Design and Enantioselective Synthesis of Cashmeran Odorants by Using 'Enol Catalysis'

摘要

Novel Cashmeran odorants were designed by molecular modeling. Their short syntheses involve a novel asymmetric BrOnsted acid catalyzed Michael addition of unactivated -substituted ketones. This key transformation was realized by utilizing a new type of enol activation catalysis and affords different cyclic ketones bearing -quaternary stereocenters in good to excellent yields and with high enantioselectivity. Subsequent McMurry coupling and Saegusa-Ito oxidation furnished the enantiopure target odorants, one enantiomer of which indeed possesses the typical olfactory aspects of Cashmeran.