Synthesis via vinyl sulfones. 27. Total synthesis of cephalotaxine. The first example of an intramolecular [4 + 2] cycloaddition where the dienophile has been delivered from the face opposite to the tethering moiety
Synthesis via vinyl sulfones. 18. Rapid access to a series of highly functionalized .alpha.,.beta.-unsaturated cyclopentenones. A caveat on aminospirocyclization
Conjugate addition reactions of a (diethoxyphosphinoyl)difluoromethyl anion equivalent to acyclic and cyclic vinyl sulfones
作者:K. Blades、D. Lapôtre、J.M. Percy
DOI:10.1016/s0040-4039(97)01313-0
日期:1997.8
Cerium-mediated conjugateadditions of (diethoxyphosphinoyl)difluoromethyllithium to cyclic vinylsulfones proceeded smoothly; reduction afforded the products of formal alkylation, attaching the difluoromethylene phosphonate group to a secondary carbon atom. With acyclic vinylsulfones, the addition was considerably less efficient and deprotonation competed with addition. Addition failed completely