε. Double εtrands, in which an additional chain which iε not necessarily rigid in itself [e.g., oligosilane or

—(O-metal) —] iε strung along a beam, can be uεed to meaεure the transfer rate incre entε due to more highly conducting chainε of bonds.

(v) High Energy Materials. Due to the high strain energy of the bicyclo ring tinits, it iε believed that εuch telomerε and polymerε baεed on [1.1.1]propellane have application as high energy materialε.

1. Molecular "Tinkertoy" Construction System

One embodiment of the present invention provides for the use of telomerε and polymers based on

[l.i.l]propellane in a εyεtem for building molecular εtructureε. Building blockε are provided for a molecular-εize mechanical construction set (e.g. rigid molecular building beams having terminal linking connectors for connecting the beams, etc.) , permitting the aεεembly of novel classes of materialε. Such materialε may be attached to well—defined surfaces, preferably metal surfaces.

In a preferred embodiment of the present invention, a scaffolding type molecular εtructure 70 aε εhown in Fig. 6 iε provided. Inεertion of εtraight beamε 72 between the lattice pointε of the rigid beam connecting units or connectors 74 produces an "exploded" solid 70 with potentially very large regular voidε 76 accessible to counterions, small εolvent moleculeε, etc. The electric and magnetic propertieε of the lattice pointε and of the rigid beam connectors 74 can be controlled by their chemical nature and length. The structures may βelf- aεεe ble by epitaxial growth on a regular εurface, or aε a reεult of a suitable choice of the εize of counterions located in the voids 76. They may be amenable to Merrifield-type synthesis in thin layers, with alternating layers of one and another metal, etc.

In another embodiment, a two-dimensional net or sieve 80 aε εhown in Fig. 7 with holeε 82 of controlled size iε provided.

The molecular structures provided by the invention are capable of nearly infinite variation by attachment of tethered functional groups onto the εtraight beams, providing an opportunity for blocking the voids by cross- linking, controlled reversibly (e._g., 2-SH -S-S-) or irreversibly (e.g., photochemical chain εciεsion) . This offerε dynamic control over the εize of molecules capable of diffusing through the "exploded" solid, say to an electrode, to a catalyεt, etc.

In yet another preferred embodiment, linear polymerε are provided. Referring to Figs. 8-11, theεe polymerε reεult from the insertion of εtraight rigid beams between lattice pointε on a line. For example, molecular cables or whipε compoεed of εeveral interconnected βtrandε may be built. Some strands can be proton-conducting (e.g. via series of hydroxy or a ino εubstituents) or electron- or

ion-conducting (e.g. via chain of metal or metal oxide containing εubεtituentε) . Inεertion of these εtructures across membranes or other layers can yields ore complex assemblies. Variouε forms of copolymerization may be used to incorporate oligomeric building beams into the backbone, either in a regular fashion (see Figs. 8 and 9) , or randomly (see Figε. ^; 10 and 11) , separated either by εhort εegmentε of the backbone (εee Figs. 8 and 10) or by long εegmentε (εee Figs. 10 and 11) .

The bridge carbons of the bicyclo[l.1.13pentane units of a poly[l.1.13propellane telomer or polymer can be functionalized to construct a molecular ladder εtructure of two periodically connected molecular wireε. For example, such a ladder having the partial formula (13) can be constructed:

I 1 I 1 O O O O

Cu Cu Cu (13)

Where ^ iε an end group capable of one electron oxidation, and R_ iε an end group capable of one electron reduction.

in thiε εtructure, the "wire" comprised of the bicyclo ring unitε actε an an inεulator while the "wire" compriεed of the copper atomε actε aε a conductor for electron transfer between the terminal εubstituentε R ₁ and

e low-molecular weight oligomerε of

[1.1.1 propellane functionalized on one end can be used to produce comb-like polymerε with rigid-rod "teeth", as εhown in Fig. 12. Two modes of attachment of the beams as "teeth" are anticipated.

In the first, the attachment iε through carbon atoms and requires the attachment of an olefinic residue to the oligomer. For example:

(14) (

The starting material (R «= H) can be obtained from the already available acid. Other choices of R may yield comb-like polymerε capable of further tranεformation and croεε-linking (e.g., for R - COOMe, by condenεation with glycol or a diamine) .

The εecond mode of attachment iε through a heteroatom. The inventorε believe that the oligomeric unitε may be attached to a preformed functionalized polymer chain, εuch aε poly(vinyl alcohol) , to wit:

Alternatively, it iε believed that an unsaturated monome εuch as a methacrylate, attached at one end of the oligomer may be polymerized, e. g. :

(15)

(15) -->-R -0-CO-CHe«CH ₂ (K) n

Star-like polymeric εtructureε aε provided by another embodiment and εhown in Fig. 13 are. of considerable theoretical interest. Access to star-like polymerε iε anticipated by the use of anionic polymerization of [1.1.13propellane and polychlorinated.εilanes, diεilanes or triεilanes as terminating agents.

Another embodiment provides a molecular windmill, wherein controlled motion is offered by excitation of vibrations and rotations with radiation, ordinary photochemical events εuch as cis-trans isomerization of double bonds, temporary charge separation in donor- acceptor structures, etc.

Molecular windmills in accordance with the present invention comprise a molecular building beam attached at

one.end to a εurface (e.g. metal) and at the other end to a metal connecting unit having a plurality of accepting sites. A plurality of flat ligand "wings" are attached to the metal connecting unit, the wings being attached angularly in relation to each other, preferably perpendicularly.

For example, the following molecular windmill can be constructed:

where L iε a connecting group or ligand.

The wingε attached to the Rh are generally flat or nearly flat ligands. For example, they could be the following:

The molecular wings may be artificially rotated by, e.g., a helium stream. It iε believed that if the wings are oppoεitely charged, then their rotation will produce a microwav .

Preferably, the molecular building beam forming the baεe of the windmill iε attached perpendicularly to the εupport surface for εtructural εtability. Alternatively, for even greater εtructural stability, three or more beam could be attached to the surface as "legs" of the windmill. In thiε embodiment, each beam iε attached at one end to the εolid εurface, and at the other end to the came metal connecting unit either directly or via another connecting group.

Applicantε believe that molecular εtructureε aε provided by the preεent invention are applicable to many uεes. In addition to the uεes mentioned earlier. Applicants feel that the "Tinkertoy" εtructureε may be uεeful in the field of microelectronicε ^' . For example, molecular sized electric motorε and εensors may be constructed. Structures having voids between the beams may be used as inclusion complexes to house ionε within the lattice, or as molecule εieveε to purify gaεeε. 'Such εtructures could alεo be uεed aε molecular εieveε in εolution to prevent undesired paεεage of certain compounds or complexes therethrough. Thus, for example, the sieve could function as a barrier to protect a catalyst.

Straight, cheap, and readily accessible rigid molecular building beams are preferably used in the present system. They are preferably stable in air and otherwise chemically resistant well above room temperature, available in a variety of finely graded lengths, transparent down to the vacuum UV, electrically insulating, and yet available not only in a form functionalized in a pre-εelected manner at both ends, but alεo in formε containing one, εeveral, or many additional pre-selected εubstituentε at εpecified pointε along their length.

