Oxotitanium complex, asymmetric hydrogenation catalyst comprising the complex, and process for producing .beta.-hydroxy ketone or .alpha.-hydroxy carboxylic acid ester using the complex

A process for producing an .alpha.-hydroxy carboxylic acid ester represented by general formula (V):

• ##STR16## wherein R.sup.6 represents a hydrogen atom or a lower alkyl group and R.sup.7 represents a lower alkyl group, a phenyl group, or a cycloalkyl group, provided that R.sup.6 and R.sup.7 may be bonded to each other to form a hydrocarbon ring in cooperation with the carbon atoms to which R.sup.6 and R.sup.7 are bonded, and R.sup.8 represents a lower alkyl group, or
• for producing a .beta.-hydroxy ketone represented by general formula (VIII):
• ##STR17## wherein R.sup.9 and R.sup.10 may be the same or different and each represents a hydrogen atom or a lower alkyl group, R.sup.11 represents a lower alkyl group, a lower alkoxy group, a phenyl group, a phenoxy group, or a lower alkylthio group, and R.sup.15 represents a lower alkyl group, a lower alkoxymethyl group, a phenyl group, a substituted phenyl group, a benzyloxymethyl group, or a lower alkoxycarbonyl group, which process comprises
• (A) reacting an olefin compound represented by general formula (III):
• ##STR18## wherein R.sup.6 and R.sup.7 have the same meanings as defined above, with a glyoxylate compound represented by general formula (IV):
• ##STR19## wherein R.sup.8 has the same meaning as defined above, in the presence of an oxotitanium complex to thereby produce the .alpha.-hydroxy carboxylic acid ester, or
• (B) reacting a silyl enol ether compound represented by general formula (VI):
• ##STR20## wherein R.sup.9, R.sup.10, and R.sup.11 have the same meanings as defined above, and R.sup.12, R.sup.13, and R.sup.14 may be the same or different and each represents a lower alkyl group or a phenyl group, with an aldehyde compound represented by general formula (VII):
• R.sup.15 CHO (VII)
• wherein R.sup.15 has the same meaning as defined above, in the presence of an oxotitanium complex to thereby produce the .beta.-hydroxy ketone,
• wherein said oxotitanium complex is represented by general formula (I):
• ##STR21## wherein R.sup.1 and R.sup.2 may be the same or different and each represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a halogen atom, a phenyl group, a substituted phenyl group, a trialkylsilyl group, a monoalkyldiphenylsilyl group, a dialkylmonophenylsilyl group, a triphenylsilyl group, a substituted triphenylsilyl group, or a lower alkoxycarbonyl group, provided that R.sup.1 and R.sup.2 may be bonded to each other to form a hydrocarbon ring or a substituted hydrocarbon ring in cooperation with the carbon atoms to which R.sup.1 and R.sup.2 are bonded;
• R.sup.3 and R.sup.4 may be the same or different and each represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a benzoyl group, a benzenesulfonyl group, or a halogen atom, provided that R.sup.3 and R.sup.4 may be bonded to each other to form a hydrocarbon ring or a substituted hydrocarbon ring in cooperation with the carbon atoms to which R.sup.3 and R.sup.4 are bonded;
• and n is 1 or 2.