ARYLCYC OBUTENYL AMIDO ALKENOIC ACIDS AND SALTS THEREOF

This invention relates to arylcyclobutenyl amido alkenoic acids and salts thereof.

In recent years the search for high perfor¬ mance materials, especially high temperature-resistant polymers, has gained momentum. In order for a material to have stability at high temperatures, it must fulfill several requirements including a high melting or soften¬ ing temperature, a high modulus or rigidity, a resistance to solvent and chemical degradation, and toughness. The intrinsic thermal and oxidative stability of aromatic structures has long been recognized, and a variety of polymers have been made in which benzene rings are linked together by various connecting groups. Among the more stable aromatic polymers that fulfill the requirements of high temperature resistance are the polybenzimida- zoles, the polybenzoxazoles and the polyimides. Of these polymers, the polyimides have had the most inter¬ est.

The major difficulty encountered in the commercial development ^: of these materials is that they are usually obtained in the form of a powder which cannot be readily fabricated into useful objects.

The polyimides prepared from aliphatic diamines and aromatic carboxylic acids are gener¬ ally soluble and thermoplastic. Aliphatic poly¬ imides have been prepared from bis(dienophiles) and a bis diene. Such reactions often involve gas evolution.

Aromatic polyimides, such as polypyromel- litimides, have a spectrum of superior properties. These polyimides may be prepared by the reaction of an aromatic dianhydride with an aromatic diamine to give a soluble polyamic acid, which on cyclodehydra- tion gives the insoluble desired product.

High performance plastics reduce the weight of mechanical components, and not just by virtue of their densities. Their high performance properties allow greater design stresses, and often elements can be downsized accordingly. In recent years, aromatic polyimides have become widely accepted as premium, high performance engineering plastics. These resins are well-known for having excellent properties at elevated temperatures (i.e., chemical resistance) but are also costly. Histori¬ cally, polyi ide resins are difficult to fabricate into objects other than fibers and films. The most

common methods of manufacturing parts having the highest strength and temperature properties are hot compression-molding, machining from hot-compression molded or extruded rod, and direct forming (a pro- cess similar to the powder-metallurgy processes) . Given the synthetic and fabrication difficulties, a new route to polyimides is desirable.

A further problem with the preparation of certain polyimides is the need for the use of catalysts, initiators or curing agents. The pres¬ ence of such compounds often results in the prepa¬ ration of impure polymeric compositions. Further, the presence of such compounds often results in undesirable properties in such polymeric co posi- tions. Many of the monomers used to prepare poly¬ imides are water-insoluble. What is needed are monomers which prepare polyimides wherein the poly¬ mers can be easily processed, for example, fabri¬ cated into useful objects. What is further needed are monomers which can be polymerized in a manner such that no volatile gas is evolved. What is fur¬ ther needed are monomers which can be polymerized without the need for catalysts, curing agents or initiators. Monomers which are water-soluble are needed.

The invention is a compound which comprises an amido alkenoic acid or a water-soluble salt thereof and an arylcyclobutene moiety, characterized in that the cyclobutene moiety is fused to the aryl radical, and wherein the amide nitrogen is connected to the aryl radical of the arylcyclobutenyl moiety by a bridging member or a direct bond.

The novel compounds of this invention are useful in preparing thermoset polymers. These com¬ pounds are also intermediates in the preparation of N-substituted arylcyclobutenyl unsaturated cyclic imides. The cyclic imides are useful in preparing thermoset polymers.

The salts of the arylcyclobutenyl amido alkenoic acids of this invention are water-soluble. These compounds can be polymerized from aqueous solution. Alternatively, the monomers can be depos¬ ited on a substrate surface using an aqueous solu¬ tion of such compounds. The N-substituted arylcy¬ clobutenyl unsaturated imides prepared from the novel compounds of this invention are water-insol- uble. The polymers prepared from both classes of compounds are similar in structure and properties.

The novel compounds of this invention are easily processable into useful articles. Fur¬ thermore, in order to prepare the polymers of these monomers, there is no need for catalysts, initiators or curing agents.

In general, the compounds of this inven¬ tion comprise amido alkenoic acids or water-soluble

salts thereof which are N-substituted with aryl¬ cyclobutene moieties. In such arylcyclobutene moi¬ eties the cyclobutene ring is fused to the aromatic radical. The nitrogen atom of the amide is con- nected to the aryl radical of the arylcyclobutene moiety by a bridging member or a direct bond. The amido alkenoic acid or water-soluble salt thereof can be substituted with hydrocarbyl, hydrocarbyl- oxy or hydrocarbylthio subsτfituents. The aryl radical on the arylcyclobutene moiety can be sub¬ stituted with electron-withdrawing groups, elec¬ tron-donating groups, hydrocarbyl groups, hydro- carbyloxy groups or hydrocarbylthio groups. The cyclobutene ring may be substituted with electron- -withdrawing groups.

The amido alkenoic acid can be any alkene which is substituted with amide and carboxylic acid moieties, or a water-soluble salt of the carboxylic acid. In one preferred embodiment the amido alkenoic acid is capable of cyclization when exposed to dehy¬ dration conditions, and may be substituted as described hereinbefore.

Water-soluble salt of the amido alkenoic acid refers herein to the compounds of this inven- tion in which the.carboxyl moiety of the alkenoic acid is converted to a water-soluble salt by replac¬ ing the hydrogen atom with the cation from a base. • Preferred bases from which the cation is derived include alkali metal bases, alkaline earth metal bases, ammonia, primary or secondary amines and the

like. More preferred bases include ammonia, and primary or secondary amines. Ammonia is the most preferred base.

It is preferable that the olefinic unsatu- ration be adjacent to either the acid or amide car- bonyl moiety. In one more preferred embodiment, the amido alkenoic acid has 2 carbon atoms between the amide and carboxylic acid carbon atoms. In partic¬ ular, it is an amido butenoic acid. Preferably, the substituents which may be on the carbon atoms of the alkenoic chain are C _1-2Q alkyl, C., _2Q alkoxy, C _2o alkylthio, C ₆ _ _2Q aryl, C ₆ _ ₂₀ aryloxy, C ₆ _ _2Q arylthio, ^C 7-20 ^a ^- ^kar y ¹ ' ^C 7-20 ^alk aryloxy, ^C 7_20 ^a lkarylthio, 7-20 ^ara ^ ^k yl' ^C 7-20 ^aral ^oxy ^or 7-20 ^^^Yl^i? ^• More preferred substituents include C _^ g alkyl, with C- - alkyl being most preferred.

The arylcyclobutene moiety can be any aro¬ matic radical which has a cyclobutene ring fused to one of the aromatic rings. The term "aryl" refers herein to any aromatic radical. Preferred aromatic radicals include benzene, naphthalene, phenanthrene, anthracene, a biaryl radical, or two or more aromatic radicals bridged by alkylene or cycloalkylene moi¬ eties. More preferred aromatic radicals include ben- zene, naphthalene, biphenyl, binaphthyl or a diphenyl- alkylene or a diphenylcycloalkylene compound. The most preferred aromatic radical is benzene.

The aryl radical can be substituted with electron-withdrawing groups, electron-donating groups,

hydrocarbyloxy groups, hydrocarbyl groups or hydrocar¬ bylthio groups. Electron-withdrawing groups refer herein to cyano, carboxylate, hydrocarbylcarbonyloxy, nitro, halo, hydrocarbylsulfinyl or hydrocarbylsulfo- nyl groups. Electron-donating groups refer herein to amino groups. Preferred substituents on the aryl radical include C,_ _2Q alkyl, C _1-2Q alkoxy, C ₁ _ _2Q alkylthio, C ₆ _ _2Q aryl, C ₆ _ _{2 Q} aryloxy, C _6-2Q aryl- thio, C__ ₂₀ alkaryl, C„_ ₂₀ alkaryloxy, ^C _ ₂ o ^alJζ " arylthio, C _7-2Q aralkyl, ^ ₇ _ ₂₀ ^aralkoχ Y' 7-20 aralkylthio, cyano, carboxylate, hydrocarbylcar¬ bonyloxy, nitro, halo, hydrocarbylsulfinyl, amino or hydrocarbylsulfonyl. More preferred substitu¬ ents on the aryl radical include C,_ _2Q alkyl, halo, nitro or cyano. The most preferred substituents on the aryl moiety include C, - alkyl, halo, nitro or cyano.

The cyclobutene ring may be substituted with electron-withdrawing groups, wherein electron- -withdrawing groups are described hereinbefore.

Preferred substituents on the cyclobutene ring are cyano, carboxylate, hydrocarbylcarbonyloxy, nitro, halo, hydrocarbylsulfonyl or hydrocarbylsulfinyl. More preferred substituents include halo, nitro or cyano groups; with cyano groups being most preferred.

The arylcyclobutene moieties and amido alkenoic acid moieties are connected herein by a direct bond or- bridging member. Bridging members comprise (1) a polyvalent inorganic moiety,- or (2) a polyvalent organic moiety. The bridging member or

direct bond connects the arylcyclobutene moieties through the aryl radical to the amido alkenoic acid moieties through the amide nitrogen.

Polyvalent inorganic moiety refers to any inorganic moiety which is capable of bonding to an aryl radical and an amide nitrogen. Such polyva¬ lent inorganic moieties can be covalently or ionic- ally bonded to the aromatic radical and the amide nitrogen atom. Examples .of polyvalent inorganic moieties include oxygen, phosphorus, phosphorus oxide, sulfur, nitrogen, polysiloxanes, polyvalent metals, sulfoxide, sulfone, a polyvalent metal bound to a polyvalent oxygenated moiety wherein the polyvalent oxygenated moiety can be further bound to an aryl radical (for example, a polyvalent car¬ boxylate salt) . Preferred polyvalent inorganic moi¬ eties include oxygen, sulfur, polysiloxanes, and polyvalent metals bound to polyvalent oxygenated moieties.

The polyvalent, organic bridging member can be any polyvalent organic moiety which can link an aryl radical to an amide nitrogen.

Preferred bridging members are the diva¬ lent organic radicals.which are bonded to the nitro- gen of the amide and the aryl radical of the arylcy¬ clobutene moiety. The divalent organic radical use¬ ful as a bridging member is any divalent organic radical which is capable of being bonded to both the nitrogen of an amide and an aryl radical. The

divalent organic radical is preferably a hydrocar- bylene, hydrocarbyleneamido, hydrocarbylenecarbonyl- oxy, hydrocarbyleneoxy, hydrocarbylenethio, hydro- carbylenesulfinyl or hydrocarbylenesulfonyl radical. More preferred divalent organic radicals are alkyl¬ ene, arylene, alkylene-bridged polyarylene, cyclo¬ alkylene-bridged polyarylene, alkenylene-bridged polyarylene, alkyleneamido, aryleneamido, alkylene- -bridged polyaryleneamido, cycloalkylene-bridged polyaryleneamido, alkenylene-bridged polyarylene- . amido, alkylenecarbonyloxy, arylenecarbonyloxy, alkylene-bridged polyarylenecarbonyloxy, cycloal¬ kylene-bridged polyarylenecarbonyloxy, alkenylene- -bridged polyarylenecarbonyloxy, alkyleneoxy, aryleneoxy, alkylene-bridged polyaryleneoxy, cyclo¬ alkylene-bridged polyaryleneoxy, alkenylene-bridged polyaryleneoxy, alkylenethio, arylenethio, alkylene- -bridged polyarylenethio, cycloalkylene-bridged poly¬ arylenethio, alkenylene-bridged polyarylenethio, alkylenesulfinyl, arylenesulfinyl, alkylene-bridged polyarylenesulfinyl, cycloalkylene-bridged polyaryl- enesulfinyl, alkenylene-bridged polyarylenesulfinyl, alkylenesulfonyl, arylenesulfonyl, alkylene-bridged polyarylenesulfonyl, cycloalkylene-bridged polyaryl- enesulfonyl or alkenylene-bridged polyarylenesulfonyl. Even more preferred divalent organic radicals include alkylene, arylene, alkylenecarbonyloxy, arylenecar¬ bonyloxy, alkyleneamido, aryleneamido, alkyleneoxy, aryleneoxy, alkylenethio or arylenethio. Most pre- ferred divalent organic radicals include alkylene and arylene radicals.