Such molecular building beams are provided by the present invention in the form of oligonerε of [l.l.i] propellane. For example, εuch oligomerε (2) may have the following εtructure:

(2)

X Y X Y

(a) εcoMe ₃ SCOMe ₃ (i) H C(Ph) (CO0Et)

(b) H COO (j) H CH(COMe)COOM

(c) COOR COOR (k) H CH(CN)COOMe

(d) H COOMe (1) H P(0)(OEt) ₂

(e) H COOH ( ) COOH COOH

(*) H CH(COOEt) ₂ (o) Br Br

(g) H C(COOEt) ₃ (P) PhCH ₂ Br

(fa) H CH(CN) ₂ ( ) SBU SBu

(r) SAC SAC

0 SH SH

Large amountε of telomerε (2) are formed by radical additionε to [1.1.13propellane and can be εeparated, and can be functionalized at one or both ends. For example, telomer (2a) where n=4 can be formed. Monoesterε (2b) c be chlorocarbonylated on the free end to yield the dieεterε (2c).

The telomerε of [1.1.13propellane fulfill the requirements for the εtraight beams of the molecular "Tinkertoy" construction set in accordance with the present invention. In εpite of their high εtrain energy (on the order of 68 kcal/mol per bicyclo[1.1.1]pentane unit) , they are εtable up to 250-300*C. X-ray analyεis indicates that the increment length iε approximately 3.35A.

In a preferred embodiment, doubly functionalized molecular building beams are provided having metal ligating groups on both ends, ready for the use of dative bondε to tranεition metal atoms aε molecular connecting 5 unitε. Attachment of beamε in a linear orientation with .reεpect to the metal ligand iε provided when X and/or Y ■* CN, NC, C(CH ₂ 0) ₃ P, C(CH ₂ CH ₂ )N, CH(COCH ₃ ) ₂ , COOH, CSSH, C(CH_SH)_, etc.? attachment in an angular orientation iε provided when X and/or Y ■« SR, P ,, NR_, etc.

10 In an alternative embodiment, covalent connections are-constructed. Thiε may be accomplished by providing at ^' least one electrophilic linking group (such aε C(CH ₂ 0) ₃ SiCl for linear and S0 ₂ C1, CH.,Br, C0C1, etc., for angular attachment) on a plurality of beams. Such beams

■J5 may be combined with a plurality of beams having at least one nucleophilic end group (εuch aε a ino). Nucleophilic linking groupε may be used for linear [e.g. C(CH_CH) ₃ N] or angular (e.g. CH ₂ H ₂ , CH ₂ Li) attachment to electrophilic linking groups. - Alternatively, the beams with 0 electrophilic linking groups may be combined with nucleophilic connectors, εuch aε aromaticε, metal

2— complexes of C_H _S -, boranes εuch as B ₁ ^H 12 ' ^etc * ^A further alternative provides for-the-beams having nucleophilic linking groups being attached to 5 electrophilic connecting units, such as BC1 ₃ , SiCl., PC1 ₃ , etc.

In still another embodiment, molecular beams are provided having charged end groups, such as S0 ₃ - or NR ₃ +. Thiε provideε the advantage of an essentially non- 0 directional mode of attachment by electrostatic interaction.

By way of example, polyεilaneε may be built using th molecular Tinkertoy εyεtem of the present invention. Polyεilanes are believed to be uεeful aε photoresists. Oligoεilane chainε may be racked onto the molecular beams of the present invention to fix the desired conformation. For example, a double ercaptan molecular beam can be converted via the following:

HS

(W)

In a preferred embodiment, a first layer of molecula beams are anchored to a flat εurface in an epitaxial faεhion. Metal atomε from various sources may be uεed aε anchor sites, εuch aε eta.l atomε of a monolayer of a metallophthalocyanine, of under-potential-depoεited metal atomε on an electrode, iεlandε of vapor-depo it d metal atom clusters, and other regular surface patterns.

EXAMPLES

The following examples are designed to illustrate certain aspects of the present invention. However, they should not be construed as limiting the claims thereof.

Example 1 — [1.1.1]propellane can be prepared from methallyl dichloride. The inventorε have detected the formation of numerous telomers under radical addition conditionε, e.g. (2d)-(21), wherein n - 1 - 4 or 5 and isolated many of them in pure state. Their relative amountε have depended on the choice of reactant concentrations. Chlorocarbonylation of (2d), n « ₂ , ₃ has yielded derivatives of (2m) . Some of the attempte _d

telomerization reactions did not proceed βmoothly. E.g., tthhee rreeaaccttiioonn ooff PPhhCCHH ₂₂ BBrr wwiitthh ((11)) yyiieelded some (2o,n«=2) , and bibenzyl in addition to (2p,n=l)

Efficient preparation of (2d) seems to require ether-free solutions of (1) , obtained in a 15-30% yield based on methallyl dichloride by substituting TMEDA for ether in the Szeimies synthesis. In a typical procedure, a 1.4 M εolution of (1) in pentane (65 ml) reacted with methyl formate (800fm ) upon irradiation in the preεence of benzoyl peroxide ?(0.4 g) . The individual telomerε (2d) were εeparated by cryεtallization of the acidε and potassium salts and by sublimation. Based on methallyl dichloride, the overall three-step yields of purified materialε were about 3-6% for n -= 1,2, about 2—4* for n • 3,4, and about 1-2% for n « 5, with about 3* of (1) accounted for aε higher molecular weight material. It iε poεεible t ^' o find reaction conditions under which only the monomer (n ■= 1) iε formed. At low concentrations of methyl formate and also under anionic polymerization conditions (n-butyllithium, 2-25*) , practically only a

(2d) polymer was obtained (unoptimized yield, about 50%) .

Example 2 — The telomers (2) have very high melting points and thermal stability (up to about 300 ^β C) , considering their high energy content (the εtrain energy of bicyclo[l.l.l]peritane iε about 68 kcal/mol) . Differential εcanning calorimetry on a sealed sample of (2d,n«4) εhowed a decomposition exother at about 320*C (145.7 kcal/mol). The (2d) polymer decomposed violently at 290'C with approximately 80% weight loεε. In keeping with the _, high melting pointε, the solubility of the higher telomerε was poor and no solvent for the (2d) polymer was found. Its X-ray diffraction pattern εhowed a high degree of cryεtallinity. Itε εolubility waε increaεed dramatically upon extenεive chlorination. Thuε, it iε believed that εubεtitution will improve the εolubility of all the telomer .

Example 3 - X-ray εtructure analyεiε on (2d,n«2) , and (2o,n«=2) , yielded an inter-ring C-C bond length of about- 1.48 A, and a bridghead — bridgehead εeparation of abou 1.9 A. In (2a,n«=3), the inter-ring diεtances were even shorter, about 1.47 A. Neighboring staffs appeared parallel and meshed in the crystal, with axes only about 4.6 A apart. Thiε very efficient packing iε presumably reεponεible for the high melting pointε.

