Reaction of a Cyclic Phosphonium Ylide with α,β-Unsaturated Thioesters
摘要:
The tandem Michael-intramolecular Wittig reactions of a five-membered cyclic phosphonium ylide (2) with alpha,beta-unsaturated thioesters afforded cycloheptene derivatives 4a-g in 29-58% yield. The reaction proceeded via a rigid phosphabicyclic intermediate and supplied the cycloheptene derivatives with high stereoselectivity. On the other hand, although the reaction using S-cyclohexyl cyclopentenethioearboxylate 5a as a substrate gave a 1:1 mixture of cis and trans adducts of the corresponding hydroazulene derivatives, the reaction of S-tert-butyl cyclopentenethiocarboxylate 5b gave cis-adduct as a major product (cis:trans = 17:3).