Preferably, the aryl moiety and, cyclic imide are connected by a direct bond or a bridging member which comprises an alkylene, arylene, alkyl¬ ene-bridged polyarylene or cycloalkylene-bridged polyarylene; and more preferably a direct bond or a bridging member which comprises an alkylene or, arylene moiety. Most preferably the amide nitrogen and the aryl radical are connected by a direct bond.

Preferred arylcyclobutenyl amido alkenoic acids or water-soluble salts thereof correspond to the formula

wherein

Ar is an aromatic radical;

R is separately in each occurrence a hydro¬ carbyl, hydrocarbyloxy, hydrocarbylthio, electron-

-donating or electron-withdrawing group;

R 2 i•s separately in each occurrence hydro¬ gen or an electron-withdrawing group;

X is an alkenylene moiety which can be sub¬ stituted with one or more hydrocarbyl, hydrocar¬ byloxy or hydrocarbylthio groups;

Y is a direct bond or divalent organic moi¬ ety;

-11-

Z is hydrogen or a cation derived from ammonia, a primary or secondary amine, an alkali metal base or alkaline earth metal base; and a is an integer of between 0 and 3, inclusive.

More preferred arylcyclobutenyl amido alkenoic acids or water-soluble salts thereof include those which correspond to the formula

tl

0

wherein

Ar is an aromatic radical;

R is separately in each occurrence a hydrocarbyl, hydrocarbyloxy, hydrocarbylthio, an electron-donating or electron-withdrawing group; ₂ R is separately m each occurrence hydro¬ gen or an electron-withdrawing group;

R 3 is separately m each occurrence hydro¬ gen, a hydrocarbyl, hydrocarbyloxy or hydrocar¬ bylthio group;

Y is a direct bond or a divalent organic radical;

Z is hydrogen or a cation derived from ammonia, a primary or secondary .amine, an alkali metal base or alkaline earth metal baser and a is an integer of between 0 and 3, inclusive.

. ^' In an even more preferred embodiment, the arylcyclobutenyl amido alkenoic acid or water- -soluble salt thereof corresponds to the formula

wherein

R is separately in each occurrence a hydrocarbyl, ^' hydrocarbylthio, hydrocarbyloxy, electron-withdrawing or electron-donating group;

R 2 i.s separately m each occurrence hydro¬ gen or an electron-withdrawing group;

R 3 i.s separately in each occurrence hydro¬ gen, hydrocarbyl, hydrocarbyloxy or hydrocarbyl¬ thio;

Y is a direct bond or a divalent organic radical,-

Z is hydrogen or a cation derived from ammonia, a primary or secondary amine, an alkali metal base or alkaline earth metal base; and a is an integer of between 0 and 3, inclu¬ sive.

In the above formulas, R is preferably

^C l-20 ^al y ¹ ' ^C i-20 ^alkox Y' ^C i-20 ^alk Y ^ltnio ' ^C 6-20 aryl, C ₆ _ _2Q aryloxy, C _6-2Q arylthio, C ₇ _ _2Q alkaryl,

^C 7-20 ^a l ^kar Y ^lox Y' ^c 7__20 ^alkar Y ^1'tll i ⁰ ' ^C 7-20 ^aralk Y ¹ ' ^C 7-20 ^aralkoχ Y' ^C 7_20 ^ara l ^k Y ^ltiι i- ⁰ ' cyano, carboxyl ^¬ ate, hydrocarbylcarbonyloxy, nitro, halo, hydrocar¬ bylsulfinyl, hydrocarbylsulfonyl or amino. R is more preferably Ci ₀ alkyl, halo, nitro or cyano. Most preferably R is C, - alkyl, halo, nitro or cyano.

₂

R is preferably hydrogen, cyano, carbox¬ ylate, hydrocarbylcarbonyloxy, nitro, halo, hydro- carbylsulfonyl or hydrocarbylsulfinyl. R 2 i.s more preferably hydrogen, halo, nitro or cyano. R 2 i•s even more preferably hydrogen or cyano and most preferably hydrogen.

3 R is preferably hydrogen, C-, _2Q alkyl,

^C l-20 ^alkoχ Y' ^C i-20 ^alχ Y ^ltllio ' ^C 6-20 ^ar Y ¹ ' ^C 6-20 aryloxy, C ₆ _ ₂ o arylthio, ^C 7_2o ^alkar Yl' ^C 7_20 ^alk ~ aryloxy, ., _2Q alkarylthio, C_ _2Q aralkyl, ₇ _ _2Q aralkoxy or C- _2Q aralkylthio. R is more prefer¬ ably hydrogen or C-i ₂ 0 alkyl. R is even more preferably hydrogen or C., , alkyl and most pref¬ erably hydrogen.

In the above formulas, Y is preferably a direct bond, a hydrocarbylene, hydrocarbyleneamido, hydrocarbylenecarbonyloxy, hydrocarbyleneoxy, hydro- carbyleneamino, hydrocarbylenecarbonyl, hydrpcarbyl- enethio, hydrocarbylenepolythio, hydrocarbylenesul¬ finyl or hydrocarbylenesulfonyl. Y is more .prefer¬ ably a direct bond, alkylene, arylene, alkylene- -bridged polyarylene, cycloalkylene-bridged poly¬ arylene, alkyleneamido, aryleneamido, alkylenecar- bonyloxy, arylenecarbonyloxy, arylenecarbonyl, alkyl- enecarbonyl, aryleneoxy, alkyleneoxy, aryleneamino, alkyleneamino, alkylenethio, alkylenepolythio, aryl¬ enethio, arylenepolythio, arylenesulfinyl, alkylene- sulfinyl, arylenesulfonyl or alkylenesulfonyl. Y is most preferably a direct bond, alkylene or arylene.

In the above formulas, Z is preferably hydrogen, a cation derived from ammonia, an alkali metal base, an alkaline earth metal- base, or an amine. More preferred cations are those derived from ammonia, an alkali metal base, or an amine.

Even more preferred cations are (R 6) -NΦ(H), wherein

6

R is C, , _Q alkyl br C-, , _Q aryl; a is 0 to 3; b is 1 to 4; with the proviso that a+b=4. The most pre¬ ferred cation is an ammonium ion.

In the formulas described hereinbefore,

Ar is preferably a benzene, naphthalene, phenan- threne, anthracene or biaryl radical, or two or more aromatic radicals bridged by alkylene moieties. Ar is more preferably benzene, naphthalene, biphenyl, binaphthyl or a diphenylalkylene. Ar is more pref¬ erably a benzene radical.

Hydrocarbyl means herein an organic rad¬ ical containing carbon and hydrogen atoms. The term hydrocarbyl includes the following organic radicals: alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, aliphatic and cycloaliphatic aralkyl and alk¬ aryl. Aliphatic refers herein to straight- and branched-, and saturated and unsaturated, hydrocar-- bon chains, that is, alkyl, alkenyl or alkynyl. Cycloaliphatic refers herein to saturated and unsat- urated cyclic hydrocarbons, that is, cycloalkenyl and cycloalkyl. The term aryl refers herein to biaryl, biphenylyl, phenyl, naphthyl, phenanthra- nyl, anthranyl and two aryl groups bridged by an alkylene group or alkenylene group. Alkaryl refers ^■ herein to an alkyl-, alkenyl- or alkynyl-substi- tuted aryl substituent wherein aryl is as defined hereinbefore. Aralkyl means herein an alkyl, alkenyl or alkynyl group substituted with an aryl group, wherein aryl is as defined hereinbefore. ^c ι_ ₂₀ alkyl includes straight- and branched-chain methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nona- decyl and eicosyl groups. ^c _ι _ ₅ alkyl includes methyl, ethyl, propyl, butyl and pentyl.

Cycloalkyl refers to alkyl groups con¬ taining one, two, three or more cyclic rings. Cyclo¬ alkenyl refers to mono-, di- and polycyclic groups containing one or more double bonds. Cycloalkenyl also refers to cycloalkenyl groups wherein two or more double bonds are present.

Hydrocarbylene herein refers to a diva¬ lent radical containing carbon and hydrogen atoms and is analogous to the hydrocarbyl radicals described hereinbefore with the single difference that the hydrocarbylene radical is divalent.

-.. Hydrocarbyleneamido refers herein to a divalent radical wherein a hydrocarbylene radical is bonded to an amido group, and corresponds to ^' the formula

;. • 0

R ⁵

wherein R 4 is a hydrocarbylene radical and R5 i•s hydrogen or a hydrocarbyl radical.

Hydrocarbyleneoxy refers herein to a divalent radical in which a hydrocarbylene radical is bonded to a divalent oxygen atom and corresponds to the formula -R 4-O- wherein R4 i.s as defined here¬ inbefore.

Hydrocarbylenecarbonyloxy refers to a hydrocarbylene moiety which is bonded to a carbonyl moiety which is further bonded to a divalent oxygen atom and corresponds to the formula

4 " -R -C0-

wherein R 4 is as defined hereinbefore.

Hydrocarbyleneoxycarbonyl refers to a hydrocarbylene moiety which is bonded to a divalent oxygen atom, wherein the oxygen atom is further bonded to a carbonyl moiety and corresponds to the formula

0

wherein R 4 is as hereinbefore defined.

Hydrocarbylenethio refers herein to a radical in which a hydrocarbylene radical is further bonded to one or more sulfur moieties and corresponds to the formula -R 4-(S) - wherein R4 i.s as hereinbe-

P fore defined, and wherein p is an integer of between

1 and 3.

Hydrocarbyleneamino refers herein to a hydrocarbylene radical bonded to .an amino moiety _^ and generally corresponds to the formula

-R ⁴ -N-

wherein R ⁴ and R ⁵ are as defined hereinbefore.

Hydrocarbylenesulfinyl refers herein to a hydrocarbylene moiety bonded to a sulfinyl moiety and generally corresponds to the formula

^" wherein R 4 is as hereinbefore defined.

Hydrocarbylenesulfonyl generally corre¬ sponds to a radical in which a hydrocarbylene radi- cal is bonded to a sulfonyl radical and corresponds to the formula

II

O

4 . wherein R is as hereinbefore defined.

Wherein the bridging member is a hydro- carbyleneamido, hydrocarbyleneoxy, hydrocarbylene- amino, hydrocarbylenethio, hydrocarbylenecarbonyl¬ oxy moi ^' ety, the amido, amino, oxy, thio, sulfinyl or sulfonyl moiety is preferably bonded to the aryl portion of the arylcyclobutene.