Example 4 - The εaltε of the acids (2b) were εurface active. In the concentration range of 1.4 x 10 to 3 x

10 —4 M' , the εurface tenεion of an aqueouε εolution of the potaεεium.εalt of (2b,n«=3) , followed gamma - -17.7 log c

2 0.2 dyn/cm (107 A of εurface area per molecule). Langmuir-Blodgett films were prepared uεing the Cd 2+εalt of (2b,n=3) (45 A ² /molecule) .

Example 5 - The NMR εpectra of the "εtaffε" εhowed each equivalent claεε of ^ and C nuclei up to n » 5. Large bridgehead-bridgehead coupling conεtantε were attributed to transannular orbital interactions. E.g., in (21,n=2) , ⁷ J[ ²¹ P ¹ H] was 1.7 Hz. The CP-MAS ¹³ C NMR spectrum of the (14d) polymer consisted of a peak at , 50.8 (bridge), a sharp peak at 40.3 (bridgehead) and weak end-group εignalε at 169.7 (carbonyl) and ≤7.8 (methine) .

Example 6 — Preparation of Propellane Solutions

Synthesiε of 1,1-biε(chloromethyl)-2,2-dibromocyclo- prσpane (18) on a 2 mole scale produced a consiεtent 29- 31% yield in production of rigorouεly pure material. Preparation of [1.1.1]propellane .from the tβtrahalide precursor (18) was best achieved using MeLi in diethyl ether. ("Procedure A") . Ether free propellane iε

available from an alternate procedure using BuLi and TKED with (18). ("Procedure B") .

(18)

After distillation or the crude εolution (40-80% yield), 1.5 M [1.1.1]propellane in pentane, free of halides, was produced in 30-60% from (18) . The yield was probably varied by anionic polymerization of propellane.

Both εolutionε were εtable εhowing only εmall change in concentration over long periods under oxygen-free conditions at a freezer temperatxire of about —15*C.

Example 7 - Preparation of Sulfur Compounds

Photolysiε of one equivalent of εymmetrical alkyl or acyl diεulfides in an ethereal εolution of propellane gav at least four oligomerε. As expected, relative yields of oligomers were strongly dependent upon concentration of starting.material. Steric hinderance of the RS radical a from t-butyl diεulfide, or pivaloyldiεulfide, completely prevented formation of any diεulfide derived product. In contrastj aryl diεulfides, for instance the parent diphenyldiεulfide (and dipenyldiεelenide) , produced largely the firεt adduct.

Aceticthiol acid (CH COSH) addε to (1) giving only a firεt adduct, i.e. acetylthiobicyclo[1.1.1]pentane. Thiε compound iε a convenient precurεor for εynthesizing the corresponding mercaptan and disulfide.

Example 8 - Halides

Bromine and iodine add to propellane, abeit in small yield, due to rapid decomposition. Even iεolated product had.to be rigorously purified and stored in the dark at low temperature. The more useful adductε, however, were derived from additions of organic halides. Alkyl iodides aε in the case of the iodine adduct, provided unstable products containing no oligomerε. Generally yieldε were moderate (with the low output exception of Mel) . Unεubεtituted or withdrawer εubεtituted aryl iodideε were coaxed to produce a diεubstituted bicyclopentane with Procedure B propellane. However, accompanying side reactions εuch aε hydrogen abstractions made the synthese less than optimal, and no products were observed from donor εubεtituted arylε εuch as iodoaniεole. Behavior of homologous alkylε εeemed to parallel εtability of the radicalε formed from bond homolysiε.

An unuεual iodide tranεfer reaction was observed in the photolysis of l,3-diiodobicyclo[1.1.1]pentane in the presence of propellane in pentane. 3,3'-bisiodo[2]εtaff- ane, was the εole product, formed largely aε a precipi¬ tate, which waε not induced to form higher oligσmerε.

Alkyl bromideε were largely inert to photochemically initiated addition to propellane, except when a particu- larly ctable radical waε formed, aε in the caεe of t-BuBr and benzylbromide, or alpha-carbonyl activated bromide εuch aε•methylbromoacetate or — alonate. Aε with alkyl iodideε, no oligomerε were formed. Bromide transfer reactionε with l,3-dibromobicyclo[1.1.1]pentane in the presence of [1.1.1]propellane were not achievable.

However, reaction with benzylbromide gave 3,3'-dibromo- [2]εtaffane aε a side product.

Example 9 — Physical Properties of Oligomers

NMR shifts varied in a predictable pattern aε the bicyclopentyl repeating unitε were added incrementally. Typically, proton or carbon reεonanceε shifted upfield th further the atoms were ¹ located from the ends of the molocule.

X-ray structures eεtabliεhed in the monoεubεtituted caεe that interring distances were considerably shorter than normal C-C bonds. 3,3"-biεacetylthio[3]εtaffane diεplayed a tight interlocking packing arrangement with a iπterplane distance of about 4.6A.

Examples 10-25

Boiling points in these examples were uncorrected. Melting pointε were determined by Boetius PHMK05 apparatu with microscope attachment at a warm up rate of ^β C/min. or in sealed capillary and were uncorrected. NMR spectra were run on a Nicolet NT-360 in CDC13 as a solvent unless specified otherwise. Infrared spectra we ^' re recorded on a Nicolet 60SXR FTIR.

1.4M solution of ethyllithium in ether (halide free) , bromoform of 96% purity and 3-chloro-2- chloromethyl-1-propene of 94% purity were purchaεed from Aldrich Chemical Co. and uεed with no further purification. All operationε and reactionε involving [l.l.l]propellane were performed under an atmoεphere of dry argon. Photochemical reactionε were carried out at ice bath temperature, using a 450W medium pressure Hanovia mercury lamp; the solution was contained either in a round bottom pyrex flaεk or in a pyrex immerεion photolyεiε apparatuε. A typical run εcale waε 0.1 mole of 1,1- biε(chloromethyl)-2,2-dibromocyclopropane (unless specified otherwise) and the etheral solution of the

propellane was used for reactions with no further separation or puridication soon after generation. Preparative βcale gas chro atography was carried out on 10% SE-30, 6ft column. X-ray εtructureε were determined on a Suntex Diffractometer equipped with a graphite monochromator.

Example 10 — 1,1-bis(chloromethyl)-2 ,2-dibronocyclopropan

1000 ml of 50% εodium hydroxide waε added in 10-15 in. to a vigorouεly stirred mixture of 370 ml (4.24 mol of bromoform, 250 g (2.0 mol) of 3-chloro-2-chloromethyl- 1-propane, 10 g of benzyltrieth'ylammonium chloride, 8 ml of ethanol and 200 ml of methylene chloride. The temperature during the addition as well aε later was maintained between 25-35'C, controlled by lowering the reaction flask in an ice bath. After overnight stirring, 500 ml of methylene chloride was added and the thick blac mixture was allowed to separate into layers. The top aqueouε layer was removed and the bottom layer was gently washed with 500 ml portions of water. 500 ml of water wa - then added, well shaken, and left for phase εeparation.

