Kinetic resolution of cis-3-alkylcyclohexene oxide by a chiral lithium amide - An application to a synthesis of both enantiomers of isomenthone

Kinetic resolution of cis-3-alkylcyclohexene oxide (1) was examined using c hiral lithium amide, lithium (S)-2-(pyrrolidin-1-yl)methylpyrrolidide (2). High cc (84-->98% eel of 1 was obtained by using 1.1-1.2 equiv of 2, while 6-alkyl-2-cyclohexenol (3) was obtained in moderate ee (60-68% eel by using 0.5-0.75 equiv of 2. Both enantiomers of cis-2-isopropyl-5-methylcyclohexa none (isomenthone)were derived from (1S,2R,3R)-(+)-3-isopropylcyclohexene o xide (1b) or (1R,6R)-(-)-6-isopropyl-2-cyclohexenol (3b) in a few steps, re spectively.