Allylic Substitution on Cyclopentene and -hexene Rings with Alkynylcopper Reagents

Abstract

Substitution of cyclic allylic picolinates with a reagent derived from TMS-CCMgBr and a copper salt was investigated. Although the previous type of reagent (TMSCCMgBr and CuBr·Me₂S) developed for linear allylic picolinates was less product selective and regioselective, the Cu(acac)₂-derived reagent was highly selective (94–95%) to afford the S_N2′ product in good yields. As an application, several C–C bond formations at the acetylenic carbon and the synthesis of the PG intermediate were studied with success