The clear, dark-brown organic phase was separated and the residual emulsion waε treated with solid εodium chloride and filtered through Celite which aided separation. All aqueouε layerε were washed with methylene chloride and th organic extractε were combined, dried over magnesium εulfate, and filtered through Celite. Concentration and vacuum distillation gave 350-380 g of a mixture of starting material and black-brown residue which waε diεtilled on a Kugel-Rohr giving 315-350 g of εemicry- εtalline fraction (65'C/0.45 mm Hg up to 115'C/ 0.9 mm Hg containing the product. Crystallization from 400 ml of pentane from a dry ice-acetone bath gave 205-215 g of white wet cryεtalε ( p 38-41'C) . The crude product was diεεolved in 400 ml of pentane, 7.5 g of silica gel was added, filtered and ^' low temperature recrystallized again,

giving 171-182 g of product which melted at 44-46 ^* C. One more cryεtallization (400 ml of pentane) gave 164-175 g (29-31% yield accounting 94% purity of εtarting olefin) o pure compound: mp. 47"C (lit. 45-6 ^* C) ; TI NMR 1.82 (ε, 5 2H), 3.94 (d, J«11.9 Hz, 2H) , 3.99 (d, J-11.9 Hz, 2H) ; ¹³ NMR 32.07, 34.07, 35.35, 47.67.

Example 11 — [1.1.1]Propellane in Diethylether (Procedure

29.7 g (0.1 mole) of l,l-biε(chloromethyl)-2,2- dibromocyclopropane ^" and 30 ml of pentane were placed unde o argon in a 500 ml three neck flaεk equipped with mechanical εtirrer, εeptum, and εide arm connected to col trap. 170 ml (0.24 mole) of methyllithium in ether waε added through εeptum with vigorouε εtirring, in a period of 10 min. at —78*C. When the addition was complete, the dry ice-acetone bath waε replaced by an ice bath. The yellowiεh reaction mixture waε εtirred for 1 hr and then all volatiles were vacuum transferred (50 mm Hg) to a dry ice-acetone trap. When almost dry εaltε appeared in the flaεk, the vacuum waε diεconnected and the apparatuε was opened to dry argon atmosphere. 210 ml of colorless clear solution was obtained. ^ NMR (C _fi D ₆ ) εhowed εignalε belonging to: diethylether 1.03 (t, J-7.1HZ, 6H) , 3.25(q, J-7.1Hz, 4H) ; methylbromide 2.27 (ε); [1.1.1]propellane 1.76 (ε) ; pentane 0.79 (t, J-6Hz,6H), 1.19 (a, 6H) in the following proportionε 100:5.5:3. -:6.25. Concentration of tthhee pprrooppeellllane calculated baεed on H NMR εpectrum waε 3% (by weight)

Example 12 — [l.l.l]propellane in pentane εolution (Procedure B)

29.7 g (0.1 mol) of l,l-biε(chloromethyl)-2,2- dibromocyclopropane, .20 ml of N,N,N',N'-tetramethylethy lenediamine (TMEDA) and 50 ml of pentane were placed un argon in a 500 ml 4 neck flask equipped with mechanical εtirrer, εeptum, low temperature thermometer, and εide connector to cold trap. The εolution waε cooled to -50* and 22 ml of 10.0 M'^BuLi were added via cannulation keeping the temperature below -30*C. When addition was complete, the mixture was stirred for 0.5 hours at -20* and H ₂ 0 added until further addition did not affect the temperature (2 ml) . Vacuum tranεfer at room temperatur gave a clear εolution leaving a viscous brown liquid: crude propellane εolution (42-75% yield by NMR compariε to theoretical amount of benzene) waε cannulated by arg preεεure from the -78'C collection flaεk to a diεtillat apparatus featuring a 10 cm Vigreaux column. Keeping t pot temperature below 90*C, a εolution of propellane (3 yield) waε obtained containing only hydrocarbonε.

Example 13 - 1,3-Dibromobicyclof1.1.1] entane.

12.8 g (0.08 mol) of bromine, freεhly diεtilled fr ^P ₂ ° ₅ ' ^was added dropwiεe to a εtirred 0.1 mole portion propellane εolution prepared by Procedure A. The resulting mixture was evaporated and an oily yellow residue waε cryεtallized from pentane at low temperatur (-78 ^β C) giving 2.9 g (16% baεed on bromine) of white cryεtalε (mp 110-115*C) . Recryεtallization gave pure l,3-dibromobiσyclo[1.1.1]pentane: mp. 122 ^* C (εealed capillary) (lit. mp. 118*C); ^ NMR 2.57 (ε) ; ¹³ C NMR 30.46, 64.72.

Example 14 - l _r 3-Dliodobicyclo[1.1.1]pentane

11. g (0.045 mole) of εublimed iodine diεsolved in 100 ml of dry ether were added dropwiεe to a magneticall εtirred 0.1 mole εolution prepared by Procedure A. The 5 reεulting εolution was evaporated and the yellow to brownish crystalline mass diεsolved in chloroform and passed through a εhort εilica gel column. To the εlight pink eluent, 10 ml of heptane waε added and the εolution waε evaporated to dryneεε giving 5.0 g of white cryεtalε 0 of the diiodide: mp ^r . ^' 153*C dec. (εealed tube); Tϊ NMR

2.67 (ε); ¹³ C NMR -1.80, 68.25; EIMS, m/z (relative intensity) 320(5), 193(40), 128(35), 127(43), 66(100),

65(70); HRMS, a/z (calcd for C5H6I2: 319.85590) 319.8563

Anal, calcd for C5H6I2: C, 18.77; H, 1.89; I, 79.34. 5 Found: C, 18.84; H, ^" 1.90; I, 79.24.

Example 15 — l-Bromo-3-t-Butylbicyclo[1.1.1]pentane

A magnetically εtirred εolution of the propellane (prepared on a 0.05 mole εcale via Procedure A), 35 ml o tert-butyl bromide and 0.4 g of benzoyl peroxide waε ° irridiated in a round bottom flaεk for 10 hr. Evaporati of the solvent and the exceεε of t-butyl bromide followe by short path diεtillation gave a βemicryεtalline fraction. Low temperature cryεtallization from pentane ^" gave a white product: mp. 80.5-81.0*C; H NMR 0.84 (ε, 9H), 2.03 (s, 6H) ; ¹³ C NMR 26.45, 31.02, 37.62, 49.65, 55.48; EIMS, m/z (relative intensity) 205(2), 123(12), 107(28), 91(62); HEMS, m/z (calcd. for C9H15: 123.11738) 123.11775; Anal, calcd for C9H15Br: C, 53.21; H, 7.44; B 39.34. Found: C, 53.15; H, 7.44; Br, 39.25.

Example 16 - l-Benzyl-3-bromobicyclo[l.l.l]pentane and 3,3'-dibromor2]staffane.