Alkylene-bridged polyarylene, alkenyl- ene-bridged polyarylene and cycloalkylene-bridged polyarylene refers herein to divalent radicals con¬ taining two or more arylene moieties wherein the

arylene moieties are connected by alkylene, alkenyl- ene or cycloalkylene moieties (bridges), respectively. In one preferred embodiment, such bridging members generally correspond to the formula

wherein Ar is as hereinbefore defined; R is sepa¬ rately in each occurrence an alkylene, cycloalkylene or alkenylene radical; r is independently in each occurrence 0 or 1; and q is 1 or greater. R 11 is preferably a C., _2Q alkylene or C-, _2Q alkenylene. R is more preferably C,._ ₁₀ alkylene or C^^ _Q alkenylene. R is even more preferably C _1-4 alkylene or C- . alkenylene, with -CH=CH- being most preferred. Preferably q is an integer of between 1 and 20, most preferably an integer of between 1 and 10. In a more preferred embodiment, the aromatic radical hydrocarbon poly-yl bridging member corresponds to the formula -CH=CH- -CH=CH wherein q is as hereinbe- fore defined.

Examples of preferred arylcyclobutenyl amido alkenoic acids include N-benzocyclobutenyl- methyl amido butenoic acid, N-benzocyclobutenyl- ethyl amido butenoic acid, N-[(bicyclo(4.2.0)octa- -1,3,5-trien-3-ylamino)methyl]maleamic acid, N-ben- zocyclobutenylpropyl amido butenoic acid, N-benzo- cyclobutenylbutyl amido butenoic acid, N-benzocyclo- butenylhexyl amido butenoic acid, N-benzocyclobu- tenylphenyl amido butenoic acid, N-benzocyclobuten- ylbiphenyl amido butenoic acid, N-benzocyclobutenyl-

amidomethyl amido butenoic acid, N-[bicyclo(4.2.OJ- octa-l^S-trien-S-ylaminol^-oxoethyljmaleamic acid, N-benzocyclobutenylamidoethyl amido butenoic acid, N-benzocyclobutenylamidopropyl amido butenoic acid, N-benzocyclobutenylamidobutyl amido butenoic acid, N-benzocyclobutenylamidopentyl amido butenoic acid, N-benzocyclobutenylamidohexyl amido butenoic acid, N-benzocyclobutenylamidophenyl amido butenoic acid, N-benzocyclobutenylamidobiphenyl amido butenoic acid, N-benzocyclobutenyloxycarbonylmethyl amido butenoic acid, N-[(bicyclo(4.2.0)octa-1,3,5-trien-3-yloxy]- -z-oxoethyl]maleamic acid, N-benzocyclobutenyloxy- carbonylethyl amido butenoic acid, N-benzocyclobu- tenyloxycarbonylpropyl amido butenoic acid, N-ben- zocyclobutenyloxycarbonylbutyl amido butenoic acid, N-benzocyclobutenyloxycarbonylpentyl amido butenoic acid, N-benzocyclobutenyloxycarbonylhexyl amido butenoic acid, N-benzocyclobutenyloxycarbonylphenyl amido butenoic acid, N-benzocyclobutenyloxycarbonyl- biphenyl amido butenoic acid, N-benzocyclobutenyl- thiomethyl amido butenoic acid, N-benzocyclobutenyl- thioethyl amido butenoic acid, N-[2-(bicyclo(4.2.0)- octa-1,3,5-trien-3-ylthio)ethyl]maleamic acid, N-benzocyclobutenylthiopropyl amido butenoic acid, N-benzocyclobutenylthiobutyl amido butenoic acid, N-benzocyclobutenylthiopentyl amido butenoic acid, N-benzocyclobutenylthiohexyl amido butenoic acid, N-benzocyclobutenylthiophenyl amido butenoic acid, N-benzocyclobutenylthiobiphenyl amido butenoic acid, N-benzocyclobutenyloxymethyl amido butenoic acid, N-benzocyclobutenyloxyethyl amido butenoic acid, N-[2-(bicyclo(4.2.0)octa-l,3,5-trien-3-yloxy)ethyl]- maleamic acid, N-benzocyclobutenyloxypropyl amido

butenoic acid, N-benzocyclobutenyloxybutyl amido butenoic acid, N-benzocyσlobutenyloxypentyl amido butenoic acid, N-benzocyclobutenyloxyhexyl amido butenoic acid, N-benzocyclobutenyloxyphenyl amido butenoic acid, N-benzocyclobutenyloxybiphenyl amido butenoic acid, and the like.

The arylcyclobutene moieties can be pre¬ pared by several synthesis schemes.

In one synthesis scheme, an alkyl-sub- stituted aromatic compound which is further substi¬ tuted with an aryl deactivating substituent is chloroalkylated in a position ortho to the alkyl group. In the preferred embodiment wherein the aromatic compound is benzene, the starting material corresponds to the following formula

wherein R 1 and R2 are as defined hereinbefore; R1 is any aryl deactivating substituent such as hydrocarbyloxy- carbonyl, carboxamide, hydrocarbylcarbonyl, car¬ boxylate, halocarbonyl, nitrile, nitro, sulfone, or sulfoxide group; and c is an integer of 0, 1, 2, or 3. The alkyl N-substituted aromatic compound is chloroalkylated by contacting the alkyl aromatic com ound with a chloroalkylating agent and thionyl

chloride in the presence of an iron chloride cata¬ lyst so as to result in a product which contains a chloroalkyl group ortho to the alkyl substituent. In the embodiment wherein the aromatic compound is a benzene ring, the product corresponds to the for¬ mula ^•

wherein R is a hydrocarbyloxycarbonyl, carbox- amide, hydrocarbylcarbonyl, carboxylate, halocar- bonyl, nitrile, nitro, sulfone or sulfoxide group and R 1, R2 and c are defi.ned as her ^* ei.nbefore.

R is more preferably a halo carbonyl or hydro¬ carbyloxycarbonyl group, with hydrocarbyloxycarbonyl being the most preferred group. Preferably c is 0 or 1, most preferably 0.

In this process the chloroalkylating agent is preferably chloromethyl methyl ether, although other chloroalkylating agents such as bis- (chloromethyl) ether could be used. At least a 2:1 molar excess of the chloroalkylating agent to the alkyl-substituted aromatic compound is needed. It is pref rable to use between a 6:1 and 3:1 ratio of chloroalkylating agent to alkyl aromatic com- - pound. The catalyst is ferric chloride (FeCl_) while the cocatalyst is thionyl chloride. The

catalyst can be present in between 0.1 and 1.0 mole per mole of alkyl aromatic compound. ^* More preferably between 0.2 and 0.4 mole of catalyst are present for each .mole of alkyl aromatic compound. Preferably between 0.1 and 1.0 mole of thionyl chloride per mole of alkyl aromatic compound is used, more preferably between 0.2 and 0.4 mole per mole of alkyl aromatic compound.

This process can be performed at a tem- perature of between 40°C and 80°C, preferably

40°C and 60°C. Below 40°C, the reaction rate is low. The boiling point of some of the com¬ ponents of the reaction mixture starts at 80°C.

This process can be done by contacting the alkyl aromatic compound with the chloromethyl- ating agent, catalyst and cocatalyst in a suitable solvent. Suitable solvents include chlorinated hydrocarbon solvents. Thereafter the reaction mixture is heated to the appropriate temperature.

The product can be recovered by quench¬ ing the reaction mixture with alcohols or water to inactivate the chloroalkylating agents remaining, stripping off the volatiles and washing out the catalyst with water. The product thereafter is recovered by distillation.

The ortho chloroalkylated alkyl aromatic compounds can be converted to aromatic compounds with cyclobutene rings fused thereto, by pyrolysis. This is achieved by contacting the ortho chloroalkylated

alkyl aromatic compound with at least 2 times its weight of a suitable diluent, and thereafter pass¬ ing the mixture through a reactor at a temperature of 550°C or greater and a pressure of between at os- pheric and 25 mm of mercury. Suitable dilu¬ ents are generally substituted aromatic compounds which are inert to ^" the chloro ethylated alkyl aro¬ matic compound and are stable at pyrolysis temper¬ atures. Examples of suitable diluents are benzene, toluene, xylenes, chlorobenzenes, nitrobenzenes, methylbenzoates, phenyl acetate or diphenyl acetate. Preferred diluents are the xylenes. Preferable tem¬ peratures are between 700°C and 750°C. Pref¬ erable pressures are between 35 and 25 mm of mercury. In a preferred embodiment, the reaction mixture is passed through a hot tube packed with an inert material, for example, quartz chips or stainless steel helices. The product can be recov¬ ered by distillation. The product wherein the aro- matic compound is benzene corresponds to the formula

wherein R 1, R2, R11 and c are as hereinbefore defined.

In the preferred embodiment wherein R is a hydrocarbyloxycarbonyl moiety, the hydrocar¬ byloxycarbonyl moiety can be converted to a car¬ boxylate moiety by contacting the substituted (aryl- cyclobutene) compound with at least a molar equiva¬ lent of alkali metal hydroxide in an alkanol-water

solvent system. In the embodiment wherein the aro¬ matic radical is benzene, the product corresponds to the formula

tl

0

wherein R , R and c are as hereinbefore defined.

Thereafter the carboxylate-substituted (arylcyclobutene) compound can be converted to an acid chloride by contacting the carboxylate-substi- ^' tuted (arylcyclobutene) compound with thionyl chlo¬ ride and refluxing at 70°C to 80°C. The acid halide- -substituted (arylcyclobutene) so formed can be used to prepare the novel monomers of this invention, as described hereinafter. In the embodiment wherein the aryl radical is a benzene ring, the product cor¬ responds to the formula

wherein R 1, R2 and c are as hereinbefore defined.

In an alternative synthesis, an aryl compound with ortho dibromomethyl groups can be

re¬

converted to a 1,2-diiodoarylcyclobutene, by con¬ tacting the aryl compound substituted with ortho dibromomethyl moieties with an alkali metal iodide

, in an alkanol solvent at reflux so as to form the diiodoarylcyclobutenes. The product can be recov-

- ered by filtering, evaporating the filtrate and recrystallizing the product. In the embodiment wherein the aryl radical is a benzene radical, the starting material corresponds to the formula

wherein R and c are as hereinbefore defined and the iodobenzocyclobutene corresponds to the formula

wherein R and c are as hereinbefore defined.

The 1,2-diiodoarylcyclobutenes can be converted to de alogenated arylcyclobutenes by dis¬ solving the 1,2-diiodoarylcyclobutenes in an alco¬ hol solvent, preferably methanol or ethanol and contacting the solution with an alkali metal hydrox¬ ide in the presence of a palladium-on-carbon cata¬ lyst and H ₂ gas at a temperature of 20°C to 30°C. In general, at least between 2 and 4 moles of

alkali metal hydroxide per mole of 1,2-diiodoarylcyclo- butene is used. Preferably, between 50 and 200 psi (344) and 1379 kPa) of hydrogen gas is used. The aryl- cyclobutenes prepared in this manner can be recovered by distillation. In the embodiment wherein the aryl radical is a benzene radical, the product corresponds to the formula

wherein R and c are as. hereinbefore defined.

The arylcyclobutene is thereafter brominated.

In this process, the arylcyclobutene is dissolved in acetic acid and contacted with a brominating agent of pyridinium hydrobromide perbromide in the presence of mercuric salts, for example, mercuric acetate, at a temperature of between 20°C and 50°C. The brominated product can be recovered by extraction and distillation. In the embodiment wherein aryl radical is benzene, the product corresponds to the formula

wherein R and c are as hereinbefore defined.

