The present invention relates to a process for the preparation of an optically active carbonyl compound by asymmetric hydrogenation of a prochiral ,-unsaturated carbonyl compound with hydrogen in the presence of at least one optically active transition metal catalyst that is soluble in the reaction mixture and which has rhodium as catalytically active transition metal and a chiral, bidentate bisphosphine ligand, wherein the reaction mixture during the hydrogenation of the prochiral ,-unsaturated carbonyl compound additionally comprises at least one compound of the general formula (I):

##STR00001## in which R.sup.1, R.sup.2: are identical or different and are C.sub.6- to C.sub.10-aryl which is unsubstituted or carries one or more, e.g. 1, 2, 3, 4 or 5, substituents which are selected from C.sub.1- to C.sub.6-alkyl, C.sub.3- to C.sub.6-cycloalkyl, C.sub.6- to C.sub.10-aryl, C.sub.1- to C.sub.6-alkoxy and amino; Z is a group CHR.sup.3R.sup.4 or aryl which is unsubstituted or carries one or more, e.g. 1, 2, 3, 4 or 5, substituents which are selected from C.sub.1- to C.sub.6-alkyl, C.sub.3- to C.sub.6-cycloalkyl, C.sub.6- to C.sub.10-aryl, C.sub.1- to C.sub.6-alkoxy and amino, wherein R.sup.3 and R.sup.4 are as defined in the claims and the description.

The present invention discloses a metal complex catalyst, its preparing method and its application in preparing D,L-menthol, the metal complex catalyst includes weight percent elements as follows: 70-85% of Ni, 8-10% of Al, 5-10% of V, and 2-10% of Co. When this metal complex catalyst is applied in preparing D,L-menthol through thymol hydrogenation, it has the characteristics of high reaction activity and quick racemization of chiral compound. Meanwhile, a certain kind of alkali added in isomerization is the key to reducing light constituent byproduct. The whole process comes in good reaction selectivity, simple preparing technology, low production cost, and environment-friendly synthetic route.

The present invention discloses a metal complex catalyst, its preparing method and its application in preparing D,L-menthol, the metal complex catalyst includes weight percent elements as follows: 70-85% of Ni, 8-10% of Al, 5-10% of V, and 2-10% of Co. When this metal complex catalyst is applied in preparing D,L-menthol through thymol hydrogenation, it has the characteristics of high reaction activity and quick racemization of chiral compound. Meanwhile, a certain kind of alkali added in isomerization is the key to reducing light constituent byproduct. The whole process comes in good reaction selectivity, simple preparing technology, low production cost, and environment-friendly synthetic route.

The present invention discloses a metal complex catalyst, its preparing method and its application in preparing D,L-menthol, the metal complex catalyst includes weight percent elements as follows: 70-85% of Ni, 8-10% of Al, 5-10% of V, and 2-10% of Co. When this metal complex catalyst is applied in preparing D,L-menthol through thymol hydrogenation, it has the characteristics of high reaction activity and quick racemization of chiral compound. Meanwhile, a certain kind of alkali added in isomerization is the key to reducing light constituent byproduct. The whole process comes in good reaction selectivity, simple preparing technology, low production cost, and environment-friendly synthetic route.

The present invention relates to a particularly economic overall method for producing menthol, specifically for producing optically active, essentially enantiomerically and diastereomerically pure L-menthol and racemic menthol, starting from the starting material citral which is available inexpensively on an industrial scale. The method has the following steps a.1) catalytic hydrogenation of neral and/or geranial to give citronellal, b.1) cyclization of citronellal to isopulegol in the presence of an acidic catalyst, c.1) purification of isopulegol by crystallization and d.1) catalytic hydrogenation of isopulegol to give menthol.

The present invention relates to a particularly economic overall method for producing menthol, specifically for producing optically active, essentially enantiomerically and diastereomerically pure L-menthol and racemic menthol, starting from the starting material citral which is available inexpensively on an industrial scale. The method has the following steps a.1) catalytic hydrogenation of neral and/or geranial to give citronellal, b.1) cyclization of citronellal to isopulegol in the presence of an acidic catalyst, c.1) purification of isopulegol by crystallization and d.1) catalytic hydrogenation of isopulegol to give menthol.

The present invention relates to improved processes for the preparation of ruthenium or osmium complexes comprising acetate ligands, in particular, ruthenium complexes.

The present invention relates to improved processes for the preparation of ruthenium or osmium complexes comprising acetate ligands, in particular, ruthenium complexes.

A method of producing an alcohol, comprises reducing an aldehyde or a ketone with a hydridosilatrane. The reducing is carried out with an activator.

A method of producing an alcohol, comprises reducing an aldehyde or a ketone with a hydridosilatrane. The reducing is carried out with an activator.