A mixture of the propellane εolution (prepared on a 0.05 mol scale via procedure A), 7 ml of benzyl bromide and 0.3 g ofbenzoyl peroxide waε irradiated in a round bottom flaεk for 15 hr ^' . Solventε were evaporated, exces of the benzyl bromide waε distilled of under vacuum (40- 43*C /0.9 mm Hg) and the residue was εhort path diεtille giving a βemicryεtalline fraction (80-10*C/0.6 mm Hg) . Cryεtallization from pentane (or heptane) gave 3,3'- dibromo[2]εtaffane, which after sublimation (90 ^# C/1.0 mm Hg) gave an analytical εample: mp. 175 'C (dec. εealed capilliary to a brown liquid at 203 ^# C; ^ NMR 2.11 (έ) ; ¹³ C NMR 36.30, 40.18, 57.90; Anal. Calcd for C10H12Br2: C,41.13; H, 4.13; Br, 54.73; Found: C, 41.17; H, 4.18; B 54.64. The filtrate waε cooled in dry ice-acetone bath and the reεulting white cryεtalε were filtered off. Recryεtallization followed by vacuum εublimation gave a εample having the following: Tϊ NMR 2.06 (ε, 6H) , 2.83 ( 2H), 7.04-7.08 ( , 2H), 7.18-7.31 (m, 3H) ; ¹³ C NMR 41.55 58.45, 126.29, 128.38, 128.70, 138.33; EIMS, m/z (relati intensity) 157(62), 129(100), 128(36), 117(59), 116(55), 115(94), 91(93), 65(40), 39(35); HEMS, m/z (calc for C12H13: 157.10173) 157.10218.

Example 17 - l-Butyl-3-iodobicyclo[1.1.1]pentane.

A solution of the propellane (prepared on a 0.05 mo scale via procedure A) and 7 ml (b.053 mol) of 1- iodobutane waε irradiated in a round bottom flaεk for 5 (until no more progress waε monitored by GC) . ^" Solventε were evaporated and diεtillation of the yellowish residu gave 4.2 g (34%) colorleεs liquid (bp. 54-55"C/0.8 mm Hg which gradually turned brown upon standing: H NMR 0.87

(t, J-7.1HZ, 3H), 1.16-1.33 (m, 4H) , 1.49 (t, J-7.7HZ, 2H) , 218 (ε 6H) ; ¹³ C NMR 7.8, 13.86, 22.49, 28.91, 31.76 48.56, 60.64; IR(neat) 837, 1173 cm ^"1 ; EIMS, m/z (relati

intensity) 123(68), 91(30), 81(100), 79(37), 67(47) ; HRK m/z (calc for C9K15: 123.1174) 123.1172; Anal. Calcd for C9H15I: C, 43.22; H, 6.05; I, 50.74; Found: C, 43.06; H, 6.07; I, 50.95.

Example 18 - l-Iodo-3-(l-methylpropyl)bicyclof1.1.1]pent

The same procedure aε in Example 17 εubstituting 2— iodopropane led to 4.0 g (32%) of εlightly brownish liqu (bp. 51-52 ^β C/0.8 mm Hg) which became brown upon standing: ^Η NMR 0.79 (d, J-6.7HZ, 3H), 0.85 (t, J~7.2Hz, 3H) , 0.93-1.03 (m, 1H), 1.34-1.41 (m, 1H) , 1.47-1.53 (m, 1H) ; ¹³ C NMR 8.29, 11.86, 15.89, 26.48, 36.57, 52.92, 58.91; IR(neat) 829, 847, 1177 cm ^""1 ; EIMS, m/z (relative intensity) 128(30), 127(20), 123(18), 81(100), 79(30), 77(25), 67(45), 55(43); HRMS, m/z (calcd for C9H15: 123.1174) 123.1171; Anal. Calcd ^' -fbr C9H15I: C, 43.22; H, 6.05; I, 50.74; Found: C, 42.99; H, 6.05; I, 51.00.

Example 19 - 3,3'-Diiodor2]εtaff ne

A 0.1 mole scale run using Procedure B was cannulate into a bproεilicate tube containing 0.5 equivalent of l,3-diiodobicyclo[1.1.13pentane. Pentane, or branched hydrocarbons were added to diεεolve the starting material then the εolution waε irradiated _, with a quartz lamp for l hr at 0*C. Product cryεtallized on the walls of the veεεel aε the reaction proceeded (followed by GC with <250 ^* C injector) and was iεolated by cryεtallization at 0 ^* C and recryεtallization from benzene to give clear needleε which decompoεed slowly on contact with the atmosphere and rapidly in direct sunlight: mp. dec. 120"C ^H NMR 2.18 (ε); ¹³ C NMR 6.35, 47.49, 59.73; Anal. Calcd for C ₁₀ H ₁₂ I ₂ : C,31.11; H, 3.13; I, 65.75, Found: C, 31.16 H, 3.16; I, 65.62. '

Example 20 - l-Iodo-3-phenylbicyclof1.1.1 pentane

1.28 ml (0.5 eq.) of iodobenzene were added to a εolution of propellane (10 mmol) generated via Procedure B. The colution waε transferred into a borosilicate tube and irradiated 1 hr, after which GC analyεiε of the εolution εhowed three new major peaks. The reaction mixture waε reduced in volume, high vacuum applied (40*C/0.2 mm Hg) to remove εtarting material and 1- iodobicyclo[1.1.13pentane. After these products were removed, l-iodo-3-phenylbicyclo[1.1.13pentane sublimed ou

• ^ff " i of the mixture (40-50'C/0.2 mm Hg) : "Tϊ NMR 2.06 (ε, 6H) ;

EIMS, m/z (relative intensity) 77(24), 127(25), 128(100),

143(91) . Resublimation produced an analytical εample having mp. 64-65'C. Recryεtallization from pentane at 0" gave a gummy solid. The liquid was diluted with pentane and recryεtallization at -78 ^* C, giving 1- phenylbicyclo[1.1.1]pentane: The solid, a mixture of 1- phenyl[2]εtaffane and 3-iodo-3'-phenyl[2]εtaffane by GCMS waε recryεtallized from benzene.

Example 21 — l,3-Diacetylbicyclori.l.l]pentane

A magnetically εtirred εolution of 0.1 moles of

Procedure A propellane and 9 ml of biacetyl were placed i a round bottom flaεk and photolyzed for 6 hourε. The solvents were then evaporated and the residue was distilled on Kugel-Rohr (80-85*C/0.4 mm Hg) giving 12.1 g of wet yellowiεh product. Cryεtallization from 25 ml heptane gave 8.80 g (58% yield) of large clear cryεtalε o 1,3-diacetylbicyclo[1.1.1]pentane: mp. 67-69*C; ^H NMR 2.14 (c, 6H), 2.24 ,-(ε, 6H) ; ¹³ C NMR 25.79, 43.10, 51.81, 205.01; EIMS, m/z (relative intensity) 152(1), 137(11), 109(43), 95(10), 43(100), 39(25), 28(54); HRMS, m/z (calc for C9H1202: 152.0837) 152.0839; Anal. Calcd for C9H1202: C, 71.02; H, 7.95. Found: C, 71.01; H, 7.97.

