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) catalytic hydrogenation of neral and/or geranial to give citronellal, b) cyclization of citronellal to isopulegol in the presence of an acidic catalyst, c) purification of isopulegol by crystallization and d) catalytic hydrogenation of isopulegol to give menthol.

Abstract: The present invention relates to a process for preparing 4,4?-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols), in particular for preparing 4,4?-[1-(trifluoromethyl)ethylidene]bis(2,6-diphenylphenol), which comprises the self-condensation of cyclohexanone in the presence of a basic catalyst to form tricyclic condensation products, dehydrogenation of the resulting tricyclic condensation products in the presence of a supported transition metal catalyst in the condensed phase to form 2,6-diphenylphenol and reaction of the 2,6-diphenylphenol with a trifluoromethyl ketone. The invention further provides an improved process for preparing 2,6-diphenylphenol by aldol self-condensation of cyclohexanone.

Abstract: The present invention relates to an improved process for preparing a substituted or unsubstituted phenylcyclohexane by catalytic hydrogenation of a substituted or unsubstituted biphenyl.

Abstract: The present invention relates to a method of working up an aluminium-containing reaction product from the production of isopulegol by cyclization of citronellal in the presence of complex compounds, comprising at least one ligand of the formula (I), where Ar1, Ar2, Ar3, Ar4 are chosen from C6-C15-aryl or C2-C15-hetero; R1, R2, R3, R4 are chosen from H, C1-C6-alkyl, C1-C6-perfluoroalkyl, C1-C6-alkoxy, C7-C12-aralkyl, halogen, SiR5bR6bR7b, C6-C10-aryl, NR8bR9b, SR10b, NO2; and where R1 or R2 and/or R3 or R4, together with A, can form an aromatic or nonaromatic cycle; etc.; in which a) the aluminum-containing reaction product is subjected to distillative separation, b) the isopulegol-depleted bottom product is brought into close contact with an aqueous base and c) the ligand of the formula (I) is separated off from the organic phase, preferably by crystallization. Moreover, the invention relates to a method of producing isopulegol, and to a method of producing menthol.

Abstract: The present invention relates to a process for the preparation of 2-substituted 4-hydroxy-4-methyltetrahydropyranols by reacting 3-methylbut-3-en-1-ol (isoprenol) with the corresponding aldehydes in the presence of a strongly acidic cation exchanger. Specifically, the present invention relates to a corresponding process for the preparation of 2-isobutyl-4-hydroxy-4-methyltetrahydropyran by reacting isoprenol with isovaleraldehyde.

Abstract: Process for the preparation of 2-substituted 4-hydroxy-4-methyltetrahydropyrans of the formula (I) where the radical R1 is a straight-chain or branched alkyl or alkenyl radical having 1 to 12 carbon atoms, an optionally alkyl-substituted cycloalkyl radical having in total 3 to 12 carbon atoms or an optionally alkyl- and/or alkoxy-substituted aryl radical having in total 6 to 12 carbon atoms, comprising the reaction of 3-methylbut-3-en-1-ol of the formula (II) with an aldehyde of the formula (III) R1—CHO??(III), where the radical R1 has the same meaning as in formula (I) and where the reaction is carried out in the presence of water and in the presence of a strongly acidic cation exchanger, and then the isolation and/or the distillative separation is carried out in a dividing wall column or in an interconnection of (at least) two distillation columns in the form of a thermal coupling and one or more side take-off points at an absolute operating pressure of up to 500 mbar.

Abstract: The present invention relates to a process for the preparation of 2-substituted 4-hydroxy-4-methyltetrahydropyrans by reacting 3-methylbut-3-en-1-ol(isoprenol) with the corresponding alkenealdehydes in the presence of a strongly acidic ion exchanger with subsequent hydrogenation. Specifically, the present invention relates to a corresponding process for the preparation of 2-isobutyl-4-hydroxy-4-methyltetrahydropyran by reacting isoprenol with prenal, with subsequent hydrogenation.

