Propyl-menthol

A general way to reduce a C=N bond to an optically active amine is still elusive. Attempted reduction, using a LAH/(-)-menthol reagent, of 2-substituted iminium salts (96, R = methyl, ethyl, propyl or benzyl) or (97, R = methyl, ethyl, propyl or benzyl) and imine (98) gives the corresponding amines with low optical purities. 

Fair 7i-propyl alcohol (40%), isobutyl alcohol, scc.-butyl alcohol, 2-methyl-1-butanol, isoamyl alcohol, ZerZ.-amyl alcohol, menthol Poor ethyl alcohol (30%), benzyl alcohol... 

Hexahydrothymol 2-isopropyl-5-methylcyclohexanol 4-iso-propyl-l-methylcyclohexan-3-ol 3-p-menthanol p-menthan-3-ol dZ-menthol peppermint camphor racemic menthol. 

Thymol, isopropyl meta-cresol, is a precursor of L-menthol. Meta-cresol with a purity of >98.5% must be used as the starting material for thymol production, because the isomer, 2-iso-propyl-4-methyl phenol derived from p-cresol is the main contaminant and cannot be easily separated from thymol. 

Asymmetric reductions with chiral complex metal hydrides and tricoordinate hydride reagents are rare. Iminium salts25 26 and imines27 have been reduced by chiral complex aluminum hydrides. Optically active 2-substituted Ar-methylpiperidine was obtained by reduction of the corresponding 3,4,5,6-tetrahydropyridinium perchlorate with (—)-menthol lithium aluminum hydride. The optical purity for the -propyl derivative was 12% in favor of the S configuration. Similar reductions of imines prepared from acetophenone and propiophenonc with (-)-mcn-thol-lithium aluminum hydride and ( + )-borneol-lithium aluminum hydride reagents resulted in low (<10%) optical yields in those examples where optical yields could be calculated. 

Liquid. Slight odor resembling menthol. Pure Decalin does not smell of naphthalene. Volatile with steam. The commercial product may be practically all tram-Decalin, or a mixture contg up to 60% cis-Decalin. The commercial mixture has a flash pt (closed cup) of about 136 F (58 0. Autoignition temp 504 F. lnsol in water very sol in alcohol, methanol, ether, chloroform. Miscible with propyl and isopropyl alcohol miscible with most ketones and esters. LDM orally in rats 4.2 g/kg. Lethal conen for rats in air 500 ppm, Smyth er al.. Arch. Ind. Hyg Occup. Med. 4, 119 (1951). 

Geraniol Linalool Menthone a-Terpineol y3-Terpineol Propyl succinate Citronellol Menthol 2-Hexylthioethyl vinyl ether... 

Linalool o -Terpineol /8-Terpineol Propyl succinate Citronellol Menthol Capric acid Ethyl caprylate Isoamyl isovalerate n-Decyl alcohol Isoamyl sulfide Isobutyl benzoate Terpineol methyl ether Ethyl pelargonate Isoamyl carbonate 1,3,5-Triethylbenzene Bornyl acetate Bornyl ethyl ether Tridecane... 

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