Production of isopulegol, for use especially in the production of optically active menthol for aroma applications, involves cyclisation of citronellal in presence of a tris-1,3-diaryl-2-naphthoxy-aluminum catalyst

摘要

A method for the production of isopulegol involves the cyclisation of citronellal in presence of a tris-(1,3-diaryl-2-naphthoxy)-aluminum compound as catalyst. A method for the production of isopulegol (formula I) involves the cyclisation of citronellal (formula II) in presence of a tris-(1,3-diaryl-2-naphthoxy)-aluminum catalyst of formula (III), in which R1>, R2>H, halogen and/or 1-4C alkyl (in the o-, m- and/or p- positions); R3>-R6>H, halogen or 1-4C alkyl. Independent claims are included for (1) aluminium compounds of formula (III) (2) a method for the production of 1,3-diaryl-2-naphthols of formula (VI) by reacting a benzaldehyde of formula (XI) with a diphenyl ketone of formula (XII) to give an unsaturated ketone of formula (XIII), then reacting (XIII) with bromine and cyclising the product by treatment with a carbonate. [Image] [Image] [Image].