The brominated arylcyclobutene can there¬ after be carbonylated to prepare a hydrocarbyloxy

carbonyl-substituted arylcyclobutene. This carbon- ylation is achieved by dissolving the brominated arylcyclobutene in an alkanol solvent, and there¬ after contacting the solution with carbon monoxide under pressure in the presence of a palladium cata¬ lyst, wherein the palladium is in the zero valence ^• state, in the further presence of an acid acceptor under conditions such that the brominated arylcyclo¬ butene compound undergoes carbonylation. Preferred catalysts are palladium acetate with a cocatalyst of triphenyl phosphine, palladium triphenyl phosphine tetrakis, and bis(triphenyl phosphine) palladium chloride complex. The acid acceptor is generally a tertiary amine. In general, the reaction vessel is pressurized with carbon monoxide to a pressure of between atmospheric and 3000 psi (20684 kPa), preferred pressures are between 600 and 1000 psi (4136 and 6895 kPa).

This process is preferably run at a tem- perature of between 100°C and 140°C, most preferably between 120°C and 130°C. The hydrocarbyloxycarbonyl arylcyclobutene can be recovered by filtering off the catalyst, washing away the acid scavenger with a 10 percent strong acid solution, stripping off the solvent and distilling the product to purify it. To prepare a carboxami e-substituted arylcy¬ clobutene, a primary or secondary amine is substi¬ tuted for the alcohol solvent. In the embodiment wherein the aryl radical is a benzene radical, the process corresponds to the following equation:

wherein R and c are as hereinbefore defined and

R 6 and R12 are hydrocarbyl moieties. The hydrocar- byloxycarbonyl-substituted or σarboxamide-substi- tuted arylcyclobutenes can thereafter be acidified and converted to acid chlorides by the process described hereinbefore.

In another preparation of an arylcyclo¬ butene, the reaction may follow that reported by Skorcz and Kaminski, Orq. Syn. , 48, pages 53-56 (1968). In a typical preparation, an alkyl cyano- acetate is added to a solution of sodium metal in ethanol followed by the addition of an ortho-halo- methylaryl halide. The alkyl 2-(0-halomethylaryl)- cyanoacetate is isolated and treated with aqueous sodium hydroxide. Subsequent acidification results in the cyanoacetic acid derivative. That deriva¬ tive is placed into N,N-dimethylformamide and is refluxed to form the 3-(0-halomethylaryl)propioni- trile derivative which is isolated and added to a suspension of sodamide in liquid ammonia. After an appropriate reaction time, ammonium nitrate is added and the ammonia allowed to evaporate. The cyanoarylcyclobutene is isolated by ether extrac¬ tion and purified by fractional distillation under reduced pressure.

Substituted arylcyclobutenes can be pre¬ pared by the same technique by using the appropri¬ ately substituted reactants, -such as an alkyl or alkoxybenzyl halide. Also substituents can result from using an alkyl haloacetate or a dialkylmalonate.

In another preparation based on the paper by Matsura et al., Bull. Chem. Soc. Jap., 39, 1342 (1966), o-aminoaryl carboxylic acid is dissolved in ethanol and hydrochloric acid added. Isoamylnitrite is slowly added to the cold-stirred solution and diethyl ether is then added. The product, aryldi- azonium-2-carboxylate hydrochloride, is filtered. That product is placed in a solvent, preferably ethylene dichloride, and acrylonitrile and propyl- ene oxide is added to the stirred mixture which is then heated under nitrogen until the reaction is complete. After cooling, the mixture is filtered and the product, 1-cyanoarylcyclobutene, is iso¬ lated by fractionally distilling the filtrate under reduced pressure.

Amounts of reactants, reaction parameters and other details can be found in the cited article, the examples of this application, or can be easily deduced therefrom.

In a next sequence ^" of reactions, the cyano- arylcyclobutene or .substituted derivative is nuclear substituted. In one preparation, the cyanoarylcyclo- butene is added slowly to a cold solution of sodium

nitrate in concentrated sulfuric acid to form 5-nitro- -1-cyanoarylcyclobutene. That nitiro compound is iso¬ lated, dissolved in ethanol and reduced by hydrogena- tion over a palladium on carbon catalyst. The iso¬ lated product is 5-amino-l-cyanoarylcyclobutene. In the preferred embodiment where the aryl radical is benzene, the product corresponds to the formula

wherein R 1 and R2 are as hereinbefore defined.

The formation of the arylcyclobutenyl amido alkenoic acid is achieved by reacting an unsat¬ urated cyclic anhydride with an amine-substituted arylcyclobutene. The cyclic anhydride corresponds to the formula

0

II

O

and the amine-substituted arylcyclobutene corre¬ sponds to the formula

wherein

Ar is an aromatic radical;

R is separately in each occurrence a hydrocarbyl, hydrocarbyloxy, hydrocarbylthio, an electron-donating or electron-withdrawing group; X is an alkenylene moiety which can be substituted with one or more hydrocarbyl, hydrocarbyloxy or hydrocarbylthio groups;

Y is a direct bond or a divalent organic radical; and a is an integer of between 0 and 3.

This process is exemplified by the following equation

^' 0

This reaction is exemplified in one preferred embodi¬ ment wherein the anhydride is aleic anhydride and the arylcyclobutene is 4-aminobenzocyclobutene, and is illustrated by the following equation:

wherein R in each occurrence is as hereinbefore defined.

The cyclic anhydride and amino-substi¬ tuted arylcyclobutene are contacted in a suitable solvent at a temperature of between -40°C and 100°C. Suitable solvents include aliphatic hydrocarbons, aromatic hydrocarbons, ethers and halogenated hydro¬ carbons. It is preferred to run the process under an inert atmosphere. It is also preferred to use freshly sublimed anhydride as any impurities in the anhydride can result in very poor yields. It is also preferred to use at least a 5 percent excess of anhydride so as to drive the reaction to comple¬ tion with respect to the amino-substituted arylcy¬ clobutene compound.

Preferred temperatures are between 0°C and 50°C with between 20°C and 25°C being most pre¬ ferred.

The N-arylcyclobutenyl amido alkenoic acid can be dehydrated by one of two methods. In the preferred embodiment, the N-arylcyclobutenyl amido alkenoic acid is contacted with a dehydrating

agent in an aprotic reaction medium in the presence of a nickel II salt catalyst. In general, the reac¬ tion medium is an aprotic solvent and can include ketones, ethers, amides or aliphatic halogenated hydrocarbons. Preferred reaction media include the ketones, with acetone being most preferred. The dehydrating agents include anhydrides, carbodiimides and isocyanates; with the anhydrides being preferred and acetic anhydride being most preferred.

The catalyst is any nickel II salt with nickel II acetate being most preferred. In general, between 1 and 5 _. percent of the catalyst is useful. It is preferable to run this process in the presence of an aprotic base such as a carbon- ate or tertiary amine, preferably a tertiary amine. In general, between 20 and 200 mole percent of a tertiary amine is used, with between 100 and 150 mole percent being preferred, wherein mole percentages are based on the starting N-aryl- cyclobutenyl amido alkenoic acid. The mole ratio of the dehydrating agent to the N-arylcyclobutenyl amido alkenoic acid is between 4:1 and 1:1, preferably between 1.5:1 and 1:1.

It is preferred to run this process under an inert atmosphere. Temperatures which are useful are those at which the dehydration takes place. Preferable temperatures are between -20°C and 100°C, with between 15°C and 25°C being most pre¬ ferred.

In this reaction, the N-arylcyclobutenyl amido alkenoic acid is often not soluble in the reaction medium but the cyclic imide product is. The reactant is slurried in the reaction media and exposed to the reaction conditions described. The completion of the reaction is noted by dissolution of the reactants indicating formation of products.

In an alternative procedure, the N-aryl¬ cyclobutenyl amido alkenoic acid can be dehydrated by dispersing the compound in a glacial acetic acid reaction media in the presence of an alkali or alka¬ line earth metal acetate salt, and heating the reac¬ tion mixture to a temperature at which the dehydra¬ tion takes place to form the cyclic imide rings. Generally, a sufficient amount of alkali or alka¬ line earth metal acetate salt to cause complete dehydration is suitable. Preferably, at least an equimolar amount of alkali or alkaline earth metal acetate salt is used, most preferably an excess of 5 mole percent. The process can be run at any tem¬ perature at which the dehydration takes place, pref¬ erable temperatures are between 50°C and 140°C, with between 100°C and 120°C being most preferred. Comple¬ tion of the reaction is indicated by dissolution of the product.

in both instances, the product can be recovered by washing with water and thereafter an aqueous solution of an inorganic base.

The precursor for the hydrocarbylene amino- • -bridged arylcyclobutenyl amido alkenoic acid can be prepared by the following procedure. An a ino-substi- tuted arylcyclobutene is- reacted with about, an equi- molar amount of a hydrocarbon substituted with alde¬ hyde and nitro moieties, in thejpresence of between 0.3 to 1.5 moles of sodium cyanoborohydride in a methanolic solvent at 20°C to 25°C. The product is nitrohydrocarbylamino-substituted arylcyclobutene. The process can be exemplified by the following equation

wherein R 4 i.s hydrocarbylene and R7 i.s hydrogen or a' hydrocarbyl moiety and R 1, R2 and Ar are as herein- before defined. The nitro moiety on the nitro- hydrocarbylamino-substituted arylcyclobutene is reduced to an amine moiety by contacting with an excess of metallic zinc in a concentrated hydrochlo¬ ric acid solution at between 20°C and reflux, or alternatively, by hydrogenation in ethonal over a palladium catalyst at about 25°C and 50 psi (344 kPa). The product corresponds to the formula

) ₂ ) ₂

wherein a, R ¹ , R ² , R ⁴ , R ⁷ and Ar are as hereinbefore defined. The aminohydrocarbyl amino-substituted arylcyclobutene is thereafter reacted with a cyclic anhydride to prepare a hydrocarbylene amino-bridged N-arylcyclobutenyl amido alkanoic acid. The conditions for this reaction are as described hereinbefore for the reaction of an amino-substituted arylcyclobutene and a cyclic anhydride. This reaction is exemplified by the following equation

ti O

wherein X, Ar, R 1, R2, R4, R7 and a are as described hereinbefore.

A hydrocarbylene-bridged arylcyclobutenyl amido alkenoic acid can be prepared by the following

procedure. A carboxy-substituted or carboxyhydro- carbyl-substituted arylcyclobutene is reduced to a hydroxyhydrocarbyl-substituted arylcyclobutene by reacting the starting material with a 3:1 molar excess of diborane, or 2:1 molar excess of lithium aluminum hydride, in an ether or cyclic ether solvent at between 0°C to 20°C. This process is exemplified by the following equation

HO

wherein R is a direct bond or a hydrocarbylene moiety and a, R 1, R2 and Ar are as defined herein¬ before.- The hydroxyhydrocarbyl-substituted arylcy- clobutene is reacted with a slight excess of thionyl chloride to prepare a chlorohydrocarbyl-substituted arylcyclobutene. The reactants are usually con¬ tacted neat or in a methylene chloride solvent at a temperature of between 0°C and 50°C. An example of the product corresponds to the formula

(R ¹⁾

Cl-CH ₂ -R ⁸ -Ar (C(R ² ) ₂ ) ₂

wherein a, R 1, R2, R8 and Ar are as hereinbefore defined.

