Phosphine-Catalyzed Intramolecular Cyclizations of α-Nitroethylallenoates Forming (Z)-Furanone Oximes
A novel and efficient phosphine-catalyzed intramolecular cyclization of α-nitroethylallenic esters is reported. This process appears to be practical for the stereoselective syntheses of (Z)-furan-2(3H)-one oxime derivatives in excellent yields. Mechanisti
Enantioselective organocatalytic Michael-Wittig-Michael-Michael reaction: Dichotomous construction of pentasubstituted cyclopentanecarbaldehydes and pentasubstituted cyclohexanecarbaldehydes
Michael addition of carbethoxymethylenetriphenylphosphorane (a Wittig reagent) to nitroalkenes, followed by a reaction with ethyl formylformate and cinnamaldehydes, or formaldehyde and cinnamaldehydes, provided the respective pentasubstituted cyclopentanecarbaldehydes bearing a quaternary carbon center and pentasubstituted cyclohexanecarbaldehydes having five contiguous stereocenters with excellent enantioselectivities (up to >99% ee).