Abstract: 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.

Abstract: The present invention relates to a process for preparing optically active bisphosphinylalkanes from the correspondingly substituted, racemic 1,2-diols. The optically active bisphosphinylalkanes which can be obtained in this way are suitable as ligands for preparing chiral transition metal catalysts.

Abstract: A process for preparing optically active 2-methylalkan-1-ol of the general formula (III) comprising the following steps: (i) carbonyl-selective reduction of 2-methylalk-2-en-1-al of the general formula (I) to 2-methylalk-2-en-1-ol of the general formula (II), (ii) enantioselective hydrogenation of 2-methylalk-2-en-1-ol to the general formula (iii), (iii) increasing the optical yield of the optically active 2-methylalkan-1-ol (III) obtained in step (ii) by a lipase-catalyzed acylation reaction, where the radical R means C1-C10-alkyl.

Abstract: 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 comprises 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.

Abstract: The present invention relates to a continuous process for preparing neral (cis-citral) in pure or enriched form by distillatively separating neral from substance mixtures comprising essentially neral and geranial (trans-citral). This distillative separation is performed in a dividing wall column or in a connection of two distillation columns in the form of a thermal coupling.

Abstract: The present invention relates to imidazolo-containing phosphinoborane compounds, to optically active ligands prepared using them, to transition metal complexes which comprise such ligands, and to catalysts which comprise such transition metal complexes. The present invention further relates to the particular processes for preparing the phosphinoborane compounds, the optically active ligands, the transition metal complexes and the catalysts, and to the use of the catalysts for organic transformation reactions. The present invention further relates to a process for preparing optically active ligands comprising imidazolo-containing phosphorus compounds using imidazolo-containing phosphinoborane compounds.

Abstract: The present invention relates to a process for preparing optically active carbonyl compounds by asymmetrically hydrogenating ?,?-unsaturated carbonyl compounds in the presence of optically active transition metal catalysts which are soluble in the reaction mixture and have at least one carbon monoxide ligand, the optically active catalyst which has at least one carbon monoxide ligand and is to be used in each case being prepared by pretreating a catalyst precursor with a gas mixture comprising carbon monoxide and hydrogen and the asymmetric hydrogenation being performed in the presence of carbon monoxide supplied additionally to the reaction mixture.

Abstract: A process for preparing optically active 2-methylalkan-1-ol of the general formula (III) comprising the following steps: carbonyl-selective reduction of 2-methylalk-2-en-1-al of the general formula (I) to 2-methylalk-2-en-1-ol of the general formula (II), (ii) enantioselective hydrogenation of 2-methylalk-2-en-1-ol to the general formula (iii), (iii) increasing the optical yield of the optically active 2-methylalkan-1-ol (III) obtained in step (ii) by a lipase-catalyzed acylation reaction, where the radical R means C1-C10-alkyl.

Abstract: The present invention relates to a process for preparing enriched isopulegol by crystallization from a melt comprising isopulegol. The invention relates specifically to a process for preparing enantiomerically enriched n-isopulegol proceeding from optically active isopulegol having a relatively low enantiomeric excess by crystallization from the melt. The invention further relates to a process for preparing menthol proceeding from enantiomerically and/or diastereomerically enriched n-isopulegol prepared by crystallization from the melt.

Abstract: The present invention relates to phosphorus compounds containing imidazole groups, to optically active ligands prepared using them, to transition metal complexes which comprise such ligands, and to catalysts which comprise such transition metal complexes. The present invention further relates to the particular processes for preparing the phosphorus compounds, the optically active ligands, the transition metal complexes and the catalysts, and also to the use of the catalysts for organic transformation reactions.

Abstract: A process for preparing optically active 2-methylalkan-1-ol of the general formula (III) comprising the following steps: (i) carbonyl-selective reduction of 2-methylalk-2-en-1-al of the general formula (I) to 2-methylalk-2-en-1-ol of the general formula (II), (ii) enantioselective hydrogenation of 2-methylalk-2-en-1-ol to the general formula (iii), (iii) increasing the optical yield of the optically active 2-methylalkan-1-ol (III) obtained in step (ii) by a lipase-catalyzed acylation reaction, where the radical R means C1-C10-alkyl.

Abstract: 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 comprises 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.

Abstract: The present invention relates to a continuous process for preparing neral (cis-citral) in pure or enriched form by distillatively separating neral from substance mixtures comprising essentially neral and geranial (trans-citral). This distillative separation is performed in a dividing wall column or in a connection of two distillation columns in the form of a thermal coupling.

Abstract: The present invention relates to a process for preparing optically active carbonyl compounds by asymmetrically hydrogenating ?,?-unsaturated carbonyl compounds in the presence of optically active transition metal catalysts which are soluble in the reaction mixture and have at least one carbon monoxide ligand, the optically active catalyst which has at least one carbon monoxide ligand and is to be used in each case being prepared by pretreating a catalyst precursor with a gas mixture comprising carbon monoxide and hydrogen and the asymmetric hydrogenation being performed in the presence of carbon monoxide supplied additionally to the reaction mixture.

Abstract: The present invention relates to a process for asymmetric synthesis in the presence of a chiral catalyst comprising at least one complex of a metal of transition group VIII with ligands capable of dimerization via noncovalent bonds, such catalysts and their use.

Abstract: The invention relates to a method for producing optically active 3-aminocarboxylic acid ester compounds. According to said method, an enantiomer mixture of a mono-N-acylated 3-aminocarboxylic acid ester, which mixture was previously enriched in an enantiomer, is subjected to deacylation and then to a further enantiomer enrichment by crystallization by adding an acidic salt-forming substance.

Abstract: The invention relates to a process for preparing optically active alkylsuccinic acid monoalkyl esters of the formula (I) where D and E are independently of one another H, C1-C10 alkyl, R is C1-C10 alkyl, aryl or alkylaryl.

Abstract: The present invention relates to a process for preparing optically active carbonyl compounds by asymmetrically hydrogenating ?,?-unsaturated carbonyl compounds in the presence of optically active transition metal catalysts which are soluble in the reaction mixture and have at least one carbon monoxide ligand. The present invention especially relates to a process for preparing optically active aldehydes or ketones, in particular citronellal, by asymmetrically hydrogenating the corresponding optically active ?,?-unsaturated aldehydes or ketones.

Abstract: The present invention relates to a process for asymmetric synthesis in the presence of a chiral catalyst comprising at least one complex of a metal of transition group VIII with ligands capable of dimerization via noncovalent bonds, such catalysts and their use.

Abstract: The present invention relates to a process for preparing optically active bisphosphinylalkanes from the correspondingly substituted, racemic 1,2-diols. The optically active bisphosphinylalkanes which can be obtained in this way are suitable as ligands for preparing chiral transition metal catalysts.