The chlorohydrocarbyl-substituted arylcyclobutene is thereafter reacted with about an equimolar amount

of potassium phthalimide to prepare an N-arylcyclo- butenylhydrocarbyl phthalimide. The reactants are generally contacted neat at temperatures of between 100"C and 200°C. This reaction is exemplified by the following equation

wherein a, Ar, R 1, R2 and R8 are as hereinbefore defined. The N-arylcyclobutenylhydrocarbyl phthalamide is reacted with about one equivalent of hydrazine hydrate to prepare an aminohydrocarbyl-substituted benzocyclobutene. The reactants are contacted in an alkanol solvent at the reflux of the solvent. The product corresponds to the formula

wherein Ar, a, R 1, R2 and R8 are as hereinbefore defined. The aminohydrocarbyl-substituted benzo- cyclobutene is thereafter reacted with an unsatu-

rated cyclic anhydride to prepare an N-hydrocarbyl- arylcyclobutenyl amido alkenoic acid under the conditions described hereinbefore. This process is exemplified by the following equation

wherein a, X, Ar, R 1, R2, R3 and R8 are as hereinbefore def

An alternative process for preparing a propylene-bridged arylcyclobutenyl amido alkenoic acid is described by the following procedure. A hydroxymethyl-substituted arylcyclobutene is reacted with a six molar excess of chromium trioxide pyridine complex in methylene chloride solvent at 25°C to prepare an arylcyclobutene carboxaldehyde. The arylcyclobutene carboxaldehyde can thereafter be reacted with a molar equivalent of carboethoxy eth- ylene triphenyl phosphorane in tetrahydrofuran sol- vent at 0°C and then thereafter 60°C, to prepare ethyl-3-(arylcyclobutenyl)propenoate. The ethyl-3- -(arylcyclobutenyl)propenoate is thereafter reacted with excess hydrogen gas over a palladium metal cata¬ lyst of 2 weight percent on a support in an ethanol solvent at 25°C to prepare.ethyl-3-(arylcyclobutenyl)-

propanoate. The ethyl-3-(arylcyclobutenyl)propano- ate can thereafter be reacted with a 2 molar excess of lithium aluminum hydride in a tetrahydrofuran solvent at 65°C to prepare a 3-hydroxypropyl- arylcyclobutene. The 3-hydroxypropy1arylcyclobu¬ tene can thereafter be reacted with at least a 10 percent molar excess of thionyl bromide at 60°C to prepare 3-bromopropylarylcyclobutene. The 3-bromo- propylarylcyclobutene is thereafter reacted with a molar equivalent of sodium nitrite in N,N-dimethyl- forma ide solvent at 20°C to prepare 3-nitropropyl- arylcyclobutene. The 3-nitropropylarylcyclobutene is thereafter hydrogenated using excess hydrogen gas over a palladium metal catalyst in ethanol solvent at 25°C to prepare a 3-aminopropylarylcy¬ clobutene. The 3-aminopropylarylcyclobutene can thereafter be reacted with a molar equivalent of an anhydride as described hereinbefore to prepare the propylene-bridged arylcyclobutenyl amido alken- oic acid.

An alternative method for-preparing an ethylene-bridged arylcyclobutenyl amido alkenoic acid is described by the following procedure. A bromo-substituted arylcyclobutene is reacted with a molar excess of ethylene in the presence of a pal¬ ladium acetate catalyst, 0.05 mole is prefer¬ able, to prepare a vinyl-substituted arylcyclobu¬ tene. The vinyl-substituted arylcyclobutene is thereafter reacted with a molar equivalent of a borane tetrahydrofuran complex at 0°C followed by addition of hydrogen peroxide and sodium hydroxide to prepare a 2-hydroxyethylarylcyclόbutene. The

2-hydroxyethylarylcyclobutene is thereafter reacted with- at least a 10 percent molar excess of thionyl chloride at 70°C to prepare a 2-chloroethylarylcy¬ clobutene. The 2-chloroethylarylcyclobutene is thereafter reacted with a 10 percent molar excess of potassium phthalimide in the presence of about 0.6 mole of potassium carbonate at 150°C-200°C to prepare a compound which corresponds to the formula

wherein Ar, a, R 1 and R2 are as hereinbefore defined. Such compound is thereafter reacted with a 10 percent molar excess of hydrazine hydrate to prepare 2-aminoethylarylcyclobutene. The 2-amino- ethylarylcyclobutene can thereafter be reacted with a cyclic anhydride to prepare the ethylene-bridged arylcyclobutenyl amido alkenoic acid as described hereinbefore. An alternative procedure for prepar- ing a 2-aminoethylarylcyclobutene involves reacting a vinyl-substituted arylcyclobutene with 1 mole of a borane tetrahydrofuran complex in tetrahydrofuran at 0°C .and thereafter contacting the reaction prod¬ uct with 2 equivalents of hydroxylamine-O-sulfonic acid to prepare the 2-aminoethylarylcyclobutene.

To prepare a mercaptoarylcyclobutene, an arylcyclobutene sulfonic acid and equimolar amounts

of sodium hydroxide are contacted in aqueous solution at 20°C-25°C to prepare sodium arylcyclobutene sulfonate. The sodium arylcyclobutene sulfonate is dried at 100°C, and thereafter contacted in neat form with 0.48 mole of phosphorous pentachloride at 170°C to 180°C to prepare an arylcyclobutene sulfonyl chloride. The arylcyclo¬ butene sulfonyl chloride is reduced with zinc, 4.9 moles, in the presence of 6.8 moles of concentrated sulfuric acid at 0°C to prepare the mercaptoaryl- cyclobutene.

To prepare the alkylenethio-bridged aryl¬ cyclobutenyl amido alkenoic acid, equimolar amounts of a mercaptoarylcyclobutene, sodium hydroxide and a dihaloalkane are contacted in an alkanol solvent at between 0°C and 50°C. The product is a haloalkyl- substituted arylcyclobutenyl sulfide. This reaction is exemplified by the following equation

HS-A:ζ__ c(R ² ) ₂ ) ₂ + NaOH + R ⁴ ^→ X-R ⁴ -S-Ar (C(R ² ) ₂ ) ₂ + HX

wherein X is halogen, R 4 is a divalent alkane radical and Ar, a, R 1 and R2 are as hereinbefore defined. Two moles of the haloalkyl-substituted arylcyclobutenyl sulfide is contacted with 0.8 moles of potassium phthalimide and 0.4 mole of potassium carbonate. The reactants are contacted neat at a temperature of 190°C to prepare an n-phthalimidoalkylarylcyclobutenyl

sulfide. This process is exemplified by the following equation

0

wherein X, Ar, a, R 1, R2 and R4 are as hereinbefore defined.

The phthalimidoalkylarylcyclobutenyl sul¬ fide is contacted with a hydrazine hydrate in a mole ratio of 1 to 1.25, respectively, in an alkanol solvent at reflux to prepare an aminoalkyl arylcyclo¬ butenyl sulfide. In one preferred embodiment, the product corresponds to the formula

(R ¹ )

H ₂ N-R ⁴ -S-Ai [ C(R ² ) ₂ ) ₂

wherein Ar, a, R 1, R2 and R4 are as hereinbefore defined.

The aminoalkylarylcyclobutenyl sulfide is then reacted with a cyclic anhydride to prepare a thioalkylene-bridged N-arylcyclobutenyl amido alkenoic acid. This is achieved under conditions described hereinbefore.

The thiopropylene-bridged arylcyclobu¬ tenyl amido alkenoic acid can alternatively be pre¬ pared by the following process. One mole of mer- captoarylcyclobutene is reacted with 1 mole of ethylacrylate in toluene at 25°C to pre¬ pare 2-(carboethoxy)ethylsulfide-substituted aryl¬ cyclobutene. The 2-(carboethoxy)ethylsulfide-sub¬ stituted arylcyclobutene is thereafter contacted with 2 moles of lithium'aluminum hydride in tetra- hydrofuran at 65°C to prepare a 3-hydroxypro- pylsulfidearylcyclobutene. The 3-hydroxypropy1sul¬ fidearylcyclobutene is thereafter reacted with 1 mole of p-toluene sulfonyl chloride in the presence of 1 mole of a trialkyla ine in methylene chloride solvent at 0°C then at 20°C to prepare toluene sul¬ fonate propylsulfidearylcyclobutene, which product corresponds to the formula

wherein Ar, a, R 1 and R2 are as hereinbefore defined. This compound is thereafter reacted with a 10 mole percent excess of potassium phthal¬ imide in the presence of 0.6 mole of potassium

carbonate at 140°C to prepare a phthalimide derivative, which corresponds to the formula

(R ) 2)2

wherein Ar, a, R 1 and R2 are as hereinbefore defined.

This product can thereafter be reacted with 1 mole of hydrazine hydrate at 100°C to prepare 3-aminopropylthio- -substituted arylcyclobutene _, .

An alternative method for preparing a 2-amino- ethylthioarylcyclobutene involves contacting a mercapto- -substituted arylcyclobutene with 1 mole of thyleneamine.

To prepare arylenethio-bridged N-arylcy¬ clobutenyl cyclic imide, equimolar amounts of a mer- captoarylcyclobutene, sodium hydroxide and a halo- nitro-substituted aromatic compound are contacted in an alkanol solvent under reflux to prepare a nitroaryl arylcyclobutenyl sulfide. The nitro group on the nitroaryl arylcyclobutenyl sulfide is reduced by contacting one mole of such compound with two moles of tin and six moles of concentrated hydrochloric acid to prepare an aminoaryl arylcyclobutenyl ^' sulfide. The aminoaryl arylcyclobutenyl sulfide is thereafter contacted with a cyclic anhydride in equimolar amounts in methylene chloride at a temperature of 0°C to 25°C to prepare an arylenethio-bridged N-arylcyclobutenyl

amido alkenoic acid. The arylenethio-bridged N-arylcyclobutenyl amido alkenoic acid is dehydrated using procedures described hereinbefore to prepare an arylenethio-bridged N-arylcyclobutenyl cyclic imide.

The hydrocarbylenethio-bridged N-arylcyclo¬ butenyl cyclic imides can be contacted with equimolar amounts of peracetic acid in an ethyl acetate solvent at between 0°C to 20°C to prepare a hydrocarbylene- sulfinyl-bridged N-arylcyclobutenyl cyclic imide. The hydrocarbylenethio-bridged N-arylcyclobutenyl cyclic imide can be contacted with 2 moles of peracetic acid for each mole of the bridged -cyclic imide in ethyl ace¬ tate solvent at 0°C to 20°C to prepare a hydrocarbylene¬ sulfonyl-bridged N-arylcyclobutenyl cyclic imide.

The hydrocarbyleneamido-bridged arylcyclo¬ butenyl amido alkenoic acids can be prepared by the following procedures. In the first step, a compound substituted with both a nitro group and acid chloride moiety is reacted with an aminoarylcyclobutene in the presence of 1 equivalent of a trialkylamine, in.a chlorinated hydrocarbon solvent at 0°C and thereafter at 20°C to prepare a nitrohydrocarbyleneamido-substituted arylcyclobutene. This reaction can be illustrated by the following equation

wherein Ar, a, R 1, R and R8 are as previously defined,

Q and R is an alkyl group. The nitro group is thereafter reduced to an amino group by contacting the compound prepared in the previous reaction with hydrogen gas in excess in the presence of a palladium metal cata¬ lyst in an alkanol solvent at about 25°C. This prod¬ uct is an aminohydrocarbyleneamido-substituted aryl¬ cyclobutene which corresponds to the formula

wherein Ar, a, R 1, R2 and R8 are as hereinbefore defined.