Example 22 — Formation of Telomerε: Adductε of diacetyldisulfide and propellane.

22.5 ml of diacetyldisulfide (0.5 eg.) were added a εolution 0.3 moleε of propellane in ether made via 5 Procedure A. The εolution was irradiated in a round bottom flaεk for leεε than 3 hr (to avoid product decomposition). Evaporation of solvent to 40.06 g cr mixture and refrigeration overnight produced 2.66 gm o oligomerε 2,3, and 4 in 20:51:16 ratio by GC after vac

10 filtration and waεh with cold MeOH. Short path diεtil tion of starting materialε and deco poεition productε (25-60*C/0.2 mm Hg) recovered diacetyl diεulfide. Dilution of the pot residue with an equal volume of methanol and icebath gave 5.31 gm of yellowish solid

15 containing mostly εecond oligomer. Further recryεtalli tionε and εubεequeπt εubli ationε (85*C/0.2 mm Hg) produced biε acetylthio[2]εtaffane: mp. 101 ^• C; TI NMR 2 (S, 12H) ; 2.26 (S, 6H) ; ¹³ C NMR 31.16, 37.99, 42.84, 53.35, 196.18; EIMS, m/z (relative intenεity) 43(100),

20 239(.5), 267(.02); Anal. Calcd for ₁₄ ^H ₁₈ ° ₂ ^S 2 ^{: C} ' ⁵⁹ - ⁵ 4 H, 6.42; O, 11.33, S, 22.70; Found: C, 59.43; H, 6.45; 22.61.

From both fractional and gradient sublimations, 3,3"-biε(acetylthio) [3]staffane were obtained: bp. 25 125-C/0.2 mm Hg; ^ NMR 1.47 (ε, 6H), 1.97 (ε, 12H),

2.25(S, 6H): ¹³ C NMR 31.12, 37.62, 37.83, 43.52, 48.38, 53.26, 196.20; Anal. Calcd for ^C ₁₉ ^H ₂ ⁰ 2 ^S 2 ^{: C} ' ^€5 * ^{48? H} ' 6.94; O, 9.18; S, 18.40. Found: C, 65.37; H, 6.98; S, 18.47.

30 Gradient εublimation gave 3,3'"-biε(acetyl- thio) [4]εtaffane: ^ NMR 2.25 (ε, 6H) , 1.96 (ε, 12H) , 1 (ε, 12H); ¹³ C NMR 31.22, 37.43, 37.95, 38.25, 43.81, 48.12, 53.39, 196.51; IR GM ^*"1 ; EIMS, m/z (relative intenεity) 43(100), 91(10), 341(0.14), 429(0.1); Anal. Calcd for.C ₂₄ H ₃₀ 0 ₂ S ₂ : C, 69.52; H, 7.29; 0, 7.72; S, 15.46. Found: C, 69.60; H, 7.32; S, 15.37.

The higher oligomerε decompoεed upon heating especially in the presence of impuritieε to give element εuifur and other products.

Example 23 - Addition of methyldiεulfide to propellane

To a εolution of 0.1 mole propellane in ether

(Procedure A) waε added 9.0 ml of methyldiεulfide. (1 eq.) The mixture waε photolyzed 3 hr in a round bottom flaεk (the process was cleaner when carried out in pentane, albeit lower yield.)

Starting material waε removed with solvent on the rotary-evaporator and Vigreaux diεtillation (57 ^* C/0.2 mm Hg) providing 13.0 g (85%) of 1,3-biεnethylthiobicy- clo[1.1.13pentane: i NMR: 1.99 (ε, 1H) , 2.04 (ε, 1H) ; ¹³ NMR 13.69, 40.98, 59.89. Second oligomer waε recryεtallized from pot reεidue with methanol/H ₂ 0 and sublimed to give 4% 3,3'-biε(methylthio) [23staffane: ^Η NMR 1.76 (ε, 2H), 2.05 (ε, 1H) ; ¹³ C NMR 13.47. GC preparation of "the εublimation reεidue allowed an analytical εample of 3,3"(biεmethylthio) [33εtaffane.

Example 24. — l-chloro-3- methaneεulfonylbicyclo[1.1.13pentane and l-chloro-3'- ethaneεulfonyl[2]εtaffane

A 0.1 mole run using Procedure A was photolyzed in a round bottom flask with magnetic stirring for 6 hours in the presence of 3.9 ml (0.5 eq.) of methane εulfonyl chloride and 0.1 g of benzoyl peroxide. GC shows firεt and εecond oligomerε. The εolution waε cooled to ice temperature and filtered to give 2.9 g of off-white powdery εolid of εecond oligomer which iε recryεtallizabl from heptane/CHCL ₃ : ^X H NMR 2.06 (ε, 6H) , 2.08 (ε, 6H) ,

2.81 (ε, 3H) ; ¹³ C NMR 56.24; Anal. Calcd for C^H^CIO^: C, 53, 54; H, 6.13; Cl, 14.37; S, 12.99. Found: C, 53.45 H, 6.18; Cl, 14.38; S, 13.03.

1—Chloro-3—methanesulfon lbicyclo[1.1.1]pentane wa obtained by Kugel-Rohr diεtillation of the filtrate and recryεtallization from heptane: IH NMR 2.54 (ε, 6H) , 2. (ε, 3H) ; 13C NMR 38.50, 42.14, 47.54, 48.83, 57.10.

Example 25 - l-chloro-3- benzenesulfonylbicyclo[1.1.1] entane

0.025 mole scale of Procedure A propellane synthesi was irradiated with 25 mg of benzoyl peroxide and 0.05 moles, 2 eq. 6.4 ml of benzene sulfonyl chloride for 6 h After rotoevaporation and diεtillation of starting material via Kugel-Rohr (up to 90*C at 0.5 mm Hg) , the yellow, crude product was treated with εilica gel, washe with 20 ml heptane, and recryεtallized from boiling heptane with toluene added for complete solubilization. second crop of crystalε yielded a total of 3.1 g of 95% pure colorleεε plateε ,(56% overall yield) ; p: IH KMR

2 2..4400((5S,, 6H), 7.59(t, 2H), ¹³ C NMR 136.10, 129-33, 57.04, 128.46.

Examples 28-31 - Photochemical Syntheεiε of BicycloT1.1.1]pentane-1,3-dicarboxylic Acid

It iε believed that the mechaniεm of the photoaddi- tion of biacetyl to [1.1.1 propellane iε repreεented by the following chain process, where the key step is a beta-fragmentation of an alkoxy radical:

CH.C0* + (1) •CH _j CO (X) •

(19)

CH_ (19) + (CH ₃ C0) ₂ >CH ₃ C0-A-C-0« (Y)

COCH

(20)

(20) - (7ά) + CK ₃ CO- (Z)

Irradiation of a εolution of biacetyl and [l.l.l]pr pellane in diethyl ether followed by hypobro ite oxidati of the reεulting diketone (7d) yielded the desired diaci (7b) in an overall yield of 52% baεed on the starting tetrahalide (18):

(22)

In the following examples, boiling pointε were . uncorrected. Melting pointε were determined using a Boetius PHMK05 apparatus with a microscope attachment at heating rate of 4*C/min. Melting pointε taken in a seal capillary were uncorrected ^' . K R spectra were run on a Nicolet NT-360 instrument in CDC1 ₃ solvent unlesε specified-otherwiεe. IR εpectra were recorded on a Nicolet 60SXR FTIR inεtruiaent. Maεε εpectra were taken a 5995 Hewlett-Packard inεtrument.

