Synthesis of Enantiopure 2-Malonylvinyl Sulfoxides via Addition-Elimination Reactions of 2-Halo- and 2-(Mesyloxy)vinyl Sulfoxides
摘要:
Enantiomerically pure (E)-2-bromo- and (E)-2-iodovinyl sulfoxides 3a and 3b have been prepared in multigram quantities from (E)-1,2-bis(tri-n-butylstannyl)ethene; enantiomerically pure (E)-2-(mesyloxy) vinyl sulfoxide 3c has been synthesized by reaction of the enolate derived from condensation of 1-lithiomethyl p-tolyl sulfoxide and DMF with methanesulfonyl chloride. These compounds react with anions derived from diethyl alkylmalonates to produce enantiopure 2-malonylvinyl sulfoxides in good to excellent yields and with a high degree of stereoselectivity. The transformations proceed through an ''addition-rotation-elimination'' sequence, and the stereochemical results reinforce the concept that nucleophilic additions to vinyl sulfoxides are sterically controlled and occur predominately syn to the sulfinyl electron lone pair.