This aminohydrocarbyleneamido-substituted arylcyclo- butene can thereafter be reacted with an unsaturated cyclic anhydride to prepare a hydrocarbylenea ido-

-bridged arylcyclobutenyl amido alkenoic acid, using the procedure described hereinbefore, .as illustrated by the following equation

wherein X, Ar, a, R 1, R2 and R8 are as hereinbefore defined.

In one preferred embodiment, this process involves reacting a nitroaroyl chloride with the amino¬ arylcyclobutene to prepare a nitroarylamidoarylcyclo¬ butene which can thereafter be hydrogenated to the aminoarylamidoarylcyclobutene, which is thereafter reacted with the unsaturated cyclic anhydride as described hereinbefore.

Alternatively, the alkyleneamido-bridged arylcyclobutenyl amido alkenoic acids can be prepared by the following process. In the first step, 1 mole of a cyclic lactone is reacted with an amino-substi¬ tuted arylcyclobutene in toluene at 100°C to

prepare a hydroxy alkyleneamido-substituted arylcy¬ clobutene. This process is described by the follow¬ ing equation

wherein Ar, a, R 1 and R2 are as hereinbefore defined and x is 3 or greater. The hydroxyalkylamide- arylcyclobutene is thereafter reacted with a 10 per¬ cent mole excess of thionyl chloride at 70°C to prepare a chloroalkylamide-substituted arylcyclo¬ butene as described by the following equation

wherein Ar, a, x, R 1 and R2 are as hereinbefore defined.

The chloroalkylamido-substituted arylcyclobutene is reacted with a 2 molar excess of sodium iodide in methanol at reflux to prepare a gamma-iodoalkylamido- arylcyclobutene. The gamma-iodoalkylamidoarylcyclo- butene is thereafter reacted with a 10 percent mole excess of sodium nitrite in N,N-dimethylformamide solvent at 25°C to prepare a gamma-nitroalkylamido-

arylcyclobutene. The gamma-nitroalkylamidoarylcy- clobutene is thereafter hydrogenated with excess hydro¬ gen over a ^"" palladium metal catalyst in an ethanol solvent at 20°C-25°C to prepare a gamma-amino- alkylamidoarylcyclobutene derivative. This gamma- -aminoalkylamidoarylcyclobutene derivative-can there¬ after be reacted with an unsaturated cyclic anhydride under conditions described hereinbefore to prepare the alkyleneamido-bridged arylcyclobutenyl amido alkenoic acid. In preferred embodiments, the initial lactone is butyrolactone which prepares the propyl- eneamido-bridged species, a valerolactone starting material results in the preparation of the butylene- amido-bridged species, and the caprolactone start- ing material results in the pentyleneamido-bridged species.

The methyleneamido-bridged arylcyclobu¬ tenyl amido alkenoic acid can alternatively be pre¬ pared by the following sequence. Chloroacetyl chlo- ride is reacted with an amino-substituted arylcyclo¬ butene in the presence of a trialkylamine in ethyl- ene chloride at 0°C, then 20°C to prepare an alpha- -chloroaceta ide-substituted arylcyclobutene. The alpha-chloroacetamidearylcyclobutene is thereafter reacted with a 2 molar excess of sodium iodide in methanol at reflux to prepare the iodoacetamidearyl- cyclobutene. The iodoacetamidearylcyclobutene can be converted to an aminoacetamide derivative, and thereafter to a methyleneamido-bridged arylcyclobu- tenyl amido alkenoic acid by the sequence of reac¬ tions described in the previous paragraph. ¹

An alternative method for the preparation of an ethylene mido-bridged arylcyclobutenyl amido alkenoic acid involves the following reaction sequence. One mole of acryloyl chloride is reacted with 1 mole of an amino-substituted arylcyclobutene in the pres¬ ence of 1 mole of a trialkylamine, in a ethylene chloride solvent at ^" 0°C, then at 20°C to prepare an acrylamide-substituted arylcyclobutene. Thereafter acrylamidearylcyclobutene is reacted with excess ammonia in ethanol at 20°C to prepare a beta-amino- propionamidearylcyclobutene, which can thereafter be reacted with a cyclic unsaturated anhydride to prepare the ethylenea ido-bridged arylcyclobutenyl amido alkenoic acid.

An alkyleneoxy-bridged arylcyclobutenyl amido alkenoic acid can be prepared by the follow¬ ing sequence of reactions. A hydroxyarylcyclobu- tene is reacted with an alkyl group substituted with a bromo and chloro group in the presence of a molar equivalent of sodium hydroxide in ethanol at reflux to prepare a chloroalkyl ether of an arylcyclobutene. This reaction can be illustrated by the following reaction sequence wherein R is an alkylene group and Ar, a, R 1 and R2 are as hereinbefore defined.

) ₂ ) ₂

+ HBr

The chloroalkyl ether of the arylcyclobutene is thereafter reacted with a 2 molar excess of sodium

iodide in methanol at reflux to prepare an iodoal- kyl ether of the arylcyclobutene, which is thereaf¬ ter reacted with sodium nitrite, a molar equivalent thereof, in N,N-dimethylformamide solvent at 25°C to prepare a nitroalkyl ether of arylcyclobutene. The nitroalkyl ether of arylcyclobutene can be reduced with excess hydrogen over a palladium metal catalyst in an ethanol solvent at 25°C to prepare an aminoalkyl ether of an arylcyclobutene. Such aminoalkyl ether of arylcyclobutene can thereafter be reacted with an unsaturated cyclic anhydride, under conditions described hereinbefore to prepare the alkyleneoxy-bridged arylcyclobutenyl amido alkenoic acids, as illustrated by the following equation

(R ² ) ₂ ) ₂ .

II

0

0

wherein X, Ar, a, R , R and R are as hereinbefore defined.

An aryleneoxy-, or alkaryleneoxy-bridged arylcyclobutenyl amido alkenoic acid can be prepared by the following sequence of reactions. An aromatic compound or alkyl-substituted aromatic compound sub- stituted with a nitro group and a chloro group is reacted with a hydroxy-substituted arylcyclobutene in the presence of 2 equivalents o ^' f potassium car¬ bonate in an N,N-dimethylformamide solvent to pre¬ pare a nitroaryl ether or nitroalkaryl ether of an arylcyclobutene. The nitroaryl ether, or nitro¬ alkaryl ether of the arylcyclobutene can there¬ after be contacted with two moles of tin and six moles of hydrochloric acid to reduce the nitro group to an amino group so as to prepare an amino- aryl ether or an aminoalkaryl ether of an arylcy¬ clobutene. Alternatively, the nitro group may be reduced to an amino group by hydrogenation over a palladium metal catalyst in methanol or ethanol at 25°C and 50 psi (344 kPa) . Such compounds are thereafter reacted with cyclic unsaturated anhy¬ drides as described hereinbefore to prepare the aryl ether-, or alkaryl ether-bridged arylcyclobu¬ tenyl amido alkenoic acids.

Hydrocarbylenecarbonyloxy-bridged aryl- cyclobutenyl amido alkenoic acids may be prepared by the following procedure. A hydrocarbon contain¬ ing nitro and acid chloride moieties is reacted with 1 mole of a hydroxy-substituted arylcyclobutene in the presence of 1 mole of a trialkylamine in methyl- ene chloride solvent at 0°C and thereafter at 20°C to prepare a nitrohydrocarbylenecarbonyloxy-substi¬ tuted arylcyclobutene. This reaction is illustrated by the following equation

N0 ₂ -R ) ₂ ) ₂

wherein Ar, a, R 1, R and R8 are as hereinbefore defined. Thereafter the nitrohydrocarbylenecarbonyloxy-sub- stituted arylcyclobutene is contacted with hydrogen gas in excess to hydrogenate the nitro group, and with 1 mole of hydrochloric acid in an ethanol sol¬ vent at 25°C to prepare an ammonium chloride salt-substituted hydrocarbylenecarbonyloxy-substi- tuted arylcyclobutene as illustrated by the follow¬ ing equation

Pd Cat

wherein Ar, a, R 1, R2 and R8 are as hereinbefore defined. The ammonium chloride salt is thereafter reacted with an unsaturated cyclic anhyride in the presence of a trialkylamine as described hereinbefore to prepare a hydrocarbylenecarbonyloxy-bridged aryl¬ cyclobutenyl amido alkenoic acid.

Hydrocarbyleneoxycarbonyl-bridged aryl¬ cyclobutenyl amido alkenoic acids can be prepared by the following process. A hydrocarbon containing

a hydroxy and nitro _. group is reacted with 1 mole of an acid chloride-substituted arylcyclobutene in the presence of a molar equivalent of a tri-alkylamine in methylene chloride solvent at 0°C, then at 20°C to prepare a nitrohydrocarbyleneoxycarbonyl-substituted arylcyclobutene. This reaction is exemplified by the following equation

N0 ₂ -R—OH ) ₂ ) ₂ IiLi ->

) ₂

wherein Ar, a, R 1, R2 and R8 are as hereinbefore defined, The nitrohydrocarbyleneoxycarbonyl-substituted aryl¬ cyclobutene is reacted with excess hydrogen and 1 mole of hydrochloric acid over a palladium catalyst in an ethanol solvent at 25°C to prepare an ammonium hydrochloride salt of a hydrocarbyleneoxy- carbonylarylcyclobutene. This process is exempli¬ fied by the following equation

) ₂ ) ₂

wherein Ar, a, R1, R2 and R8 are as hereinbefore defined.

The ammonium hydrochloride salt can thereafter be reacted with an unsaturated cyclic anhydride as described hereinbefore to prepare a hydrocarbylene- oxycarbonyl-bridged arylcyclobutenyl amido alkenoic acid. This process is exemplified by the following equation

0

II

0

wherein X, Ar, a, R 1, R and R 8 are as hereinbefore defined

The compounds of this invention are unique in several respects. They have a latent intramolecular diene and dienophile functionality. They are thermally stable for long periods at ele¬ vated temperatures, up to 100°C. They are readily polymerizable. The compounds of this invention are

useful in the preparation of polyimides by ho opo- lymerization of the compounds of this invention. It is believed that the polymerization takes place by a Diels-Alder reaction wherein the unsaturation on the amido alkenoic acid acts a dienophile while the - cyclobutene ring forms a diene which- reacts with the dienophile to form the polymeric compositions. ^' The compounds of this invention, when heated to polymeriza- - tion temperature, lose a molecule of water and the amido alkenoic acid portion of the molecule cyclizes to an imido functionality.

The polymers of this invention are"prepared by heating the compounds described hereinbefore to a temperature of at least 170°C. Preferable temperatures for polymerization are 200°C In general, it is preferable to run the polymerization at a temperature of between 170°C and 300°C, with between 200°C and 300°C being most preferred.

Wherein the arylcyclobutenyl amido alkenoic acid or a salt thereof corresponds to the formula

II

0

' ^* wherein Ar, R 1, R2, R3, X, Y, Z and a are as described hereinbefore; it is believed that the polymeric com-

position contains units which correspond to the for¬ mula

wherein Ar, R 1, R2, R3, X, Y and a are as described hereinbefore.

