2,3]-Wittig Rearrangement of Crotyl Picolyl Ethers. Evaluation of the Electronic Effect as a Stereo-Directing Factor

Abstract

Abstract The title rearrangement is shown to exhibit syn diastereoselectivity independent of the crotyl geometry, the degree decreasing in the order: 2- > 4- >3-picolyl ether for the E series and in the opposite order for the Z series. These trends suggest that the electronic effect plays a profound but not sole factor in governing the orientational preference of the pyridyl group in the transition states.