Stereoselective Synthesis of Medium-Sized Cyclic Compounds by Means of Tandem Reactions of a Cyclic Oxosulfonium Ylide with Acetates of Baylis-Hillman Adducts

摘要

Treatment of a five-membered cyclic oxosulfonium ylide 3 with #beta#-acetoxy-#alpha#-methylene ketonesin the presence of two equimolar amounts of base afforded the cycloheptene oxide derivatives 7a-i as single stereoisomers in 19-77% yields.The products were considered to form through a Michael-type addition of the ylide,followed by elimination of the acetoxy group and an intramolecular Corey-Chaykovsky reaction.On the other hand,the same treatment,when using a six-membered oxosulfonium ylide,gave the coresponding cycloocteen oxide derivatives in moderate yields,with the products formed in a ca. 4:1 mixture of stereoisomers, a fact correlated with differences in the configuration of the sulfur atom in the sulfinyl group.