It is further believed that in one pre¬ ferred embodiment the polymers derived from mono¬ mers of such a formula result in the preparation of polymers which correspond generally to the for¬ mula

) ₂ )

wherein Ar, R 1, R2, R3, Y, Z and a are as described hereinbefore and d is a real number of at least 2 and most preferably at least 20.

In another preferred embodiment, the poly¬ meric composition is the homopolymer of a compound which corresponds to the formula

O

) ₂

).

wherein R 1, R2, R3, Y, Z and a are as hereinbefore defined. In this embodiment, it is believed that the polymer prepared contains units which corre¬ spond to the formula

wherein R 1, R2, R3, Y, Z and a are as hereinbefore defined.

In one preferred embodiment wherein the compound polymerized corresponds to said formula, it is believed that the polymer prepared corre¬ sponds to the formula

wherein R , R , R , Y, Z and a are as hereinbefore defined, and d is a real number of at least 2, pre¬ ferably at least 20.

The novel arylcyclobutenyl amido alkenoic acids of this invention are useful in the preparation of polymeric compositions. In general, these poly¬ meric compositions are prepared by contacting these arylcyclobutenyl amido alkenoic acids and heating them to the polymerization temperature of the par¬ ticular monomer used. The polymerization is an addition polymerization. Furthermore, no catalyst initiator or curing agents are necessary for the polymerization to take place. It is believed that the polymerization takes place when the cyclobutene ring undergoes transformation to prepare an aryl radical with two olefinic unsaturated moieties ortho to one another wherein the olefinic unsaturated moi¬ eties thereafter undergo reaction with the unsatu- ration in the amido alkenoic acid. It is to be noted that the temperature at which polymerization is initiated is dependent upon the nature of sub¬ stituents on the cyclobutene ring. In general,

wherein the cyclobutene ring is unsubstituted, the polymerization is initiated at 175°C. Wherein the cyclobutene ring is substituted with an electron-donating substituent, the polymeriza- _ tion temperature is generally lower, the higher the ability of the substituent to donate electrons, the lower the polymerization initiation temperature is.

The novel "compounds of this invention can be used to prepare coatings. The compounds are dis¬ solved in an aqueous solution, which is thereafter coated onto a substrate. The water is evaporated from the substrate leaving a coating of the novel compounds. Thereafter, the coated substrate ^' is exposed to temperatures at which the novel com¬ pounds of this invention undergo polymerization over a period of time for the polymerization to go to the desired degree of polymerization, resulting in a thermoset polymer coating on the substrate.

Under preferable conditions, temperatures of above 200°C for between 1 and 5 hours are used. It is preferable to .saturate the aqueous solution with the monomer, a 5 to 40 weight percent concen¬ tration of the monomer in the solvent is preferred.

The method of polymerization of the aryl¬ cyclobutenyl amido alkenoic acids has a significant effect on the nature and properties of the polymeric composition prepared. In one embodiment, the aryl¬ cyclobutenyl amido alkenoic acids of this invention can be melt polymerized. The melt polymerization

of arylcyclobutenyl amido alkenoic acids allows their use in the preparation of solid parts, as coatings, in composites, as adhesives and as fibers.

In one embodiment of the melt polymeri¬ zation, the monomer is heated to the temperature at which it melts, preferably this is a temperature of between 80°C and 100°C, and thereafter poured or injected into a mold. Thereafter, pressure is applied on the melted monomer in the mold. Gener¬ ally, pressures of between 100 and 2000 psi (689 and 13790 kPa) are suitable. Thereafter, the monomer is heated to a temperature at which the monomers undergo polymerization. This is preferably a temperature of between 200°C and 300°C, more preferably between 200°C and 250°C for between 10 minutes and 3 hours. Upon cooling, the polymerized composition can be removed from the mold.

Polymers prepared in this manner can sub- sequently be thermally treated at temperatures above 200°C to raise the modulus and lower the coefficient of expansion _. of such polymeric compositions.

In general, the polymers prepared by this method are insoluble in that they swell but do- not dissolve, are thermally stable at 200°C, have a good modulus, a low water pickup and are reasonably hard.

In another embodiment, the compounds of this invention can be used to prepare coatings and films. In such embodiments, the monomers are dis- solved in a suitable solvent and coated onto the

substrate of choice, and thereafter the coated sub¬ strate is exposed to temperatures at which the mono¬ mers undergo polymerization over a period of time sufficient for the polymerization to go to comple- tion. Under preferable conditions, temperatures of above 200°C for between 1 and 5 hours are used. Suitable solvents are those which volatil¬ ize away at temperatures below the polymerization temperature. Preferred solvents are cyclic and ali- phatic ethers, lower alkanols, amides, and chlori- . nated hydrocarbon solvents. It is preferable to saturate the solvent with the monomer, a 20 to 30 weight percent concentration of monomer in the sol¬ vent is preferred.

The arylcyclobutenyl amido alkenoic acids may be combined with -the powder-form or ^: fibrous fill¬ ers or reinforcing materials either before.or after heat treatment. For example, it is possible to impregnate powder-form or fibrous fillers, or rein- forcing materials such as quartz sand or glass cloths, with the arylcyclobutenyl amido alkenoic acids, optionally in solution.

Suitable fillers and reinforcing materi¬ als are, generally, in any powder form and/or fibrous products, for example, of the type commonly used in the production of moldings based on unsatu¬ rated polyester resins or epoxide resins. Examples of products such as these are, primarily, granular fillers such as quartz powder, ground shale, asbes- tos powder, powdered corundum, chalk, iron powder,; aluminum powder, sand, gravel and other fillers o-f

this kind, also inorganic or organic fibers, more especially glass fibers in the usual textile forms of fibers, filaments rovings, yarns, nonwovens, mats and cloths, etc. In this connection, amino silane- -based finishes have proven to be particularly effec¬ tive. It is also possible to use corresponding tex¬ tile structures of organic, preferably synthetic fibers (polyamides, polyesters) or on the basis of quartz, carbon, metals, etc., as well as onocrys- tals (whiskers).

The end products combined with fillers or reinforcing materials may be used in particular in vessel and pipe construction by the winding tech¬ nique, in electrical engineering, in mold construc- tion and tool making and also in the construction of heavily stressed components, in the lightweight construction of vehicles in aeronautical and astro- nautical engineering.

In another embodiment, the arylcyclobu- tenyl amido alkenoic acids can be used as adhesives. In such embodiment, one of the substrates to be joined is contacted with some form of the monomers, for example, the monomer in a powdered form. There¬ after, the second substrate to be adhesivated is contacted, with the substrate previously contacted with the monomer. Thereafter, pressure of at least 1 psi (6.9 kPa) is applied and the monomers and sub¬ strates are raised to a temperature at which the monomer undergoes polymerization.

In one embodiment, the arylcyclobutenyl amido alkenoic acids can be formed into a prepoly- mer which thereafter can be polymerized. To form the prepolymer, the arylcyclobutenyl amido alkenoic acids are contacted in an inert atmosphere or under vacuum and heated to a stage at which the polymeri¬ zation mixture is sufficiently viscous enough to be moldable in conventional molding equipment. In gen¬ eral, the monomers can be contacted at a "temperature of 190°C to 220°C for between 1 and 10 minutes.

Thereafter, the prepolymer can be used in various techniques to prepare the polymeric compositions of this invention. In one preferred embodiment, the prepolymer is cooled to form a powder which can be used to form compression molded articles, as an adhe¬ sive, and in many other uses. In another embodiment, a prepolymer of the arylcyclobutenyl amido alkenoic acids can be prepared by precipitation polymeriza¬ tion. In particular, the technique involves heat- ing such monomers in a solvent to prepare a lo ^' w molecular weight prepolymer that contains unreacted arylcyclobutene rings. A solvent is ^" used which dis¬ solves the monomer but not the prepolymer. As the prepolymer forms, it precipitates and is removed. The prepolymer can be fabricated in a hot compres¬ sion mold which reacts out the remaining arylcyclo¬ butene rings to give a thermoset polymer.

Preferable solvents are nonpolar solvents, such as aromatic hydrocarbons, aliphatic hydrocarbons, aliphatic chlorinated hydrocarbons, aromatic chlori¬ nated hydrocarbon solvents, biphenols, naphthalenes

or polychlorinated biphenols. The polymerization can take place at temperatures generally of between 200°C and 240°C for periods of between 1 and 5 hours.. In general, the monomer can be dissolved up to saturation in the solvent used. A 20 to 30 percent by weight solution of the monomer in the solvent is pre¬ ferred.

In another embodiment, the arylcyclobu¬ tenyl amido alkenoic acids can be polymerized by solution polymerization techniques. In this embodi¬ ment, the monomers are dissolved in dipolar aprotic solvents with boiling points above the polymeriza¬ tion temperature of the monomers. It is preferable that the solvents have a boiling point of above 200°C and more preferable that the solvents have a boiling point of above 250°C. Examples of preferred dipolar aprotic solvents include amides and sulfones. It is necessary to add to the solution lithium salts which solubilize the monomer in the solvents, preferably between 5 and 20 weight percent based on the monomer. A preferred lithium salt is lithium chlo¬ ride. The polymerization takes place by heating the polymerization solution to a temperature' at which the monomer undergoes polymerization, preferably above 200°C. The polymerization time is generally between 1 and 10 hours. The polymer can be recovered by adding water to precipitate the poly¬ mer from the reaction solution and thereafter strip¬ ping off the solvent. The polymers prepared with this method can be used in compression moldings or to prepare coatings. It is often desirable to pro¬ cess these polymers under elevated temperatures.

In another embodiment, the monomers of this invention which undergo polymerization at a temperature which is below the melting point of the monomer can be polymerized in a solid state polymer¬ ization. In this method, the monomer is heated to a temperature at which polymerization takes place. Polymers prepared in this method can be useful in the preparation of bearings, seals and other parts by powder metallurgy techniques.

The following examples are included to illustrate the invention, and do not limit the scope of the invention or the claims. Unless otherwise specified, all parts and percentages are by weight.

Example 1

(a) Preparation of Ethyl

2-(o-Chlorobenzyl) Cyanoacetate

Into a 3-liter, three-necked flask equipped with a mechanical stirrer, reflux condenser, addition funnel and nitrogen inlet was placed a solution of 35.64 c (1.55 moles) of sodium metal in 1050 mm of absolute ethanol. The solution was stirred under nitrogen and cooled to 0°C in an ice bath and 763.56 g (6,75 moles) of ethyl cyanoacetate was added dropwise over a period of 15 minutes. To this white suspension was added 241.56 g (1.5 moles) of o-chlorobenzyl chloride dropwise over 1 hour. After the addition was complete, the ice bath was removed and the mixture was slowly heated under nitrogen

to reflux and held there for 3 hours. The result¬ ing pink-colored mixture was allowed to cool under nitrogen overnight at room temperature. About 1 liter of ethanol was distilled from the reaction mixture and 1.5 liters of water were added. The organic layer was taken up in three 400-ml portions of methylene chloride, and the solutions were com¬ bined and washed once with 150 ml of water. The methylene chloride solution was dried over anhydrous magnesium sulfate, filtered and evaporated on a rotary evaporator. The residual liquid was dis¬ tilled under reduced pressure through an insulated 12-inch (30.5 cm) Vigreux column. A forerun of ethyl cyanoacetate (boiling point 55°C-60°C/0.3 mm Hg) came over first followed by pure ethyl 2-(o-chloroben- zyl)cyanoacetate. The infrared, Η and 13C nuclear magnetic resonance were used to establish the struc¬ ture. The yield was 68 percent of product having a boiling point of 130°C-135°C/0.3 mm Hg.