Example 26 - 1,3-Diacetylbicyclof1.1.1]pentane 89.1 g (0.30 mol) of (18) and 90 ml of pentane were placed in a 1-liter three-neck round bottom flaεk equipp with a mechanical εtirrer, septum and a εide arm connect -to.a dry-ice condenεer and fluεhed with dry argon. With vigorouε stirring, 510 _. ml of a 1.4 M εolution of methyllithium (Aldrich, salts-free) were added via cannu in 15 min at the dry ice - acetone bath temperature. Wh the addition was completed the bath was replaced by an i bath and the stirring was continued for 1 h. All volatileε were then vacuum-transferred to a cold trap equipped with a 1-liter round bottom flaεk receiver containing a magnetic εtirring bar. When almost dry salt appeared in the flaεk the transfer waε discontinued and t e apparatus waε again filled with argon. The receiver containing the propellane εolution was disconnected from

the cold trap, ctoppered with a septum and 27 ml of freshly distilled biacetyl were added from a syringe. T εolution waε εtirred at ice bath temperature and irradiated in a Pyrex veεεel for 8 h with a 450 W medium pressure Hanovia mercury lamp under dry argon. Volatile were evaporated and the semicryεtalline reεidue waε diεtilled on a Kugel-Rohr (80-85* C/0.4 mm Hg) , yielding 36.2 g of wet white to pale yellow cryεtalε. Cryεtalliz tion of the crude (7d) from heptane afforded 26.4 g of pure 4 in a 58% overall yield baεed on (18). Kp 67-69 ^* C ^H NMR delta 2.14 (ε,6H), 2.24 (s,6H) ; ¹³ C NMR delta

25.79, 43.10, 51.81, 205.01; IR (C-O) 1708; MS, m/z (relative intensity).152(1, M ⁺ ), 137(11), 109(43), 95(1C 43(100), 39(25); HEMS, m/z. (calcd for ^c _g H, ₂ 0 , 152.0837) 115522..00883399;; AAnnaall.. CCaallccdd ffoorr CgH^O.,: C, 71.02; H, 7.95. Found: C, 71.01; H, 7.97.

Example 27 - Bicyclo[l.l.l]pentane-l,3,dicarboxylic acid

26.4 g of (7d) was diεsolved in 125 al of dioxane a added over a period of 2 h to a εtirred εolution of εodi hypobromite prepared from 65 ml (1.25 mol) of bromine, 1 g (3.5 mol) of εodium hydroxide and 1050 al of water at 0-3*C After the addition of the diketone was completed, the reaction mixture was εtirred for 1 at 0*C, then 3 at room temperature and finally 1 h at 50"C. Next, 6 g εodium biεulfite were added and the reaction mixture was extracted with 3 X 300 ml of chloroform, acidified with 225 ml of concentrated hydrochloric acid and extracted with ether in a continuouε extraction apparatus for 30-50 h. The ether was evaporated, the reεidue waε dried under reduced preεεure and the crude product waε waεhed with 50 ml of boiling chloroform. Cold εuspension of the product waε filtered giving 24.6 g (90% yield) of the diacid (7b) p 305*C rapid dec, sealed tube (lit. mp >260*C βubl.), ¹³ C NMR (acetone-d ₆ ) 38.08, 53.04, 170.59.

Example 28 - Bicyclo[l.1.l]pentane-l,3-dicarboxylic acid via addition of acetaldehyde to [1.1.1]propellane

A εolution of [1.1.1]propellane in diethyl ether prepared by the above procedure (210 ml, 3% in [1.1.1]propellane according to integrated H NMR intensitieε) , 150 al of acetaldehyde and 0.4 g of benzoy peroxide was εtirred and irradiated aε above for 6 h. Evaporation of εolventε and acceεε acetaldehyde at reduc pressure (at the end, 50"C/0.8 mm Hg) furnished 15.06 g crude l-acetyl-3-(l-hydroxyethyl) bicyclo [1.1.13pentane in the form of a yeliowiεh oil (about 80% pure by GC) : NMR delta 1.05 (d, J-6.4 Hz, 3H) , 1.81 (d, J-9.0 Hz, 3H) 1.87 (d, J-9.0 Hz, 3H), 2.06 (ε, 3H) , 3.74 (q, J-6.4 Hz, IH) ; ¹³ C NMR (major peaks) 19.17, 25.95, 42.70, 43.41, 48.49, 66.21, 206.90; GC-MS, m/z (relative intensity)

139(24, M-Me), 121(63), 111(27), 95(30), 93(68), 91(59), 77(81), 71(100).

An attempt at purification by εhort-path diεtillati (100-115"C/0.4 am Hg) led to partial decomposition. Cru l-acetyl-3-(l-hydroxyethyl)bicyclo[1.1.13pentane (7.5 g) diluted with.25 ml of dioxane was slowly added to a vigorously εtirred solution of εodium hypobromite prepar by slow addition of 18.5 ml (0.36 mol) of bromine to a well stirred εolution of 40.0 g (1.0 mol) of sodium hydroxide in 300 ml of water. Temperature during preparation of the hypobromite aε well aε the addition o 3 was maintained below 5'C. The reaction mixture was stirred for 1 h at ice bath temperature, then 3 h at roo temperature and finally 1 h at 50*C. Exceεε hypobromite waε deεtroyed by addition of 5 g of sodium biεulfite, th mixture waε extracted with 3 x 50 ml of chloroform, acidified with 55 ml of cone. HC1 and the product waε extracted with ether for 10 hr. Ether waε evaporated, t reεidue waε dried under reduced preεεure and the crude diacid (7b) waε washed with 10 ml of boiling chloroform. Filtering off the cold suspension gave 2.76 g (35% yield of the product.

Example 29 - l _r 3-Biε(chlorocarbonyl)bicyclori.l.1]pentan

24.6 g (0.157 mol) of the diacid (7b) and 45 ml of thionyl chloride were refluxed until a clear εolution was formed (about 10 h) . Exceεs thionyl chloride was evaporated and the crystalline reεidue was distilled on K geϊ-Rohr (120*C/12 mm Hg) giving 26.92 g (89% yield) o product: mp 55-57*C; ^H NMR delta 2.58 (ε) ; ¹³ C NMR delta 44.57, 54.80, 169.55; IR (C-O) 1794; MS, m/z (relative intensity) 159(1.4, M-Cl), 157(4.4, K-Cl), 131(1.3), 129(4.0), 103(11.6), 101(32.4), 65(100); HRMs) m/z (calcd for C ₇ H ₆ C10 ₂ : 157.0056) 157.0054. Anal. Calcd for C ₇ H ₆ C1 ₂ 0 ₂ : C, 43.55; H, 3.13; Cl, 36.74; Found: C, 43.48 H, 3.14; Cl, 36.76.

