FENG XIANGDONG (CN)
SPINDLER FELIX (CH)
PUGIN BENOIT (CH)
FENG XIANGDONG (CN)
SPINDLER FELIX (CH)
| WO2005108409A2 | 2005-11-17 |
Claims
1. Compounds of the formulae I and Ia in the form of mixtures of diastereomers or pure diastereomers,
Ri is a hydrogen atom or Ci-C 4 -alkyl and R'i is Ci-C 4 -alkyl; Xi and X2 are each, independently of one another, a sec-phosphino group; T is C6-C2o-arylene or C4-Cis-heteroarylene having heteroatoms selected from the group consisting of O, S, -N= and N(Ci-C 4 -alkyl); v is 0 or an integer from 1 to 4;
Xi is bound in the ortho position relative to the T-C * bond; Q is vinyl, methyl, ethyl, -CH 2 -OR, -CH 2 -N(Ci-C 4 -alkyl) 2 or a C- or S-bonded chiral group which directs metals of metallation reagents into the ortho position; R is hydrogen, a silyl radical or an aliphatic, cycloaliphatic, aromatic or aromatic- aliphatic hydrocarbon radical which has from 1 to 18 carbon atoms and is unsubstituted or substituted by Ci-C4-alkyl, Ci-C4-alkoxy, F or CF 3 ; and * denotes a mixture of diastereomers or pure diastereomers.
2. Compounds according to Claim 1 , characterized in that the compounds are compounds of the formula Ib or Ic,
where Q, Ri, R'i, Xi, X2 and v and also * have the meanings given in Claim 1. 3. Compounds according to Claim 1 , characterized in that sec-phosphino radicals Xi and X2 are, independently of one another, acyclic sec-phosphino selected from the group consisting of -P(Ci-C6-alkyl) 2 , -P(C 5 -C8-cycloalkyl) 2 , -P(C 7 -C8-bicycloalkyl) 2 , -P(o-furyl) 2 , -P(C 6 Hs) 2 , -P[2-(Ci-C 6 -alkyl)C 6 H4] 2 , -P[3-(Ci-C 6 -alkyl)C 6 H4] 2 , -P[4-(Ci-C 6 - alkyl)C 6 H 4 ] 2 , -P[2-(Ci-C 6 -alkoxy)C 6 H 4 ] 2 , -P[3-(Ci-C 6 -alkoxy)C 6 H 4 ] 2 , -P[4-(Ci-C 6 - alkoxy)C 6 H 4 ] 2 , -P[2-(trifluoromethyl)C 6 H 4 ] 2 , -P[3-(trifluoromethyl)C 6 H 4 ] 2 , -P[4-(trifluoro- methyl)C 6 H 4 ] 2 , -P[3,5-bis(trifluoromethyl)C 6 H 3 ] 2 , -P[3,5-bis(Ci-C 6 -alkyl) 2 C 6 H 3 ] 2 , -P[3,5-bis(Ci-C 6 -alkoxy) 2 C 6 H 3 ] 2 and -P[3,5-bis(Ci-C 6 -alkyl) 2 -4-(Ci-C 6 -alkoxy)C 6 H 2 ] 2 , or a cyclic phosphino group selected from the group consisting of
which are unsubstituted or substituted by one or more Ci-C 4 -alkyl, Ci-C 4 -alkoxy, Ci-C 4 -alkoxy-Ci-C 2 -alkyl, phenyl, benzyl, benzyloxy or Ci-C 4 -alkylidenedioxyl radicals.
4. Compounds according to Claim 1 , characterized in that the group Q corresponds to the formula -HC * R 5 R6, where R 5 is Ci-C 8 -alkyl, C 5 -C 8 -cycloalkyl, phenyl or benzyl, R 6 is -OR 7 or -NR 8 Rg, R 7 is Ci-C 8 -alkyl, C 5 -C 8 -cycloalkyl, phenyl or benzyl and R 8 and Rg are identical or different and are each Ci-C 8 -alkyl, C 5 -C 8 -cycloalkyl, phenyl or benzyl or R 8 and Rg together with the N atom form a five- to eight-membered N- heterocyclic ring.
5. Compounds according to Claim 4, characterized in that R 5 is Ci-C 4 -alkyl or phenyl, R 7 is Ci-C 4 -alkyl, R 8 and Rg are identical radicals and are each Ci-C 4 -alkyl or together form tetramethylene, pentamethylene or 3-oxa-1 ,5-pentylene.
6. Process for preparing compounds according to the invention of the formulae I and Ia, which comprises the steps: a) reaction of a compound of the formula II, Na or a mixture thereof,
Q and Ri have the meanings given in Claim 1 with the exception of Q = - CH 2 OH and halogen is bromine or iodine, with at least equivalent amounts of an aliphatic Li sec-amide or a halogen-Mg sec-amide to form a compound of the formula III, Ilia or a mixture thereof,
b) reaction of a compound of the formula III or Ilia with a compound of the formula X 2 -HaIo, where Halo is Cl, Br or I, to introduce the group X 2 and form a compound of the formula IV or IVa;
c1 ) an α-sec-phosphinobenzaldehyde of the formula
A
(R\); \
CHO or c2) firstly with a dialkylformamide to form a ferrocenealdehyde of the formula V or Va
then with an organometallic compound of the formula
d) to prepare compounds in which Q is -CH2OH, derivatization of the -CH2OR group.
7. Compounds of the formulae V and Va
8. Complexes of metals selected from the group of transition metals Fe, Co, Ni, Cu, Ag, Au, Ru, Rh, Pd, Os and Ir, with one of the compounds of the formula I and/or Ia as a ligand.
9. Process for preparing chiral organic compounds by asymmetric addition of hydrogen onto a carbon-carbon or carbon-heteroatom double bond in prochiral organic compounds in the presence of a catalyst, which is characterized in that the addition reaction is carried out in the presence of catalytic amounts of at least one metal complex according to Claim 8.
10. Use of the metal complexes according to Claim 8 as homogeneous catalysts for the preparation of chiral organic compounds, preferably for the asymmetric addition of hydrogen onto a carbon-carbon or carbon-heteroatom double bond in prochiral organic compounds. |
Diphosphine ligands
The present invention relates to 1-sec-phosphino-2-[(2'-sec-phosphino)hydroxy- benzyl]ferrocenes having a further substituent in the 3 position of the cyclo- pentadienyl ring and also derivatives of these compounds, their preparation, complexes of transition metals with these ligands and the use of the metal complexes in the homogeneous, stereoselective synthesis of organic compounds.
Chiral ligands have proven to be extraordinarily important auxiliaries for catalysts in homogeneous stereoselective catalysis. The effectiveness of such catalysts frequently proves to be specific for particular substrates. To be able to achieve optimization for particular substrates, it is therefore necessary to have a sufficiently large number of chiral ligands available. There is thus a continual need for further efficient chiral ligands which are simple to prepare and give good results in stereoselective catalytic reactions. Ligands whose properties can be adapted and optimized for particular catalytic objectives are of particular interest. Ligands which can be built up in a modular fashion are particularly suitable for this purpose.
Ferrocene is a very useful skeleton for the preparation of ligands which has been used successfully for providing different substitutions with secondary phosphino radicals. WO 00/037478 describes ligands of the formula
WO 2005/068477 describes the preparation of ferrocenediphosphines having a chiral P atom. For the preparation of ligands of the Taniaphos type, this document proposes
firstly introducing an R'R"P- radical into a ferrocene having an ortho-directing auxiliary group in the metallation, then hydrolyzing the auxiliary group to an aldehyde group and then reacting the aldehyde group with an orthometallated sec-phosphinobenzene. The use of a hydrolyzable chiral auxiliary group makes the process expensive and uneconomical. According to WO 2005/108409, a P(III) group is used as ortho-directing chiral auxiliary group, with the product of the metallation being reacted with an o-sec- phosphinobenzaldehyde and the P(III) auxiliary group then being converted into a sec- phosphino group. This synthesis is considered to be complicated. The compounds of the formula
There is a great need for ligands of the Taniaphos-OH type which can be prepared in a simple, modular and economical way and are suitable as ligands for metal complexes in asymmetric catalysts.
It has now surprisingly been found that the preparation of optically pure isomers of the Taniaphos-OH type can be achieved particularly simply when a ferrocene in which an optionally modifiable ortho-directing chiral group is bound to one Cp ring is used as starting material. The presence of a further optical centre leads to excellent diastereoselectivities in the synthesis of bidentate ligands and additionally allows simple purification or separation of the stereoisomers by crystallization or by preparative chromatography, even on achiral columns.
Furthermore, it has surprisingly been found that these ligands, which contain a further substituent in the cyclopentadienyl ring (Cp) in the ortho position relative to the Cp-CHOH bond, have an at least about equally good effect in metal complexes for enantioselective and homogeneous catalysts as Taniaphos-OH and enable,
depending on the prochiral substrate, very good to very high stereoselectivities to be achieved. The choice of this substituent makes it possible to influence the catalytic properties and to optimize them for particular substrates.
The invention firstly provides compounds of the formulae I and Ia in the form of mixtures of diastereomers or pure diastereomers,
where
Ri is a hydrogen atom or Ci-C 4 -alkyl and R'i is Ci-C 4 -alkyl; Xi and X2 are each, independently of one another, a sec-phosphino group; T is C6-C 2 o-arylene or C4-Cis-heteroarylene having heteroatoms selected from the group consisting of O, S, -N= and N(Ci-C 4 -alkyl); v is 0 or an integer from 1 to 4;
Xi is bound in the ortho position relative to the T-C * bond;
Q is vinyl, methyl, ethyl, -CH 2 -OR, -CH 2 -N(Ci-Ci 2 -alkyl) 2 or a C- or S-bonded chiral group which directs metals of metallation reagents into the ortho position; R is hydrogen, a silyl radical or an aliphatic, cycloaliphatic, aromatic or aromatic- aliphatic hydrocarbon radical which has from 1 to 18 carbon atoms and is unsubstituted or substituted by Ci-C4-alkyl, Ci-C4-alkoxy, F or CF3; and * denotes a mixture of diastereomers or pure diastereomers.
