Method for the asymmetric hydrogenation of .alpha.-ketocarbonyl compounds to optically active .alpha.-hydroxycarbonyl compounds

A method for the asymmetric hydrogenation of .alpha.-ketocarbonyl compounds selected from the group consisting of .alpha.-ketocarboxylic acid esters, and .alpha.-ketolactones to the corresponding optically active .alpha.-hydroxycarbonyl compounds in the presence of chiral platinum-metal diphosphine complexes as catalyst;

• the improvement wherein the chiral platinum group-metal complexes are chiral iridium complexes which contain an optically active 1,2-diphosphine ligand of the general Formula Ia, Ib or Ic, ##STR3## in which R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are the same or different and signify C.sub.1 to C.sub.8 alkyl, which can be linear or branched, a cyclohexylmethyl, C.sub.5 to C.sub.7 cycloalkyl, which can have one or two C.sub.1 to C.sub.4 alkyl substituents, benzyl or phenyl, the aromatic ring of which can contain C.sub.1 to C.sub.4 alkyl-, C.sub.1 to C.sub.4 alkoxy-, di-(C.sub.1 to C.sub.4) alkylamino- or C.sub.1 to C.sub.4 alkyloxycarbonyl substituents or R.sup.1 R.sup.2 and/or R.sup.3 R.sup.4 represent an orthobiphenylene group,
• X stands for oxygen, the group NR.sup.13, CR.sup.14 R.sup.15, -CR.sup.14 =CR.sup.15 - or -CHR.sup.14 -CHR.sup.15 -, in which R.sup.13 signifies hydrogen, C.sub.1 to C.sub.6 alkyl, C.sub.5 to C.sub.7 cycloalkyl, benzyl or an acyl group from the series -COalkyl, -COaryl, -COOalkyl, -COOaryl, -SO.sub.2 aryl, -P(O)aryl.sub.2, in which the alkyl group contains 1 to 4 carbon atoms and aryl stands for phenyl or naphthyl and can contain one or two C.sub.1 to C.sub.4 alkyl-, C.sub.1 to C.sub.4 alkoxy-, di-(C.sub.1 to C.sub.4) alkylamino-, C.sub.1 to C.sub.4 alkoxycarbonyl substituents and R.sup.14 and R.sup.15 are the same or different and signify hydrogen, C.sub.1 to C.sub.4 alkyl or phenyl,
• R.sup.5 and R.sup.6 are the same or different and signify hydrogen, C.sub.1 to C.sub.4 alkyl or phenyl,
• R.sup.7 and R.sup.8 are the same or different and signify hydrogen, phenyl, C.sub.1 to C.sub.4 alkoxycarbonyl or C.sub.1 to C.sub.4 alkyl, R.sup.9 and R.sup.10 constitute a double bond in common or signify hydrogen,
• R.sup.11 and R.sup.12 are the same or different and signify C.sub.1 to C.sub.6 alkyl, benzyl or phenyl, one of the groups R.sup.11 and R.sup.12 can also be hydrogen or, under the condition that at least one phosphorus atom or one of the groups R.sup.1 to R.sup.4 is chiral, R.sup.11 and R.sup.12 also stand for hydrogen,
• and wherein the hydrogenation is carried out in the presence of a co-catalyst from the group of cyclic dicarboxylic acid imides of the general Formula II ##STR4## in which Y signifies an ethylene- or tri- or tetramethylene group, which may be substitute with a phenyl group or one or two C.sub.1 to C.sub.8 alkyl substituents, or Y is a vinylene- or ortho-arylene group, which can contain one or two substituents from the group (C.sub.1 to C.sub.4) alkyl, (C.sub.1 to C.sub.4) alkoxy, (C.sub.1 to C.sub.4) alkoxycarbonyl, di-(C.sub.1 to C.sub.4) alkylamino.