Example 30 — Dimethyl bicyclo[1.1.1 pentane-l,3- dicarboxylate

26.92 g (0.139 mol) of the product in Example 29 was slowly added to 75 al of εtirred anhydrous methanol. Whe the addition was completed the mixture waε refluxed for 3 ain. Evaporation of methanol gave a cryεtalline εolid which after short-path diεtillation (125-130 ^* C/12 mm Hg) gave 25.24 g (99% yield) of product: mp 92 ^* C; ^X H NMR delt 2.30 (ε, 6), 3.67 (ε, 6H) ; ¹³ C NMR delta 37.46, 51.45, 52.68, 169.31; IR: 1739, 1211; MS, m/z (relative intenεity) 153(31, M-OMe) , 152(57), 125(51), 124(80), 96(100), 66(70), 64(59); HEMS, a/-z (calcd for CgH^: 153.0549; Anal. Calcd for C ₉ H ₁₂ 0 ₄ : C, 58.69; H, 6.57; Found: C, 58.78; H, 6.58.

Example 31 - 3-Methoxycarbonylbicyclo[l.l.lJpentane-l- carboxylic acid

To a gently refluxed and εtirred solution of 25.24 (0.137 mol) of the dimethyl ester product of Example 30 200. l of aethanol, a εolution of 5.50 g (0.137 mol) of sodium hydroxide in 50 ml of methanol waε added during 1. hr. When the addition waε completed the mixture was εtirred and refluxed for 1 h. Methanol was evaporated a the white εodium εaltε were vacuum dried. The saltε wer disεolved in 150 al of water, unreacted Example 30 produ waε extracted with 4 ;x 50 al of methylene chloride (3.00 of Example 30 product was recovered) and the aqueouε pha waε acidified with 12 ml of concentrated hydrochloric acid. The product waε extracted with 4 x 50 ml of methylene chloride, and the extractε were dried with εσdium εulfate. Evaporation of the εolvent gave 18.12 g (88% yield corrected for recovered Example 30 product) o crude product (mp 137.5-140*C) . Cryεtalization from heptane-chloroform gave pure product: mp 139.5-140 ^* C (lit. ¹ mp 139.5-140.2'C); hi NMR delta 2.35 (ε, 6H0, 3.6

(ε, 3H); ¹³ C NMR delta 37.43, 51.80, 52.69, 169.61, 174.73; MS, m/z (relative intenεity) 153(1, M-OH) , 152(4) 139(13), 138(14), 125(10), 124(16), 111(17), 110(31), 96(53), 93(22), 83(29), 82(100), 67(52), 66(62), 65(98).

2. Liquid Crystals

Certain diεubstit ted oligomerε (2) of [1.1.13propellane exhibit meεogenic behavior, for exampl (2a,n ^« =3) and (2q,n-=3). (2a,n=3) has been found to have the following characteristics: K 136 S _G 166N 194 I, while (2q,n-=3) has the following: K 55 S_ 95 I.

B

Theεe compoundε are representative of a potentially large claεε of liquid cryεtalε which promiεe unique and - uεeful phyεical propertieε. Cryεtallographic data εhow the length of the rigid core of (2a,n-=3) to be around 8.55 A, comparable to biphenyl, with a value of 2.49 A for the diameter of a cylinder on which the carbon atoms are located.

A related liquid cryεtal provided by the present invention has the following formula:

X-@-OCO-τ -COO— ©—X (a) X - OMe K 143 N 145.5

(b) OBu K 129 N 144 I

(24)

These compounds aay be created by linking together various liquid crystal building blocks or precursors. Examples of εuch building blocks are the following:

A, CN, COOMe, etc.

^

where X «= COOH or OH.

Example 32 - Preparation of Liquid Crystal Building Block

Exemplary preparations of liquid crystal building blocks in accordance with the present invention are εhown below.

(AcS) ₂ OH~,H ⁺ (1) (2r) v(2ε) (BB)

RI + (1) *(7e) = (7f)

(CC)

Bu_SnH, biacetyl

_Whe re _R iε, for example, an alkyl, a cycloalkyl (e.g. R—(H-,R'- -)* n aryl (e.g. R'~<§>- ), or an iodine substituted alkyl, cycloalkyl, or aryl.

(27)

(27)may then be uεed aε a (7e) in reaction (CC) to produce a (7f) precurεor.

-Br ₂ /OH

(7f) * 7g) (DD)

AcOH

(MeCO) ₂ ^H 2°2 ( n1) ... .. . .... ». C(77άd)\ .(7i) (FF)

IfO AcOH

Br ₂ /OH

(7d). →- (7b)- -H7j ) (GG)

(7j ) + (7h) — R — A- (HH)

(23)

Example 33 - Preparation of Liquid Crystalε

Exemplary preparations of liquid.cryεtalε in accordance with the preεent invention are εhown below.

(23) + —Λ-COO-A-R (II)

(24)

(25)

(23) may alεo be reacted with 1,4-cyclohexanol or 1,4-butanol to produce corresponding liquid crystals.

Preferably, R does not have an amine, εulfur, or hydroxyl group, εince the presence of εuch a group generally makes the intermediate compound (7e) unstable.

Example 34 - Exemplary Liquid Crystals

Exemplary liquid cryεtalε provided by the present invention are εhown in the following chart.

(6)

m X n B

(a) CH ₃ C0 0 s 3 s 0 COCH ₃ H (b) 0 OC 1-3 CO 0 <§ -OMe H,F _/ C1, (c) 00C

^C 5 ^H 1 .1-3 cob 0 <J5>- CN H (d)

^C 5 ^H 1 CH ₂ CH ₂ 1 COO 0 <§>~ ^' CN H (e)

^C 5 ^H 1 CH ₂ ^: CH ₂ 1 COO 1 <§>-CN H (f) 0

^C 5 ^H 1 COO 2 OOC 2

^0C 5 ^H 11 H (9) ^C 5 ^H 1 -<H> COO 1 OOC 1 <S> ^C 5 ^H 11 H (h) ^C 5 ^H 1 ^" <H 00C 1 COO 1 S^c _5Hl1 H,C1,P (i) C ₅ H ₁ - H> COO(CH ₂ ) _1-3 0 OCO 1

< ^6H 2>1-3 <H C ₅ H (j ) ^C 5 1 ooc -ζn o COO 1

^C 5 ^H 11 (k) ^C 5 ^H 1 00C 1 COO o ®-CN H

m X n B

(o) ^C 5 ^H lf ^"OCO i (CH ₂ CH ₂ ) 1 COO 1 ^C 5 ^H 11 H

(q) C ₅ H S 2 OOC 1 COO 2 ^SC 5 ^H 11 H

(r) Bu 0 s 3 s 0 Bu II