Preferred compounds according to the invention are compounds of the formula Ib or Ic,
- A -
where Q, Ri, R'i, Xi, X2 and v and also * have the above meanings.
Ri can be present once or twice or from one to five times in the cyclopentadienyl rings. An alkyl radical Ri can be, for example, methyl, ethyl, n- or i-propyl, n-, i- or t-butyl, with preference being given to methyl. Ri is preferably a hydrogen atom. R'i can be present from one to four times in the aromatic or heteroaromatic radical T. Preference is given to v being 0 and R'i thus being hydrogen.
An alkyl radical R'i can be, for example, methyl, ethyl, n- or i-propyl, n-, i- or t-butyl, with preference being given to methyl.
An arylene radical T preferably has from 6 to 14 carbon atoms. Examples of arylene are phenylene, naphthylene, anthracylene and phenanthrylene. Preference is given to 1 ,2-phenylene and 1 ,2-naphthylene.
A heteroarylene radical T preferably has from 4 to 14 carbon atoms and particularly preferably from 4 to 5 carbon atoms and preferably one heteroatom. Examples of heteroarylene are 1 ,2- or 2,3-thiophenylene, 1 ,2- or 2,3-furanylene and N-methyl-1 ,2- or -2,3-pyrrolylene and also 2,3- or 3,4-pyridinylene.
Xi and X2 can be secondary phosphino groups which contain identical or different hydrocarbon radicals and/or heterohydrocarbon radicals. Furthermore, Xi and X2 can be identical or different.
The hydrocarbon radicals can be unsubstituted or substituted and/or contain hetero- atoms selected from the group consisting of O, S, -N= and N(Ci-C 4 -alkyl). They can contain from 1 to 22, preferably from 1 to 12 and particularly preferably from 1 to 8, carbon atoms. A preferred sec-phosphino group is one in which the phosphino group contains two identical or different radicals selected from the group consisting of linear or branched Ci-Ci2-alkyl; unsubstituted or Ci-C6-alkyl- or Ci-Cβ-alkoxy-substituted C 5 -Ci2-cycloalkyl or C 5 -Ci2-cycloalkyl-CH 2 -; phenyl, naphthyl, furyl and benzyl; and
halogen-, Ci-C 6 -alkyl-, trifluoromethyl-, Ci-C 6 -alkoxy-, trifluoromethoxy-, (C 6 H 5 )3Si-, (Ci-Ci2-alkyl) 3 Si- or sec-amino-substituted phenyl or benzyl.
Examples of alkyl substituents on P, which preferably contain from 1 to 6 carbon atoms, are methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl and the isomers of pentyl and hexyl. Examples of unsubstituted or alkyl-substituted cycloalkyl substituents on P are cyclopentyl, cyclohexyl, methylcyclohexyl and ethylcyclohexyl and dimethylcyclohexyl. Examples of alkyl- and alkoxy-substituted phenyl and benzyl substituents on P are methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl, methylbenzyl, methoxyphenyl, dimethoxyphenyl, trimethoxyphenyl, trifluoromethyl- phenyl, bistrifluoromethylphenyl, tristrifluoromethylphenyl, trifluoromethoxyphenyl, bistrifluoromethoxyphenyl, fluorophenyl and chlorophenyl and 3,5-dimethyl- 4-methoxyphenyl.
Preferred secondary phosphino groups are ones which have identical or different radicals selected from the group consisting of Ci-Cε-alkyl, unsubstituted cyclopentyl or cyclohexyl and cyclopentyl or cyclohexyl bearing from 1 to 3 Ci-C 4 -alkyl or C 1 -C 4 - alkoxy groups as substituents, benzyl and in particular phenyl which are unsubstituted or substituted by from 1 to 3 Ci-C4-alkyl, Ci-C4-alkoxy, Ci-C4-fluoroalkyl or Ci-C4-fluoroalkoxy, F and Cl radicals.
The sec-phosphino group preferably corresponds to the formula -PR2R3, where R2 and R 3 are each, independently of one another, a hydrocarbon radical which has from 1 to 18 carbon atoms and is unsubstituted or substituted by Ci-Cε-alkyl, trifluoromethyl, Ci-C6-alkoxy, trifluoromethoxy, (Ci-C4-alkyl) 2 amino, (CeHs) 3 Si, (Ci-Ci2-alkyl) 3 Si or halogen and/or contains heteroatoms O.
R 2 and R 3 are preferably radicals selected from the group consisting of linear or branched Ci-Cε-alkyl, unsubstituted cyclopentyl or cyclohexyl and cyclopentyl or cyclohexyl bearing from one to three Ci-C4-alkyl or Ci-C4-alkoxy groups as substituents, furyl, unsubstituted benzyl and benzyl bearing from one to three Ci-C4-alkyl or Ci-C4-alkoxy groups as substituents and in particular unsubstituted phenyl and
phenyl bearing from one to three F, Cl, Ci-C 4 -alkyl, Ci-C 4 -alkoxy, Ci-C 4 -fluoroalkyl or Ci-C4-fluoroalkoxy radicals as substituents.
R 2 and R3 are particularly preferably radicals selected from the group consisting of Ci-Cβ-alkyl, cyclopentyl, cyclohexyl, furyl and unsubstituted phenyl and phenyl substituted by from one to three F, Cl, Ci-C4-alkyl, Ci-C4-alkoxy and/or Ci-C4-fluoroalkyl radicals.
When R 2 and R3 in the -PR2R3 group are different, the ligands are additionally P-chiral.
The secondary phosphino group can be cyclic sec-phosphino, for example a group having one of the formulae
which are unsubstituted or substituted one or more times by Ci-Cs-alkyl, C4-C8- cycloalkyl, Ci-Cε-alkoxy, Ci-C 4 -alkoxy-Ci-C 4 -alkyl, phenyl, Ci-C 4 -alkylphenyl or Ci-C 4 -alkoxyphenyl, benzyl, Ci-C 4 -alkylbenzyl or Ci-C 4 -alkoxybenzyl, benzyloxy, Ci-C4-alkylbenzyloxy or Ci-C4-alkoxybenzyloxy or Ci-C4-alkylidenedioxyl.
The substituents can be bound in one or both α positions relative to the P atom in order to introduce chiral carbon atoms. The substituents in one or both α positions are preferably Ci-C 4 -alkyl or benzyl, for example methyl, ethyl, n- or i-propyl, benzyl or -CH 2 -O-Ci-C 4 -alkyl or -CH 2 -O-C 6 -Ci 0 -aryl.
Substituents in the β,γ positions can be, for example, Ci-C4-alkyl, Ci-C4-alkoxy, benzyloxy or -0-CH 2 -O-, -O-CH(Ci-C 4 -alkyl)-O- and -O-C(Ci-C 4 -alkyl) 2 -O-. Some examples are methyl, ethyl, methoxy, ethoxy, -O-CH(methyl)-O- and -O-C(methyl) 2 -O-
Depending on the type of substitution and number of substituents, the cyclic phosphino radicals can be C-chiral, P-chiral or C- and P-chiral.
In the radicals of the above formulae, an aliphatic 5- or 6-membered ring or benzene can be fused onto two adjacent carbon atoms.
The cyclic sec-phosphino group can, for example, correspond to the formulae (only one of the possible diastereomers is shown)
where the radicals R' and R" are each Ci-C4-alkyl, for example methyl, ethyl, n- or i-propyl, benzyl or -CH 2 -O-Ci-C 4 -alkyl or -CH 2 -0-C 6 -Cio-aryl and R' and R" are identical or different.
In the compounds of the formulae I, sec-phosphino radicals Xi and X 2 are, independently of one another, preferably acyclic sec-phosphino selected from the group consisting of -P(Ci-C 6 -alkyl) 2 , -P(C 5 -C 8 -cycloalkyl) 2 , -P(C 7 -C 8 -bicycloalkyl) 2 , -P(o-furyl) 2 , -P(C 6 Hs) 2 , -P[2-(Ci-C6-alkyl)C 6 H 4 ] 2 , -P[3-(Ci-C6-alkyl)C 6 H 4 ] 2 , -P[4-(Ci-C6-alkyl)C 6 H 4 ] 2 , -P[2-(Ci-C 6 -alkoxy)C 6 H 4 ] 2 , -P[3-(Ci-C 6 -alkoxy)C 6 H 4 ] 2 , -P[4-(Ci-C 6 -alkoxy)C 6 H 4 ] 2 , -P[2-(trifluoromethyl)C 6 H 4 ] 2 , -P[3-(trifluoromethyl)C 6 H 4 ] 2 , -P[4-(trifluoromethyl)C 6 H 4 ] 2 , -P[3,5-bis(trifluoromethyl)C 6 H 3 ] 2 , -P[3,5-bis(Ci-C 6 -alkyl) 2 C 6 H 3 ] 2 , -P[3,5-bis(Ci-C 6 -
alkoxy) 2 C 6 H 3 ]2 and -P[3,5-bis(Ci-C 6 -alkyl)2-4-(Ci-C6-alkoxy)C 6 H2]2, or a cyclic phosphino group selected from the group consisting of
which are unsubstituted or substituted by one or more Ci-C4-alkyl, Ci-C4-alkoxy, Ci-C 4 -alkoxy-Ci-C 2 -alkyl, phenyl, benzyl, benzyloxy or Ci-C 4 -alkylidenedioxyl radicals.
