Conjugate Addition Reactions of α-Aminoalkylcuprates with α,β-Enones and Enals

Deprotonation of Boc-protected amines with sec-BuLi or transmetallation of α-aminostannanes with n-BuLi affords α-aminoalkyllithium reagents which can be converted into α-aminoalkylcuprate reagents with CuCN or THF soluble CuCN·2LiCl. These reagents undergo conjugate addition reactions with α,β-enones and enals. Reagents prepared from 2 equiv. of the α-aminoalkyllithium reagent give higher yields of conjugate adducts than those prepared from RCuCNLi, particularly when insoluble CuCN is employed. When CuCN·2LiCl is used, the two cuprate reagents give comparable yields of 1,4-adducts and the RCuCNLi reagent, economical in α-aminoalkyl ligand, is preferred. The Boc protecting group can be removed with PhOH/TMSCl and the amino ketone isolated as the hydrochloride salt.