Allylic substitution on cyclopentene and -hexene rings with alkynylcopper reagents

Article abstract of DOI:10.1021/ol202711k

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.