Some specific examples are -P(CH 3 ) 2 , -P(i-C 3 H 7 )2, -P(n-C 4 H 9 ) 2 , -P(i-C 4 H 9 ) 2 , -P(t-C 4 H 9 ) 2 , -P(C 5 H 9 ), -P(C 6 Hn) 2 , -P(norbornyl) 2 , -P(o-furyl) 2 , -P(C 6 Hs) 2 , P[2-(methyl)C 6 H 4 ] 2 , P[3-(methyl)C 6 H 4 ] 2 , -P[4-(methyl)C 6 H 4 ] 2 , -P[2-(methoxy)C 6 H 4 ] 2 , -P[3-(methoxy)C 6 H 4 ] 2 , -P[4-(methoxy)C 6 H 4 ] 2 , -P[3-(trifluoromethyl)C 6 H 4 ] 2 , -P[4-(trifluoromethyl)C 6 H 4 ] 2 , -P[3,5-bis(trifluoromethyl)C 6 H 3 ] 2 , -P[3,5- bis(methyl) 2 C 6 H 3 ] 2 , -P[3,5-bis(methoxy) 2 C 6 H 3 ] 2 and -P[3,5-bis(methyl) 2 -4- (methoxy)C 6 H 2 ] 2 and groups of the formulae
where
R' is methyl, ethyl, methoxy, ethoxy, phenoxy, benzyloxy, methoxymethyl, ethoxy- methyl or benzyloxymethyl and R" independently has the same meanings as R' and is different from R'.
In the ortho-directing, chiral group Q, the chiral atom is preferably bound in the 1 , 2 or 3 position relative to the cyclopentadienyl-Q bond. The group Q can be a substituted or unsubstituted open-chain radical having from 1 to 20 and preferably from 1 to 12 atoms or a cyclic radical having 4 or 8 ring atoms and a total of from 4 to 20 and preferably from 4 to 16 atoms, with the atoms being selected from the group consisting of C, O, S, N and P. The hydrogen atoms on C, O, S, N and P atoms are not counted.
The group Q can be, for example, a sulphoxyl radical of the formula -S * (=O)-R4, where R 4 is Ci-Cs-alkyl and preferably C 2 -C 6 -alkyl or C 5 -Cs-cycloalkyl or C 6 -Cio-aryl. Some examples are methylsulphoxyl, ethylsulphoxyl, n- or i-propylsulphoxyl and n-, i- or t-butylsulphoxyl and phenylsulphoxyl.
The group Q can, for example, correspond to the formula -HC * RsR6 (the chiral atom is denoted by *) where R 5 is Ci-Cs-alkyl, Cs-Cs-cycloalkyl, phenyl or benzyl, R 6 is -OR 7 or -NR 8 Rg, R 7 is Ci-Cs-alkyl, Cs-Cs-cycloalkyl, phenyl or benzyl and Rs and Rg are identical or different and are each Ci-Cs-alkyl, Cs-Cs-cycloalkyl, phenyl or benzyl or R 8 and Rg together with the N atom form a five- to eight-membered ring. R 5 is preferably Ci-C 4 -alkyl such as methyl, ethyl, n-propyl or phenyl. R 7 is preferably Ci-C 4 -alkyl such as methyl, ethyl, n-propyl or n- or i-butyl. Rs and Rg are preferably identical radicals and are each preferably Ci-C 4 -alkyl such as methyl, ethyl, n-propyl or n- or i-butyl or together form tetramethylene, pentamethylene or 3-oxa-1 ,5-pentylene. Particularly preferred groups of the formula -HCRsRε are 1-methoxyeth-1-yl, 1-dimethylaminoeth- 1-yl and 1-(dimethylamino)1-phenylmethyl.
When Q is an achiral, ortho-directing group -CH 2 -N(Ci-Ci2-alkyl) 2 , the alkyl group is preferably linear alkyl and very particularly preferably methyl or ethyl.
When Q is an achiral, ortho-di recti ng group -CH2-OR, R as hydrocarbon radical is, for example, alkyl, cycloalkyl, heterocycloalkyl, cycloalkylalkyl, heterocycloalkylalkyl, aryl, aralkyl, heteroaryl, heteroaralkyl containing heteroatoms selected from the group consisting of O, S, -N= or -N(Ci-C4-alkyl), where cyclic radicals preferably have from
5 to 7 ring members, alkyl preferably has from 1 to 6 carbon atoms and "alkyl" in cyclic radicals preferably has 1 or 2 carbon atoms. In a preferred embodiment, R as hydrocarbon radical is Ci-C 4 -alkyl, C 5 -C 6 -cycloalkyl, Cε-Cio-aryl, C 7 -Ci 2 -aralkyl or C 7- Ci 2 -alkaralkyl. Some examples of R are methyl, ethyl, n-propyl, n-butyl, cyclo- hexyl, cyclohexylmethyl, tetrahydrofuryl, phenyl, benzyl, furanyl and furanylmethyl.
A silyl radical R in the group -CH 2 -OR can be tri(Ci-C4-alkyl)Si or triphenylsilyl. Examples of trialkylsilyl are trimethylsilyl, triethylsilyl, tri-n-propylsilyl, tri-n-butylsilyl and dimethyl-t-butylsilyl.
When Q is an achiral, ortho-di recti ng group -CH2-OR, R is particularly preferably an alkyl group, preferably linear alkyl and very particularly preferably methyl or ethyl.
When Q is a radical without a chiral α carbon atom, it is bound via a carbon atom to the cyclopentadienyl ring either directly or via a bridging group. The bridging group can be, for example, methylene, ethylene or an imine group. Cyclic radicals bound to the bridging group are preferably saturated and are particularly preferably N-, O- or N,O-heterocycloalkyl substituted by Ci-C 4 -alkyl, (Ci-C 4 -alkyl) 2 NCH 2 -, (Ci-C 4 - alkyl) 2 NCH 2 CH 2 -, Ci-C 4 -alkoxymethyl or Ci-C 4 -alkoxyethyl and having a total of 5 or
6 ring atoms. Open-chain radicals are preferably bound via a CH 2 group to the cyclopentadienyl ring and the radicals are preferably derived from amino acids or ephedrine. Some preferred examples are:
where R 10 is Ci-C 4 -alkyl, phenyl, (Ci-C 4 -alkyl) 2 NCH 2 -, (Ci-C 4 -alkyl) 2 NCH 2 CH 2 -, Ci-C 4 -alkoxymethyl or Ci-C 4 -alkoxyethyl. Rio is particularly preferably methoxymethyl or dimethylaminomethyl.
The compounds of the invention can be obtained via a novel process starting out from ferrocenes which are halogenated in the α position relative to a substituent Q and can be metallated regioselectively and chemoselectively in the ortho position relative to the halogen atom by metal amides. The metal atom can then be replaced in a known manner by the group X 2 . The α-bromine atom can then be metallated in order to introduce the -C H(OH)-T-Xi group, with precisely these last stages involving formation of the asymmetric C - atom leading to astonishingly high diastereoselectivities.
The invention further provides a process for preparing compounds according to the invention of the formulae I and Ia, which comprises the steps: a) reaction of a compound of the formula II, Na or a mixture thereof,
Q and Ri have the above meanings with the exception of Q = -CH 2 OH and halogen is bromine or iodine, with at least equivalent amounts of an aliphatic Li sec-amide or a halogen-Mg sec-amide to form a compound of the formula III, Ilia or a mixture thereof,
b) reaction of a compound of the formula III or Ilia with a compound of the formula X2-Halo, where Halo is Cl, Br or I, to introduce the group X2 and form a compound of the formula IV or IVa,
c) introduction of the group -(CH(OH)-T(R'i) v -Xi by reaction of a compound of the formula IV or IVa with at least equivalent amounts of alkyllithium or a magnesium Grignard compound and then with at least equivalent amounts of c1 ) an α-sec-phosphinobenzaldehyde of the formula
or c2) firstly with a dialkylformamide to form a ferrocenealdehyde of the formula V or Va
where R'i, Xi, T, M and v have the above meanings and M is bound in the ortho position relative to Xi to give a compound of the formula I or Ia; and d) to prepare compounds in which Q is -CH 2 OH, derivatization of the -CH 2 OR group.
Compounds of the formulae Il and Na in which Q is methyl, for example 1-methyl-2- bromoferrocene, are described by T. Arantani et al. in Tetrahedron 26 (1970), pages 5453-5464, and by T. E. Picket et al. in J. Org. Chem. 68 (2003), pages 2592-2599.
Compounds of the formulae Il and Na in which Q is vinyl or ethyl can, for example, be prepared by elimination of amines in 1-[(dialkylamino)eth-1-yl]-2-haloferrocenes, for example 1-[(dimethylamino)eth-1-yl]-2-bromoferrocene of the formula
Compounds of the formulae Il and Na in which Q is a -CH 2 -N(Ci-Ci 2 -alkyl) 2 group can be obtained, for example, by substitution of a quaternized CH 2 -bonded chiral sec- amino radical by HN(Ci-C4-alkyl) 2 . Examples of such CH 2 -bonded sec-amino radicals are those of the formulae
where
Rio is Ci-C 4 -alkyl, phenyl, (Ci-C 4 -alkyl) 2 NCH 2 -, (Ci-C 4 -alkyl) 2 NCH 2 CH 2 -, d-C 4 - alkoxymethyl or Ci-C 4 -alkoxyethyl. R 10 is particularly preferably methoxymethyl or dimethylaminomethyl. Quaternization is advantageously carried out by means of alkyl halides (alkyl iodides), for example methyl iodide.