(b) Preparation of 2-(o-Chloro- benzyl)Cyanoacetic Acid

In a 2-liter, three-necked flask equipped with a mechanical stirrer, addition funnel and nitro¬ gen inlet was placed 243 g (1.02 moles) of ethyl 2-(o- -chlorobenzyl)cyanoacetate. A solution of 54.52 g

(1.363 moles) of sodium hydroxide pellets and 545 ml of water was added over a period of 15 minutes while stirring under nitrogen. Initially, the solution turned cloudy and then became clear. The resulting mixture was stirred for 5 hours at room temperature

under nitrogen. Water (445 ml) was added and the mixture was cooled in an ice bath. Acidifying to pH 1 with 4 N hydrochloric acid gave a fine white precipitate that was filtered and washed with water until neutral to litmus. The product was dried in a vacuum oven at 60°C overnight to yield 20 g (97 percent) of white powder. This material was recrys- tallized from toluene to give pure white crystals of 2-(o-chlorobenzyl)cyanoacetic acid identified by infrared, Η and 13C nuclear magnetic resonance.

The yield was 94 percent of product having a melting point of 132°C-134°C.

(c) Preparation of o-Chlorocinnamonitrile Into a 1-liter, three-necked flask equipped with a mechanical stirrer, reflux con¬ denser and nitrogen inlet was placed 138.5 g (0.66 mole) of 2-(o-chlorobenzyl)cyanoacetic acid and 220 ml of dry N,N-dimethylformamide. The mixture was stirred and slowly heated under nitrogen to reflux and held there for 6 hours. The resulting yellow mixture was allowed to cool under nitrogen overnight at room temperature. A precipitate (approximately 0.5 g) that formed was filtered off and the filtrate was poured into 1 liter of water. The organic layer was taken up in three 330-ml por¬ tions of ethyl ether/hexane (1:1 v/v), and the solutions were combined and washed once with 150 ml of water. The ethyl ether/hexane solution was dried over anhydrous magnesium sulfate, filtered and evap- orated on a rotary evaporator. The residual liquid

was distilled under reduced pressure through an insu¬ lated 12-inch (30.5 cm) Vigreux column with the product being collected at 82°C-85°C/0.3 mm Hg as a colorless liquid identified by infrared, Η and 13C nuclear mag- netic resonance. The yield was 94.7 percent.

(d) Preparation of 1-Cyanobenzocyclobutene

A 3-liter, three-necked flask equipped with a dry ice condenser, mechanical stirrer and

Claisen adapter fitted with an ammonia gas inlet and nitrogen inlet was rinsed with acetone, dried in an oven at 125°C, and heated with an air gun while flushing with nitrogen. The apparatus was cooled in a dry ice-acetone bath and the condenser was filled with a dry ice-acetone mixture. Ammonia gas flow was initiated and 600 ml was condensed out. The ammonia inlet tube was replaced by a stopper, and 0.4 g of powdered iron (III) nitrate was added. Sodium metal, 51.52 g (2.24 moles) was added in small portions over 1 hour. After all the sodium was added, the dry ice bath was removed and _i cooling was left to the dry ice condenser. Complete conversion of the sodium/ammonia solution to sodamide was indicated by a color change from deep blue to gray. Next, 92.82 g (0.56 mole) of o-chlorocinnamonitrile was added over a period of 10 minutes. The last traces of the nitrile were washed into the flask with small amounts of anhydrous ethyl ether. The dark green reaction mixture was stirred vigorously for 3 hours and then was treated with 134.4 g (1.68 moles ^' ) of solid ammonium nitrate. The ammonia was

allowed to evaporate overnight at roo ^" temperature. Water (420 ml) was cautiously added to the residue. The organic layer was taken up in two 224-ml por¬ tions of chloroform, and the solutions were combined and washed twice with 140 ml of aqueous 5 percent hydrochloric acid and _^ once with 140 ml of water. The chloroform solution was dried over anhydrous magnesium sulfate, filtered, and evaporated on a rotary evaporator. The residual liquid was dis- tilled under reduced pressure through an insulated 12-inch (30.5 cm) Vigreux column. The product was collected at 59°C-6-9°C/0.2 mm Hg. The infrared, 'H and 13C nuclear magnetic resonance were run t identify the product. The yield was 50 percent.

(e) Preparation of 5-nitro-

-1-cyanobenzocyclobutene

Into a 500-ml, ^" three-necked flask equipped with an addition funnel, thermometer and nitrogen inlet was placed 14.1 g (0.17 mole) of sodium nitrate and 135 ml of concentrated sulfuric acid. The mixture was stirred under nitrogen while cooling to -5°C (calcium chloride/ice) and 19.5 g (0.16 mole) of 1-cyanobenzocyclobutene was added dropwise at such a rate as to keep the reaction temperature below 2°C. The reaction mixture was then stirred under nitrogen at 0°C-5 ^Q C for 0.5 hour, poured onto 1050 g of ice, and extracted with four 300-ml portions of methylene chloride. The methylene chloride solutions were combined, washed with four 150-ml portions of 10 percent

sodium bicarbonate, once with 300 ml of water, and dried over anhydrous magnesium sulfate. The methylene chloride solution was filtered and evap¬ orated on a rotary evaporator to give 26.9.g of residue which was recrystallized from absolute ethanol to give pure 5-nitro-l-cyanobenzocyclobu- ^" tene identified by infrared, Η and 13C nuclear magnetic resonance. The melting point was 110°C-

-112°C and the yield was 64.1 percent.

10 (f) Preparation of 5-Amino-

-1-Cyanobenzocyclobutene

Into a 1-liter, three-necked flask equipped with a gas dispersion tube, reflux con¬ denser, rubber septum and nitrogen inlet was placed

15 _. 7 g (0.04 mole) of 5-nitro-l-cyanobenzocyclobutene and 400 ml of absolute 2B ethanol. The mixture was stirred under nitrogen and heat was applied to dis¬ solve the solid. After adding 2.4 ml of glacial acetic acid and 1.6 g of 5 percent palladium on 0 carbon, hydrogen flow was initiated and the mix¬ ture was hydrogenated at atmospheric pressure and ambient temperature. The hydrogenation was followed by thin-layer chromatography (silica gel; 70 per¬ cent toluene, 25 percent ethyl acetate, 5 percent 5 triethylamine as eluent) and this showed the reac- •tion was essentially complete in 1 hour. After 3 hours, the hydrogen flow was stopped and the system was purged with nitrogen for 15 minutes to remove excess hydrogen gas. The catalyst was removed by 0 filtration using Celite and quickly quenched in water. The filtrate was evaporated to dryness on

a rotary evaporator and the residue was. treated with aqueous 10 percent sodium hydroxide. The aqueous solution was extracted with three 100-ml portions of ethyl ether, and the solutions were 5 combined and washed once with 100 ml of water.

The ethyl ether solution was dried over anhydrous ^" potassium carbonate, filtered and evaporated on a rotary evaporator to give an amber-colored oil that solidified on standing. The product was pumped 10 under vacuum overnight to remove the last traces of ethyl ether and stored under nitrogen. The fra- rreedd,, ΗΗ aanndd 1 133CC nnuucclleeaarr mmaagcnetic resonance were run.

The yield was 86.4 percent.

(g) Preparation of'N-[5-(l-Cyano-- 15 benzocyclobutenyl)]maleamic Acid

Into a 250-ml, three-necked flask equipped with a mechanical stirrer, addition fun¬ nel, reflux condenser, thermometer and nitrogen inlet was placed 4.9 g (0.05 mole) of freshly sub-

2.0 limed maleic anhydride and 50 ml of dry chloroform. The mixture was stirred under nitrogen while cooling to 15°C in an ice bath and a solution of 7 g (0.05 mole) of 5-amino-l-cyanobenzocyclobutene in 50 ml of dry chloroform was added dropwise at such a rate

25 as to keep the reaction mixture below 20 ° . The reaction was maintained below 20°C and stirred under nitrogen for 1 hour after addition was complete. The solid N-[5-(l-cyanobenzocyclobutenyl)]maleamic acid was filtered off, washed with cold chloroform,

30 then with hot ethyl acetate/ethanol (absolute;

1:1 v/v), and dried overnight in a vacuum oven at

60°C. The infrared, 'H and 13C nuclear magnetic resonance, and carbon, hydrogen, nitrogen analyses were run and are given below.

Analysis Calculated Found carbon 64.46. 63.80 hydrogen 4.16 4.44 nitrogen 11.57 11.36

The yield was 11.32 g equal to 94.25 percent and the melting point was 190°C-192°C.

Example 2 - Preparation of N-[5-(l-Cyano- benzocyclobutenyl)jmaleimide

Into a 250-ml, three-necked flask equipped with a mechanical stirrer, reflux con¬ denser, thermometer and nitrogen inlet was placed 11 g (0.045 mole) of N-[5-(l-cyanobenzocyclobuten- yl)]maleamic acid, 2.4 g (0.03 mole) of anhydrous sodium acetate, and 45.94 g (0.765 mole) of fresh glacial acetic acid. The mixture was stirred and slowly heated under nitrogen until a clear yellow solution resulted (117°C-118°C) . After 5 minutes the heat was removed and the reaction mixture was allowed to cool under nitrogen overnight at room temperature. It was then slowly poured into a vig¬ orously stirred slurry of ice and water (120 g total), and the resulting yellow precipitate fil¬ tered, washed with water until neutral to litmus, and transferred to a 500-ml beaker containing 150 ml of aqueous saturated sodium bicarbonate. This mixture was stirred for 10 minutes, then 150 ml of

chloroform was added and stirred for an additional 10 minutes. The organic layer was taken up in three 50-ml portions of chloroform, and the solutions were combined and washed once with 150 ml of water. The chloroform solution was dried over anhydrous magne¬ sium sulfate, filtered and evaporated on a rotary evaporator to give a viscous yellow oil. The prod¬ uct was pumped under vacuum overnight to give a yel¬ low solid that was purified by column chromatography on silica gel using 70 percent toluene/30 percent ethyl acetate as the eluent. The infrared, Η and C nuclear magnetic resonance, and carbon, hydro¬ gen, nitrogen analyses were run, and the results are given below.

Analysis Calculated Found carbon 69.60 69.30 hydrogen 3.60 3.70 nitrogen 12.50 12.34

The yield was 5.7 g equal to 56.5 percent. The melting point was 55°C-60°C.

Example 3 - Polymerization of N-[5-(l-Cyano- benzocyclobutenyl)]maleamic acid

In a 25-ml one-neck flask equipped with a nitrogen purge tube was placed 0.1127 g of N-[5-(l- -cyanobenzocyclobutenyl)]maleamic acid and 10 drops of water. To this was added 4 drops of concentrated (15M) ammonia water. All of the solids dissolve. Nitrogen was bubbled through the solution until all the excess ammonia was gone. The solution was then

coated onto microscope slides, and the water was allowed ^a to evaporate at room temperature. The slides were then heated in air at 175°C for 20 minutes to form a polymer coating. The coating was pale yellow transparent coating which was unaffected by organic solvents and thermally stable to greater than 320°C.