Construction of a quaternary carbon at the carbonyl carbon of the cyclohexane ring

High SN2′ selectivity in the allylic substitution of cyclohexylidene ethyl picolinates with copper reagents prepared from RMgBr and CuBr·Me2S was realized by addition of ZnX2 (X = I, Br, Cl). Furthermore, ZnX2 accelerated the reaction with the bulky iPr reagent.