Compounds of the formulae Il and Na in which Q is -CH 2 -OR can be obtained by firstly acyloxylating (for example to 1-acetyloxy-CH 2 -) 1-(Ci-C 4 -alkyl) 2 NCH 2 -2- haloferrocene by means of carboxylic anhydrides, for example acetic anhydride, to form 1-acyloxy-CH 2 -2-haloferrocene and then reacting these intermediates with alcohols in the presence of bases or with alkali metal alkoxides to give 1-RO-CH 2 -2- haloferrocene. Compounds of the formula Il in which Q is -HCR5-OR7 can be obtained in an analogous way by modification of the group Q = -HCRs-N(Ci-C 4 - alkyl) 2 with alcohols HOR 7 .
Surprisingly, the regioselectivity in the metallation in the ortho position relative to the bromine atom for subsequent introduction of electrophiles is essentially maintained even in the presence of the groups vinyl, methyl, ethyl, -CH 2 -OR and (CrC 4 - alkyl) 2 NCH 2 -.
Metallations of ferrocenes using alkyllithium or magnesium Grignard compounds are known reactions which are described, for example, by T. Hayashi et al., Bull. Chem. Soc. Jpn. 53 (1980), pages 1138 to 1151 , or in Jonathan Clayden Organolithiums: Selectivity for Synthesis (Tetrahedron Organic Chemistry Series), Pergamon Press (2002). The alkyl in the alkyllithium can contain, for example, from 1 to 4 carbon atoms. Use is frequently made of methyllithium and butyllithium. Magnesium
Grignard compounds are preferably compounds of the formula (Ci-C4-alkyl)MgXo, where Xo is Cl, Br or I.
The reaction is advantageously carried out at low temperatures, for example from 20 to -100 0 C, preferably from 0 to -80 0 C. The reaction time is from about 1 to 20 hours. The reaction is advantageously carried out under inert protective gases, for example nitrogen or noble gases such as helium or argon.
The reaction is advantageously carried out in the presence of inert solvents. Such solvents can be used either alone or as a combination of at least two solvents. Examples of solvents are aliphatic, cycloaliphatic and aromatic hydrocarbons and also open-chain or cyclic ethers. Specific examples are petroleum ether, pentane, hexane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, diethyl ether, dibutyl ether, tert-butyl methyl ether, ethylene glycol dimethyl or diethyl ether, tetrahydrofuran and dioxane.
The halogenation is generally carried out immediately after the metallation in the same reaction mixture, with similar reaction conditions as in the metallation being maintained. For the purposes of the invention, "an at least equivalent amount" means the use of preferably from 1 to 1.4 equivalents of a halogenating reagent. Halogena- ting reagents are, for example, halogens (Br 2 , I 2 ), interhalogens (Cl-Br, Cl-I) and aliphatic, perhalogenated hydrocarbons [HCI3 (iodo form), BrF 2 C-CF 2 Br or 1 ,1 ,2,2- tetrabromoethane] for the introduction of Br or I.
The metallation and the halogenation proceed regioselectively and the compounds of the formulae Il are obtained in high yields. The reaction is also stereoselective due to the presence of the chiral group Q. Furthermore, if necessary, optical isomers can also be separated off at this stage, for example chromatographically by means of chiral columns.
In process step a), the ferrocene skeleton is once again regioselectively metallated in the same cyclopentadienyl ring in the ortho position relative to the halogen atom in
formula Il or Na. Here, metal amides are sufficient to replace the acidic H atom in the ortho position relative to the halogen atom. For the purposes of the invention, "at least equivalent amounts" means the use of from 1 to 10 equivalents of an aliphatic Li sec-amide or an X 0 Mg-sec-amide per CH group in the cyclopentadienyl ring of the ferrocene. Xo is Cl, Br or iodine.
Aliphatic Li sec-amide or XoMg-sec-amide can be derived from secondary amines containing from 2 to 18, preferably from 2 to 12 and particularly preferably from 2 to 8 carbon atoms. The aliphatic radicals bound to the N atom can be alkyl, cycloalkyl or cycloalkylalkyl, or the radicals together with the N atom can form N-heterocyclic rings having from 4 to 12 and preferably from 5 to 7 carbon atoms. Examples of radicals bound to the N atom are methyl, ethyl, n- and i-propyl, n-butyl, pentyl, hexyl, cyclo- pentyl, cyclohexyl and cyclohexylmethyl. Examples of N-heterocyclic rings are pyrrolidine, piperidine, morpholine, N-methylpiperazine, 2,2,6,6-tetramethylpiperidine and azanorbornane. As an alternative, it is also possible to use Li sec-amides or XoMg-sec-amides to whose amide nitrogen two trialkylsilyl radicals are bound. In a preferred embodiment the amides correspond to the formula Li-N(C3-C4-alkyl)2 or XoMg-N(C3-C4-alkyl)2, where alkyl is in particular i-propyl. In another preferred embodiment, the amides are Li(2,2,6,6-tetramethylpiperidine).
The reaction of process step a) can be carried out in the above-described solvents and under the reaction conditions for the preparation of the compounds of the formulae Il and Na. The reaction temperature here should be no higher than -10 0 C, preferably -30 0 C or below. The compounds of the formulae III and Ilia are generally not isolated but instead the reaction mixture obtained is preferably used in the subsequent step b).
The reaction of process step b) is carried out using at least equivalent amounts or an excess of up to 1.5 equivalents of a compound of the formula X 2 -HaIo.
In process step b), radicals X 2 are introduced by reaction with compounds of the formula X 2 -HaIo with replacement of M. For the purposes of the invention, "at least
equivalent amounts" means the use of from 1 to 1.2 equivalents of reactive compound per =CM group which reacts in the cyclopentadienyl ring. However, it is also possible to use a distinct excess of up to 5 equivalents.
The reaction is advantageously carried out at low temperatures, for example from 20 to -100 0 C, preferably from 0 to -80 0 C. The reaction is advantageously carried out under an inert protective gas, for example noble gases such as argon or else nitrogen. After addition of the reactive electrophilic compound, the mixture is advantageously allowed to warm to room temperature or is heated to elevated temperatures, for example up to 100 0 C and preferably up to 50 0 C, and stirred for some time under these conditions to complete the reaction.
The reaction is advantageously carried out in the presence of inert solvents. Such solvents can be used either alone or as a combination of at least two solvents. Examples of solvents are aliphatic, cycloaliphatic and aromatic hydrocarbons and also open-chain or cyclic ethers. Specific examples are petroleum ether, pentane, hexane, heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, diethyl ether, dibutyl ether, tert-butyl methyl ether, ethylene glycol dimethyl or diethyl ether, tetrahydrofuran and dioxane.
The compounds of the formula IV can be isolated by known methods (extraction, distillation, crystallization, chromatographic methods) and, if desired, purified in a manner known per se.
The metallation of process step c) is carried out in a manner analogous to the above- described lithiation (using alkyllithium) and substitution reactions. It is possible to use equivalent amounts of lithiating reagent or an excess of up to 1.2 equivalents. The metallation is preferably carried out at a temperature of from -80 to about 30°C. The replacement of the metal is advantageously carried out firstly at temperatures of from +20 to -100°C and then in an after-reaction with heating to up to 80°C. The above- mentioned solvents can be used.
The reaction with α-sec-phosphinobenzaldehyde in process step c1 ) is advantageously carried out in a solvent and at temperatures of from -80 to 80 0 C and preferably from -40 to 40 0 C. After addition of water, the reaction mixture is extracted with an organic solvent and the compound of the invention is isolated in a known manner. Suitable solvents have been mentioned above. α-sec-Phosphinobenzaldehydes are known or can be obtained by analogous methods. The compound obtained can, for example, be purified chromatographically on silica gel columns or be used directly in the next step.
The reaction with a dialkylformamide in process step c2) is advantageously carried out at temperatures of from -30 to 50°C and preferably from -20 to 30 0 C and in a solvent. The reaction mixture is worked up by addition of water and extraction with an organic solvent. Suitable solvents have been mentioned above. Compounds of the formula
used in the next step can be obtained in a simple manner by metallation of 1-bromo- 2-iodoaromatics, subsequent reaction with HaIoXi (Halo is Cl, Br or I) to form 1-bromo-2-Xi-aromatics and subsequent metallation of these by means of alkyl- lithium or alkyl Mg halides. Further details may be found in the examples. The addition of compounds of the formula V or Va and the subsequent reaction are advantageously carried out in a solvent and at temperatures of from -20 to -80°C. Before the work-up, the reaction mixture can be warmed to room temperature and stirred for some time to complete the reaction. The reaction mixture is admixed with water and then extracted with organic solvents. The compounds of the invention are then isolated by removal of the solvent. The crude product can be purified chromatographically over, for example, silica gel columns. Further details are described in the examples.
The compounds of the formulae I and Ia are obtained in good yields and high purities by means of the processes of the invention. The high flexibility in respect of the introduction of the groups Xi and X2 represents a particular advantage of the process
since many different groups Xi can be attached after introduction of the groups X2 in the same intermediate.
Compounds of the formulae I and Ia can be modified (introduction of acyloxy and -OR or -OR 7 or secondary amino groups) in the group Q, for example as described by T. Hayashi et al., Bull. Chem. Soc. Jpn. 53 (1980), pages 1138 to 1151. For the modification, the benzylic OH group is advantageously provided with protective groups known per se in order to avoid secondary reactions. The same modifications which have been described above for the preparation of compounds of the formulae Il and Na are possible. In compounds of the formulae I and Ia in which Ri is hydrogen and Q is -CH 2 -OR, -CH 2 -N(Ci-C4-alkyl) 2 or a C-bonded chiral group which directs metals of metallation reagents into the ortho position Xi, it is possible to introduce a radical Ri which is not hydrogen. Of course, it is also possible for an OH group, for example the benzylic CHOH group or Q as CH 2 OH group, to be derivatized in a manner known per se, for example conversion into an ether, ester, carbonate or urethane. The invention also provides the intermediates of the formulae V and Va
The novel compounds of the formula I and Ia are ligands for complexes of transition metals, preferably selected from the group of Fe, Co, Ni, Cu, Ag, Au, Ru, Rh, Pd, Os and Ir, in particular from the group consisting of Ru, Rh and Ir, which are excellent catalysts or catalyst precursors for asymmetric syntheses, for example the asymmetric
hydrogenation of prochiral, unsaturated, organic compounds. If prochiral unsaturated organic compounds are used, a very high excess of optical isomers can be induced in the synthesis of organic compounds and a high chemical conversion can be achieved in short reaction times. The enantioselectivities and catalyst activities which can be achieved are excellent and in the case of an asymmetric hydrogenation are considerably higher compared to the known catalysts. Furthermore, such ligands can also be used in other asymmetric addition or cyclization reactions.
