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

Article abstract of DOI:10.3987/COM-99-S122

Kinetic resolution of cis-3-alkylcyclohexene oxide (1) was examined using chiral lithium amide, lithium (S)-2-(pyrrolidin-1-yl)methylpyrrolidide (2). High ee (84->98% ee) 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% ee) by using 0.5-0.75 equiv of 2. Both enantiomers of cis-2-isopropyl-5- methylcyclohexanone (isomenthone) were derived from (1S,2R,3R)-(+)-3- isopropylcyclohexene oxide (1b) or (1R, 6R)-(-)-6-isopropyl-2-cyclohexenol (3b) in a few steps, respectively.