Abstract: The present invention relates to a method of working up an aluminum-containing reaction product from the production of isopulegol by cyclization of citronellal in the presence of complex compounds, comprising at least one ligand of the formula (I), where R1, R2, R3 are chosen from hydrogen, halogen, nitro, C1-C8-alkyl, C1-C8-alkoxy, di(C1-C4-alkyl)amino and aryl; R4, R5 are chosen from halogen, nitro, C1-C8-alkyl, C1-C8-alkoxy, di(C1-C4-alkyl)amino, aryl or heteroaryl; in which a) the reaction product is subjected to distillative separation to obtain an isopulegol-enriched top product and an isopulegol-depleted bottom product and b) the ligand of the formula (I) is separated off from the bottom product. Moreover, the invention relates to a method of producing isopulegol, and to a method of producing menthol.

Abstract: The present invention relates to a process for preparing racemic or optically active menthol by catalytically hydrogenating racemic or optically active isopulegol in the presence of hydrogen and catalysts which comprise nickel-, copper-, zirconium- and molybdenum-containing compounds. The present invention relates specifically to a corresponding process far continuously catalytically hydrogenating L-isopulegol to L-menthol.

Abstract: The present invention relates to a process for preparing 4,4?-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols), in particular for preparing 4,4?-[1-(trifluoromethyl)ethylidene]bis(2,6-diphenylphenol), which comprises the self-condensation of cyclohexanone in the presence of a basic catalyst to form tricyclic condensation products, dehydrogenation of the resulting tricyclic condensation products in the presence of a supported transition metal catalyst in the condensed phase to form 2,6-diphenylphenol and reaction of the 2,6-diphenylphenol with a trifluoromethyl ketone. The invention further provides an improved process for preparing 2,6-diphenylphenol by aldol self-condensation of cyclohexanone.

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 racemic or optically active menthol in pure or enriched form by distillatively separating menthol from substance mixtures which comprise essentially menthol and diastereomers thereof. This distillatiive separation is performed in a dividing wall column with 50 to 300 theoretical plates and one or more side draw points at an absolute operating pressure of 5 to 500 mbar.

Abstract: The present invention relates to a process for preparing racemic or optically active menthol by catalytically hydrogenating racemic or optically active isopulegol in the presence of hydrogen and catalysts which comprise nickel-, copper-, zirconium- and molybdenum-containing compounds. The present invention relates specifically to a corresponding process far continuously catalytically hydrogenating L-isopulegol to L-menthol.

Abstract: The present invention relates to a method of working up an aluminum-containing reaction product from the production of isopulegol by cyclization of citronellal in the presence of complex compounds, comprising at least one ligand of the formula (I), where R1, R2, R3 are chosen from hydrogen, halogen, nitro, C1-C8-alkyl, C1-C8-alkoxy, di(C1-C4-alkyl)amino and aryl; R4, R5 are chosen from halogen, nitro, C1-C8-alkyl, C1-C8-alkoxy, di(C1-C4-alkyl)amino, aryl or heteroaryl; in which a) the reaction product is subjected to distillative separation to obtain an isopulegol-enriched top product and an isopulegol-depleted bottom product and b) the ligand of the formula (I) is separated off from the bottom product. Moreover, the invention relates to a method of producing isopulegol, and to a method of producing menthol.

Abstract: The present invention relates to a method of working up an aluminium-containing reaction product from the production of isopulegol by cyclization of citronellal in the presence of complex compounds, comprising at least one ligand of the formula (I), where Ar1, Ar2, Ar3, Ar4 are chosen from C6-C15-aryl or C2-C15-hetero; R1, R2, R3, R4 are chosen from H, C1-C6-alkyl, C1-C6-perfluoroalkyl, C1-C6-alkoxy, C7-C12-aralkyl, halogen, SiR5bR6bR7b, C6-C10-aryl, NR8bR9b, SR10b, NO2; and where R1 or R2 and/or R3 or R4, together with A, can form an aromatic or nonaromatic cycle; etc.; in which a) the aluminum-containing reaction product is subjected to distillative separation, b) the isopulegol-depleted bottom product is brought into close contact with an aqueous base and c) the ligand of the formula (I) is separated off from the organic phase, preferably by crystallization. Moreover, the invention relates to a method of producing isopulegol, and to a method of producing menthol.