The invention further provides complexes of metals selected from the group of transition metals of the Periodic Table with one of the compounds of the formula I and/or Ia as ligand.
Possible metals are, for example, Cu, Ag, Au, Ni, Co, Rh, Pd, Ir, Ru and Pt. Preferred metals are rhodium and iridium and also ruthenium, platinum and palladium.
Particularly preferred metals are ruthenium, rhodium and iridium. The metal complexes can, depending on the oxidation number and coordination number of the metal atom, contain further ligands and/or anions. They can also be cationic metal complexes. Such analogous metal complexes and their preparation have been widely described in the literature.
The metal complexes can, for example, correspond to the general formulae Vl and VII, AiMeU (Vl), (AiMeU) (z+) (E-) z (VII), where Ai is one of the compounds of the formula I and/or Ia, the ligands L are identical or different monodentate, anionic or nonionic ligands or identical or different bidentate, anionic or nonionic ligands; r is 2, 3 or 4 when L is a monodentate ligand or r is 1 or 2 when L is a bidentate ligand; z is 1 , 2 or 3;
Me is a metal selected from the group consisting of Rh, Ir and Ru, with the metal having the oxidation state 0, 1 , 2, 3 or 4;
E " is the anion of an oxo acid or complex acid; and the anionic ligands balance the charge of the oxidation state 1 , 2, 3 or 4 of the metal.
The above-described preferences and embodiments apply to the compounds of the formulae I and Ia.
Monodentate nonionic ligands can, for example, be selected from the group consisting of olefins (for example ethylene, propylene), solvating solvents (nitriles, linear or cyclic ethers, unalkylated or N-alkylated amides and lactams, amines, phosphines, alcohols, carboxylic esters, sulphonic esters), nitrogen monoxide and carbon monoxide.
Suitable polydentate anionic ligands are, for example, allyls (allyl, 2-methallyl) or deprotonated 1 ,3-diketo compounds such as acetylacetonate.
Monodentate anionic ligands can, for example, be selected from the group consisting of halide (F, Cl, Br, I), pseudohalide (cyanide, cyanate, isocyanate) and anions of carboxylic acids, sulphonic acids and phosphonic acids (carbonate, formate, acetate, propionate, methylsulphonate, thfluoromethylsulphonate, phenylsulphonate, tosylate).
Bidentate nonionic ligands can, for example, be selected from the group consisting of linear or cyclic diolefins (for example hexadiene, cyclooctadiene, norbornadiene), dinitriles (malononitrile), unalkylated or N-alkylated diamides of carboxylic acids, diamines, diphosphines, diols, dicarboxylic diesters and disulphonic diesters.
Bidentate anionic ligands can, for example, be selected from the group consisting of the anions of dicarboxylic acids, disulphonic acids and diphosphonic acids (for example oxalic acid, malonic acid, succinic acid, maleic acid, methylenedisulphonic acid and methylenediphosphonic acid).
Preferred metal complexes also include those in which E is -Cl " , -Br " , -I " , CIO 4 " , CF 3 SO 3 " , CH 3 SO 3 " , HSO 4 " , (CF 3 SO 2 ^N " , (CF 3 SO 2 ) 3 C " , tetraarylborates such as B(phenyl) 4 " , B[bis(3,5-thfluoromethyl)phenyl] 4 " , B[bis(3,5-dimethyl)phenyl] 4 " , B(C 6 F 5 ) 4 " and B(4-methylphenyl) 4 " , BF 4 " , PF 6 " , SbCI 6 " , AsF 6 " or SbF 6 " .
Very particularly preferred metal complexes which are particularly suitable for hydrogenations correspond to the formulae VIII and IX,
[A 1 Me 2 YiZ] (VIII), [A 1 Me 2 Yi] + Er (IX), where
Ai is one of the compounds of the formulae I and/or Ia;
Me 2 is rhodium or iridium;
Yi is two olefins or a diene;
Z is Cl, Br or I; and
Er is the anion of an oxo acid or complex acid.
The above-described embodiments and preferences apply to the compounds of the formulae I and Ia.
An olefin Yi can be a C 2 -Ci 2 -, preferably C 2 -Ce- and particularly preferably C 2 -C 4 - olefin. Examples are propene, but-1-ene and in particular ethylene. The diene can contain from 5 to 12 and preferably from 5 to 8 carbon atoms and be an open-chain, cyclic or polycyclic diene. The two olefin groups of the diene are preferably connected by one or two CH 2 groups. Examples are 1 ,4-pentadiene, cyclopentadiene, 1 ,5- hexadiene, 1 ,4-cyclohexadiene, 1 ,4- or 1 ,5-heptadiene, 1 ,4- or 1 ,5-cycloheptadiene, 1 ,4- or 1 ,5-octadiene, 1 ,4- or 1 ,5-cyclooctadiene and norbornadiene. Y is preferably two ethylene molecules or 1 ,5-hexadiene, 1 ,5-cyclooctadiene or norbornadiene.
In formula VIII, Z is preferably Cl or Br. Examples of Ei are BF 4 " , CIO 4 " , CF3SO3 " , CH 3 SO 3 " , HSO 4 " , B(phenyl) 4 " , B[bis(3,5-trifluoromethyl)phenyl] 4 " , PF 6 " , SbCI 6 " , AsF 6 " or SbF 6 " .
The metal complexes of the invention are prepared by methods known from the literature (see also US-A-5,371 ,256, US-A-5,446,844, US-A-5,583,241 and E. Jacobsen, A. Pfaltz, H. Yamamoto (Eds.), Comprehensive Asymmetric Catalysis I to III, Springer Verlag, Berlin, 1999, and references cited therein).
The metal complexes of the invention are homogeneous catalysts or catalyst precursors which can be activated under the reaction conditions and can be used for asymmetric addition reactions on prochiral, unsaturated, organic compounds.
The metal complexes can, for example, be used for asymmetric hydrogenation (addition of hydrogen) of prochiral compounds having carbon-carbon or carbon-hetero- atom double bonds. Such hydrogenations using soluble homogeneous metal complexes are described, for example, in Pure and Appl. Chem., Vol. 68, No. 1 , pages 131-138, (1996). Preferred unsaturated compounds for the hydrogenation contain the groups C=C, C=N and/or C=O. According to the invention, complexes of ruthenium, rhodium and iridium are preferably used for the hydrogenation.
The invention further provides for the use of the metal complexes of the invention as homogeneous catalysts for the preparation of chiral organic compounds, preferably for the asymmetric addition of hydrogen onto a carbon-carbon or carbon-heteroatom double bond in prochiral organic compounds.
A further aspect of the invention is a process for preparing chiral organic compounds by asymmetric addition of hydrogen onto a carbon-carbon or carbon-heteroatom double bond in prochiral organic compounds in the presence of a catalyst, which is characterized in that the addition reaction is carried out in the presence of catalytic amounts of at least one metal complex according to the invention.
Preferred prochiral, unsaturated compounds to be hydrogenated can contain one or more, identical or different groups C=C, C=N and/or C=O in open-chain or cyclic organic compounds, with the groups C=C, C=N and/or C=O being able to be part of a ring system or being exocyclic groups. The prochiral unsaturated compounds can be alkenes, cycloalkenes, heterocycloalkenes or open-chain or cyclic ketones, α,β- diketones, α- or β-ketocarboxylic acids or their, α,β-ketoacetals or -ketals, esters and amides, ketimines and kethydrazones.
Some examples of unsaturated organic compounds are acetophenone, 4-methoxy- acetophenone, 4-trifluoromethylacetophenone, 4-nitroacetophenone, 2-chloro- acetophenone, corresponding unsubstituted or N-substituted acetophenone- benzylimines, unsubstituted or substituted benzocyclohexanone or benzo- cyclopentanone and corresponding imines, imines from the group consisting of unsubstituted or substituted tetrahydroquinoline, tetrahydropyridine and dihydro- pyrrole and unsaturated carboxylic acids, esters, amides and salts such as α- and, if appropriate, β-substituted acrylic acids or crotonic acids. Preferred carboxylic acids are those of the formula
Roi-CH=C(R 02 )-C(0)OH and also their salts, esters and amides, where R01 is Ci-Cε-alkyl, unsubstituted C 3 -C 8 -cycloalkyl or C 3 -C 8 -cycloalkyl substituted by from 1 to 4 Ci-C 6 -alkyl, CrC 6 - alkoxy, Ci-C6-alkoxy-Ci-C4-alkoxy groups or unsubstituted Cε-Cio-aryl or Cε-Cio-aryl substituted by from 1 to 4 Ci-Cε-alkyl, Ci-Cε-alkoxy, Ci-C6-alkoxy-Ci-C4-alkoxy groups and preferably phenyl and R02 is linear or branched Ci-Cε-alkyl (for example isopropyl), unsubstituted or substituted (as defined above) cyclopentyl, cyclohexyl, phenyl or protected amino (for example acetylamino).
The process of the invention can be carried out at low or elevated temperatures for example temperatures of from -20 to 150 0 C, preferably from -10 to 100 0 C and particularly preferably from 10 to 8O 0 C. The optical yields are generally better at relatively low temperature than at higher temperatures.
The process of the invention can be carried out at atmospheric pressure or super- atmospheric pressure. The pressure can be, for example, from 10 5 to 2 x 10 7 Pa (pascal). Hydrogenations can be carried out at atmospheric pressure or at super- atmospheric pressure.
Catalysts are preferably used in amounts of from 0.0001 to 10 mol%, particularly preferably from 0.001 to 10 mol% and very particularly preferably from 0.002 to 5 mol%, based on the compound to be hydrogenated.
The preparation of the ligands and catalysts and also the hydrogenation can be carried out without solvent or in the presence of an inert solvent, with it being possible to use one solvent or a mixture of solvents. Suitable solvents are, for example, aliphatic, cycloaliphatic and aromatic hydrocarbons (pentane, hexane, petroleum ether, cyclohexane, methylcyclohexane, benzene, toluene, xylene), aliphatic halogenated hydrocarbons (methylene chloride, chloroform, dichloroethane and tetrachloroethane), nitriles (acetonitrile, propionitrile, benzonitrile), ethers (diethyl ether, dibutyl ether, t-butyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, dioxane, diethylene glycol monomethyl or monoethyl ether), ketones (acetone, methyl isobutyl ketone), carboxylic esters and lactones (ethyl or methyl acetate, valerolactone), N-substituted lactams (N-methylpyrrolidone), carboxamides (dimethylamide, dimethylformamide), acyclic ureas (dimethylimidazoline), and sulphoxides and sulphones (dimethyl sulphoxide, dimethyl sulphone, tetramethylene sulphoxide, tetramethylene sulphone) and alcohols (methanol, ethanol, propanol, butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether) and water. The solvents can be used either alone or as mixtures of at least two solvents.
The reaction can be carried out in the presence of cocatalysts, for example quaternary ammonium halides (tetrabutylammonium iodide), and/or in the presence of protic acids, for example mineral acids, or inorganic or organic bases (see, for example, US-A-5,371 ,256, US-A-5,446,844 and US-A-5,583,241 and EP-A-O 691 949). The presence of fluorinated alcohols such as 1 ,1 ,1-trifluoroethanol can likewise promote the catalytic reaction.
The metal complexes used as catalysts can be added as separately prepared isolated compounds or can be formed in situ prior to the reaction and then mixed with the substrate to be hydrogenated. It can be advantageous to add additional ligand in the reaction when using isolated metal complexes or to use an excess of ligands in the case of the in situ preparation. The excess can be, for example, from 1 to 6 and preferably from 1 to 2 mol, based on the metal compound used for the preparation.
The process of the invention is generally carried out by placing the catalyst in a reaction vessel and then adding the substrate, if appropriate reaction auxiliaries and the compound to be added on and subsequently starting the reaction. Gaseous compounds to be added on, for example hydrogen or ammonia, are preferably introduced under pressure. The process can be carried out continuously or batchwise in various types of reactor.
The chiral, organic compounds prepared according to the invention are active substances or intermediates for the preparation of such substances, in particular in the field of preparation of favours and fragrances, pharmaceuticals and agro- chemicals.
The following examples illustrate the invention.
Starting materials and abbreviations
1-[(Dimethylamino)eth-1-yl]ferrocene is commercially available. 1-[(Dimethylamino)eth-1-yl]-2-bromoferrocene of the formula
1-Ethyl-2-bromo-3-diphenylphosphinoferrocene of the formula
is prepared as described in the Patent WO2006114438. The compound will hereinafter be referred to as C2.
The reactions are carried out under inert gas (argon).
The reactions and yields are not optimized.
Abbreviations: TMP = 2,2,6,6-tetramethylpiperidine; TBME= tert-butyl methyl ether;
DMF: N,N-dimethylformamide, THF = tetrahydrofuran, MeOH = methanol, EA = ethyl acetate, Me = methyl, Et = ethyl, i-Pr = i-propyl, nbd = norbornadiene,
Cy = cyclohexyl, n-BuLi = n-butyllithium, eq. = equivalent(s).
sec-Phosphino-o-bromobenzenes are prepared as follows: a) 2-Diphenylphosphino-1 -bromobenzene
17.5 ml (35 mmol) of i-propylmagnesium chloride (2.0 M in THF) are added dropwise to a solution of 5 ml (35 mmol) of 2-bromoiodobenzene in 25 ml of THF while stirring at from -30 0 C to -35°C. The temperature is maintained and the reaction mixture is stirred for a further 1 hour. 9.3 g (42 mmol) of diphenylphosphine chloride are then added slowly, the mixture is stirred for a further 30 minutes and the cooling is then removed. After stirring at room temperature for 1 hour, 20 ml of water are added, the mixture is extracted with ethyl acetate, the organic phase is washed with saturated aqueous NaHCO3 and NaCI solution and dried over sodium sulphate. Distilling off the solvent gives a colourless oil which becomes solid on addition of 100 ml of ethanol. Filtration and washing with a little ethanol gives the desired product as a white powder in a yield of 90%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.38-7.30 (m, 5H), 7.06-7.02 (m, 6H), 6.91-6.86 (m, 1 H), 6.79-6.73 (m, 1 H), 6.71-6.65 (m, 1 H). 31 P-NMR (C 6 D 6 , 121 MHz): -3.79 (s).
b) 2-Di(para-trifluoromethylphenyl)phosphino-1 -bromobenzene The compound is prepared by a method analogous to method a). bis(p-Trifluoromethylphenyl)phosphine chloride is used in the place of diphenylphosphine chloride. The title compound is obtained as a white powder in a yield of 90%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.23-7.18 (m, 1 H),
7.10-7.01 (m, 4H), 6.93-6.84 (m, 4H), 6.67-6.54 (m, 2H), 6.48-6.43 (m, 1 H). 31 P- NMR (C 6 D 6 , 121 MHz): -4.83 (s).
c) 2-Diethylphosphino-1 -bromobenzene
The compound is prepared by a method analogous to method a). Diethylphosphine chloride is used in place of diphenylphosphine chloride. The title compound is obtained as a colourless oil in a yield of 63%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.43-7.38 (m, 1 H), 7.06-7.01 (m, 1 H), 6.96-6.90 (m, 1 H), 6.75-6.68 (m, 1 H), 1.62- 1.38 (m, 4H), 0.99-0.86 (m, 6H). 31 P-NMR (C 6 D 6 , 121 MHz): -14.5 (s).
A) Preparation of 2-halo-3-sec-phosphinoferrocenes
Example A1 : 1 -[(Dimethylamino)eth-I -yl]-2-bromo-3(dicyclohexylphosphino)- ferrocene (A1) of the formula
11.2 ml (66.9 mmol, 3.0 eq.) of 2,2-6,6-tetramethylpiperidine (TMP, 98%) are dissolved in 100 ml of absolute THF and cooled to 0 0 C. 40.0 ml (64.7 mmol, 2.9 eq.) of n-butyllithium solution (1.6 M in hexane) are added dropwise. The mixture is subsequently stirred at 0 0 C for one hour (solution A). 7.46 g (22.3 mmol, 1.0 eq.) of compound C1 are dissolved in 60 ml of absolute THF and cooled to -60 0 C (solution B). Solution A is then added dropwise to solution B over a period of 30 minutes and the mixture is then stirred for 1.5 hours, with the temperature being allowed to rise to -40°C. The reaction mixture is cooled to -78°C and 6.00 ml (26.9 mmol, 1.2 equivalents) of dicyclohexylphosphine chloride are added. After stirring at -78°C for a further 2.5 hours, 150 ml of water are added and the organic phase is then isolated. The aqueous phase is acidified with saturated, aqueous ammonium chloride solution and extracted with 100 ml of TBME. The combined organic phases are dried over sodium sulphate and freed of the solvent. The brown oil obtained is purified by chromatography [silica gel, eluent = acetone:heptane (1 :2)]. This gives 9.75 g (82%) of the title compound as a brown oil. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 4.05
(S, 5H, cp), 2.16 (s, 6H, N(CHs) 2 ), 1.35 (d, 3H, C(NMe 2 )CH 3 ). 31 P-NMR (C 6 D 6 , 121 MHz): -9.3 (S).
Example A2: 1 -[(Dimethylamino)eth-I -yl]-2-bromo-3(diphenylphosphino)ferrocene (A2) of the formula
Compound A2 is prepared by a method analogous to Example A1. Diphenylphosphine chloride is used in place of dicyclohexylphosphine chloride. The crude product is purified by chromatography (silica gel 60; eluent = EA containing 2% of triethylamine). The title compound is obtained as an orange solid in a yield of 73%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.62 (m, 2H), 7.65 (m, 2H), 7.11- 6.99 (m, 6H), 4.03 (s, 5H), 3.96 (m, 1 H), 3.90 (q, 1 H), 3.65 (m, 1 H), 2.19 (s, 6H), 1.31 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -18.4 (s).
Example A3: 1 -[(Dimethylamino)eth-I -yl]-2-bromo-3-(di-ortho-anisylphosphino)- ferrocene (A3) of the formula
Compound A3 is prepared by a method analogous to Example A1. Di-ortho-anisyl- phosphine chloride is used in place of dicyclohexylphosphine chloride. The crude product is purified firstly by chromatography (silica gel 60; eluent = toluene containing 1 % of triethylamine) and subsequently by recrystallization from MeOH. The title compound is obtained as a yellow solid in a yield of 64%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.36-6.36 (various m, 8 aromatic H), 4.17 (s, 5H, cp), 4.02 (m, 1 H), 3.95 (m, 1 H), 3.47 (s, 3H), 3.11 (s, 3H), 2.24 (s, 6H, N(CHs) 2 ), 1.37 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -44.2 (s).
Example A4: 1 -[(Dimethylamino)eth-I -yl]-2-bromo-3-(di(3,5-dimethyl-4-methoxy- phenyl)phosphino)ferrocene (A4) of the formula
Compound A4 is prepared by a method analogous to Example A1. Di(3,5-dimethyl- 4-methoxyphenyl)phosphine chloride is used in place of dicyclohexylphosphine chloride. The crude product is purified by chromatography (silica gel 60; eluent = acetone). The title compound is obtained as a yellow-orange solid in a yield of 87%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.54 (s, 1 H), 7.52 (s, 1 H), 7.20 (s, 1 H), 7.17 (s, 1 H), 4.11 (s, 5H), 4.05 (m, 1 H), 3.95 (q, 1 H), 3.86 (m, 1 H), 3.31 (s, 3H), 3.27 (s, 3H), 2.25 (s, 6H), 2.13 (s, 6H), 2.12 (s, 6H), 1.38 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -20.6 (S).
B) Preparation of 2-formyl-3-sec-phosphinoferrocene
Example B1 : 1 -[(Dimethylamino)eth-I -yl]-2-formyl-3-(diphenylphosphino)ferrocene (B1 ) of the formula
2.8 ml (4.6 mmol) of n-BuLi (1.6 M solution in hexane) are added dropwise to a solution of 2.0 g (3.84 mmol) of compound A2 in 30 ml of TBME at 0 0 C while stirring and the reaction mixture is stirred at this temperature for another one hour. 0.63 ml (7.6 mmol) of DMF is then slowly added dropwise over a period of 30 minutes. The mixture is stirred at 0 0 C for another 30 minutes and the cooling bath is then removed and the temperature is allowed to rise to room temperature. The reaction mixture is admixed with 20 ml of water and extracted with ethyl acetate. The organic phases
are combined, washed with saturated aqueous NaCI, dried over sodium sulphate and evaporated to dryness on a rotary evaporator. Purification by chromatography (silica gel 60; eluent = EA/heptane 1 :1 containing 1 % of triethylamine) gives the title compound B1 as a red-orange foam in a yield of > 95%. 1 H-NMR (CeD 6 , 300 MHz), characteristic signals: 10.47 (d, 1 H), 7.60-6.98 (various m, 10 aromatic H), 4.24 (q, 1 H), 4.15 (m, 1 H), 3.94 (s, 5H), 3.82 (m, 1 H), 2.09 (s, 6H), 1.18 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -19.1 (s).
Example B2: 1 -[(Dimethylamino)eth-I -yl]-2-formyl-3-(di-ortho-anisylphosphino)- ferrocene (B2) of the formula
Compound B2 is prepared by a method analogous to Example B1 starting out from compound A3. Purification by chromatography (silica gel 60; eluent = EA containing 1 % of triethylamine) gives the title compound as a red-orange foam in a yield of > 95%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 10.58 (d, 1 H), 7.32-6.36
(various m, 8 aromatic H), 4.44 (q, 1 H), 4.25 (m, 1 H), 4.09 (s, 5H, cp), 3.95 (m, 1 H), 3 3..4433 ((ss,, 33HH)),, 33..1122 ((ss,, 3H), 2.18 (s, 6H, N(CHs) 2 ), 1.28 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -45.2 (S).
Example B3: 1 -[(Dimethylamino)eth-I -yl]-2-formyl-3-(dicyclohexylphosphino)- ferrocene (B3) of the formula
Compound B3 is prepared by a method analogous to Example B1 starting out from compound A1. Purification by chromatography (silica gel 60; eluent = EA/heptane 1 :1 containing 1 % of triethylamine) gives the title compound as a red-orange foam in a
yield of 56%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 10.21 (d, 1 H), 4.65 (m, 1 H), 4.41 (m, 1 H), 4.39 (q, 1 H), 4.13 (s, 5H, cp), 2.04 (s, 6H, N(CHs) 2 ), 1.45 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -16.1 (s).
Example B4: 1 -[(Dimethylamino)eth-I -yl]-2-formyl-3-(bis(3,5-dimethyl-4-methoxy- phenyl) phosphino)ferrocene (B4) of the formula
Compound B4 is prepared by a method analogous to Example B1 starting out from compound A4. 3 equivalents of DMF are added per lithiated equivalent of the compound A4. The title compound is obtained in virtually quantitative yield as a red- orange solid foam which is still contaminated with a little debrominated material. The product is used further without purification. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 10.55 (d, 1 H), 7.48 (s, 1 H), 7.45 (s, 1 H), 7.18 (s, 1 H), 7.16 (s, 1 H), 4.36 (q, 1 H), 4.26 (m, 1 H), 4.04 (m, 1 H), 4.03 (s, 5H), 3.31 (s, 3H), 3.25 (s, 3H), 2.18-2.07 (m, 18 H), 1.26 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -21.6 (s).
Example B5: 1-Ethyl-2-formyl-3(diphenylphosphino)ferrocene (B5) of the formula
Compound B5 is prepared by a method analogous to Example B4 starting out from compound C2. 3 equivalents of DMF are added per lithiated equivalent of the compound C2. The title compound is obtained in virtually quantitative yield as a red solid foam. The product is used further without purification. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 10.66 (d, 1 H), 7.59-6.95 (various m, 10 H), 4.19
(m, 1 H), 3.89 (s, 5H), 3.80 (m, 1 H), 2.85 (m, 1 H), 2.54 (m, 1 H), 1.14 (t, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -21.4 (S).
C) Preparation of ferrocenediphosphines
Example C1 : Preparation of
1 ml (1.6 mmol) of n-BuLi (1.6 molar in hexane) is added dropwise to a solution of 0.532 g (1.6 mmol) of the compound 2-diphenylphosphino-1-bromobenzene in a mixture of 5 ml of THF and 5 ml of TBME at a temperature of -70 0 C while stirring. The red reaction solution is stirred at a temperature of from -70 0 C to -40°C for 1 hour. This solution is then slowly added to a solution of 0.54 g (1.2 mmol) of the compound B1 in 5 ml of TBME and the mixture stirred further at -70 0 C. After 15 minutes, the cooling is removed and the mixture is stirred at room temperature for another 1.5 hours. The reaction mixture is admixed with 20 ml of water, the organic phase is washed with saturated, aqueous NaCI, dried over sodium sulphate and the solvent is distilled off on a rotary evaporator. An NMR spectrum of the crude product shows that virtually only one of two possible diastereomers has been formed. Purification by chromatography (silica gel; eluent = EA/heptane 1 :2 containing 1 % of triethylamine) gives the title compound in the form of a pure diastereomer as an orange foam in a yield of 80%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.81-6.58 (various m, 24 aromatic H), 4.46 (q, 1 H), 4.22 (m, 1 H), 4.09 (m, 1 H), 4.04 (s, 5H), 1.85 (s, 6H), 0.96 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -15.9 (d), -24.6 (d).
Example C1.1 : Preparation of the other epimer of C1 (other configuration on the alcohol carbon)
2.8 ml (4.6 mmol) of n-BuLi (1.6 M solution in hexane) are added dropwise to a solution of 0.96 g (1.84 mmol) of compound A2 in 30 ml of TBME at 0°C while stirring
and the reaction mixture is stirred at this temperature for another one hour. A solution of 1 equivalent of 2-(diphenylphosphino)benzaldehyde (commercially available) in 5 ml of THF is then added dropwise. The mixture is stirred at 0 0 C for another 30 minutes, the cooling bath is then removed and the temperature is allowed to rise to room temperature. The reaction mixture is admixed with 20 ml of water and extracted with ethyl acetate. The organic phases are combined, dried over sodium sulphate and evaporated to dryness on a rotary evaporator. An NMR spectrum of the crude product shows that predominantly the other epimer has been formed (ratio of C1 to C1.1 is about 1 :4). Column chromatography (silica gel 60; eluent = EA/heptane 1 :1 containing 1 % of triethylamine) gives small amounts of the compound C1 in the first fraction and the title compound C1.1 as an orange-yellow foam in the 2nd fraction (yield: 68%). 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.65-6.76 (various m, 24 aromatic H), 4.21 (q, 1 H), 4.21 (m, 1 H), 4.10 (m, 1 H), 3.88 (s, 5H), 1.90 (s, 6H), 1.03 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -12.7 (d), -22.4 (d).
Example C1.2: Preparation of
A solution of 175 mg (0.24 mmol) of the compound C1 in 3 ml of THF is added drop- wise to a suspension of 42 mg (0.36 mmol) of potassium hydride in 1 ml of THF at 0-5 0 C. The temperature is subsequently increased to 50 0 C and the mixture is stirred for 30 minutes. After cooling to 0-5°C, 18 microlitres (0.29 mmol) of methyl iodide are added. The cooling is removed and the mixture is stirred at room temperature for another 30 minutes. The yellow suspension is admixed with water. After extraction with TBME, the organic phase is dried over sodium sulphate and freed of the solvent. Purification by chromatography (silica gel; eluent = ethyl acetate containing 1 % of NEtβ) gives the title compound as a solid yellow foam in a yield of 92%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 9.30 (m. 1 H), 7.75-6.84 (various m, 24H),
4.76 (m, 1 H), 4.20 (m, 1 H), 3.94 (m, 1 H), 3.88 (s, 5H), 3.01 (s, 3H), 2.32 (s, 6H), 1.21 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -17.3 (d), -18.7 (d).
Example C2: Preparation of
Compound C2 is prepared by a method analogous to Example C1 starting out from compound B1 and 2-di(para-trifluoromethylphenyl)phosphino-1-bromobenzene. According to NMR of the crude product, only one of the two possible diastereomers is formed. Purification by chromatography (silica gel; eluent = EA/heptane 1 :1.5) gives the title compound in the form of a pure diastereomer as a yellow solid foam in a yield of 89%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.69-6.58 (various m, 22H), 4.39 (q, 1 H), 4.22 (m, 1 H), 4.11 (m, 1 H) 4.02 (s, 5H), 1.81 (s, 6H), 0.92 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -15.2 (d), -24.5 (d).
Example C3: Preparation of
Compound C3 is prepared by a method analogous to Example C1 starting out from compound B1 and 2-diethylphosphino-1-bromobenzene. According to NMR of the crude product, only one of the two possible diastereomers is formed (> 95%). Purification by chromatography (silica gel; eluent = EA/heptane 1 :1 containing 1 % of NEt 3 ) gives the title compound in the form of a pure diastereomer as a yellow solid foam in a yield of 81%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.77-6.62 (various m, 14H), 4.57 (q, 1 H), 4.21 (m, 1 H), 4.08 (s, 5H), 4.04 (m, 1 H), 1.93 (s, 6H),
1.92-1.76 (m, 4H), 1.40-1.09 (m, 6H), 0.99 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -24.2 (d), -31.5 (d).
Example C4: Preparation of
Compound C4 is prepared by a method analogous to Example C1 starting out from compound B2 and 2-diphenylphosphino-1-bromobenzene. Purification by chromatography (silica gel; eluent = EA/heptane 1 :2 to 1 :1 containing 1 % of triethylamine) gives the title compound in the form of a pure diastereomer as an orange foam in a yield of 56%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.92-6.17 (various m, 22 aromatic H), 4.52 (q, 1 H), 4.28 (m, 1 H), 4.25 (m, 1 H), 4.17 (s, 5H), 3.52 (s, 3H), 2.97 (s, 3H), 1.90 (s, 6H), 1.00 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -15.9 (d), -52.2 (d).
Example C5: Preparation of
0.9 ml (1.4 mmol) of n-BuLi (1.6 molar in hexane) is added dropwise to a solution of 1.7 g (5 mmol) of 2-diphenylphosphino-1-bromobenzene in a mixture of 20 ml of THF and 30 ml of TBME at a temperature of -70 0 C while stirring. The red reaction solution is stirred at a temperature of from -70 0 C to -40 0 C for 1 hour. This solution is then slowly added to a solution of 2 g (4.2 mmol) of the compound B3 in 30 ml of TBME and the mixture is stirred at -70 0 C. After 1 hour, the temperature is allowed to rise to -50 0 C. The reaction mixture is admixed with 20 ml of water, the organic phase is washed with saturated aqueous NaCI, dried over sodium sulphate and the solvent is distilled off on a rotary evaporator. An NMR spectrum of the crude product shows
that virtually only one of two possible diastereomers has been formed. Purification by chromatography (silica gel; eluent = acetone/toluene 1 :10) gives the title compound in the form of a pure diastereomer as an orange foam in a yield of 55%. 1 H-NMR (CeD 6 , 300 MHz), characteristic signals: 7.86-7.04 (diverse m, 14 aromatic H), 5.67 (broad s, 1 H), 4.58 (q, 1 H), 4.33 (m, 1 H), 4.31 (s, 5H), 4.24 (m, 1 H), 1.96 (s, 6H), 1.11 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -11.0 (d), -16.5 (d).
Example C6: Preparation of
Compound C6 is prepared by a method analogous to Example C5 starting out from the compounds B3 and 2-di(para-trifluoromethylphenyl)phosphino-1-bromobenzene. Purification by chromatography (silica gel; eluent = EA/heptane 1 :20 containing 1 % of triethylamine) gives the title compound as pure diastereomer as an orange foam in a yield of 75%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.65-7.05 (various m, 12 aromatic H), 6.22 (broad s, 1 H), 4.51 (q, 1 H), 4.32 (m, 1 H), 4.31 (s, 5H), 4.22 (m, 1 H), 1.91 (s, 6H), 1.06 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -11.3 (d), -15.6 (d).
Example C7: Preparation of the compound
Compound C7 is prepared by a method analogous to Example C1 starting out from compound B4 and 2-diphenylphosphino-1-bromobenzene. According to NMR of the crude product, only one of the two possible diastereomers is formed (> 95%). Purification by chromatography (silica gel; eluent = EA/heptane 1 :5 containing 0.5% of triethylamine) gives the title compound in the form of a pure diastereomer as a yellow
solid foam in a yield of 51%. 1 H-NMR (CeD 6 , 300 MHz), characteristic signals: 7.90-6.57 (various m, 18H), 4.52 (m, 1 H), 4.27 (s, 2H), 4.14 (s, 5H), 3.31 (s, 3H), 3.29 (s, 3H), 2.18 (s, 6H), 2.12 (s, 6H), 1.90 (s, 6H), 0.97 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -16.6 (d), -26.2 (d).
Example C8: Preparation of the compound
Compound C8 is prepared by a method analogous to Example C1 starting out from compound B4 and 2-di(para-trifluoromethylphenyl)phosphino-1-bromobenzene. According to NMR of the crude product, only one of the two possible diastereomers is formed (> 95%). Purification by chromatography (silica gel; eluent = EA/heptane 1 :5 containing 0.5% of triethylamine) gives the title compound in the form of a pure diastereomer as a yellow solid foam in a yield of 50%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.79-6.56 (various m, 17 H), 4.45 (q, 1 H), 4.31-4.27 (m, 2H), 4.13 (s, 5H), 3.291 (s, 3H), 3.288 (s, 3H), 2.14 (s, 6H), 2.02 (s, 6H), 1.87 (s, 6H), 0.95 (d, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -16.0 (d), -26.1 (d).
Example C9: Preparation of the compounds
Compound C9 is prepared by a method analogous to Example C1 starting out from compound B5. According to NMR of the crude product, a mixture of the two possible diastereomers in a ratio of about 2:8 is formed. The two diastereomers can be separated by means of column chromatography (silica gel; eluent = EA/heptane1 :25).
The first fraction gives the diastereomer C9b which is formed in only small amounts. It is isolated as an orange solid in a yield of 15%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.63-6.70 (various m, 24 aromatic H), 4.23 (m, 1 H), 4.04 (s, 5H), 3.88 (m, 1 H), 2.96 - 2.68 (m, 2H), 1.10 (t, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -16.0 (d), -22.4 (d).
The second fraction gives the main diastereomer C9a as an orange solid in a yield of 75%. 1 H-NMR (C 6 D 6 , 300 MHz), characteristic signals: 7.60-6.60 (various m, 24 aromatic H), 4.46 (m, 1 H), 4.16 (m, 1 H), 4.03 (m, 1 H), 3.96 (s, 5H), 2.26 (q, 2H), 0.85 (t, 3H). 31 P-NMR (C 6 D 6 , 121 MHz): -14.0 (d), -21.6 (d).
D) Preparation of metal complexes
Procedure: about 10 mg of ligand together with 0.95 molar equivalent of [Rh(norbornadiene) 2 ]BF 4 are dissolved in 0.7 ml of CD 3 OD under an argon atmosphere. The red solution is transferred under argon to an NMR tube and examined by means Of 31 P-NMR.
Example D1 : Rhodium complex with the ligand C1
31 P-NMR (CD 3 OD, 121 MHz): 24.4 (d of d, J Rh-P = 156 Hz), 16.7 (d of d, J Rh-P = 158 Hz).
Example D2: Rhodium complex with the ligand C1.1
31 P-NMR (CD 3 OD, 121 MHz): 20.4 (d of d, J Rh-P = 152 Hz), 16.9 (d of d, J Rh-P = 152 Hz).
E) Use examples
All work was carried out under argon using degassed solvents.
Examples E1-E23: Hydrogenations
4.73 mg (0.0127 mmol) of [Rh(norbornadiene) 2 ]BF 4 and (0.0133 mmol) of ligand C1 (ratio of ligand to metal = 1.05) are stirred in 2 ml of methanol for 10 minutes. A solution of 550 mg (2.5 mmol) of methyl acetamidocinnamate (MAC) in 4 ml of methanol is added to this solution, followed by the amount of methanol (4 ml)
required for the substance concentration to be 0.25 M. The argon is taken off by means of vacuum and the vessel is connected to a hydrogen supply (1 bar). The hydrogenation is started by switching on the stirrer. After 1 hour, the stirrer is switched off and the solution is blanketed with argon again. Conversion and enantiomeric excess (ee) are determined by gas chromatography using a chiral column (Lipodex E): the conversion is quantitative and the optical yield ee (entantiomeric excess) is 98%.
The hydrogenations of further substrates shown in Table 1 below are carried out in an analogous way. The hydrogenations using a relatively high hydrogen pressure are carried out in a steel autoclave. The reaction solutions are injected into the argon- flushed autoclave by means of a hollow needle under a countercurrent of argon. The results are reported in Table 2.
Table 1 : Substrates
Abbreviations: ee = enantiomeric excess, GC = gas chromatography, HPLC = high- pressure liquid chromatography
Table 2: Hydrogenation results
Additions: 1) 1 N HCI (1.2% by volume); 2) 2 equivalents of tetrabutylammonium iodide/mole of Ir and CF 3 COOH (0.6% by volume); 3) reaction in presence of 10% CF 3 -CH 2 -OH (by volume). In Example No. 11 , the temperature is 80 0 C, otherwise 25°C.
Abbreviations used here:
[S] is molar substrate concentration; S/C is substrate/catalyst ratio; t is hydrogenation time; SoIv. is solvent (MeOH = methanol; EtOH = ethanol; ToI = toluene; THF = tetrahydrofuran; DCE = 1 ,2-dichloroethane); metal: metal precursors used in the hydrogenations: Rh a) = [Rh(norbornadiene) 2 ]BF 4 ; Rh b) = [Rh(cyclooctadiene)CI] 2 ; lr c) = [lr(cyclooctadiene)CI]2; Ru d) = [Rul2(p-cymene)]2 ; C = conversion; Conf. = configuration. P = hydrogen pressure (bar).
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