Reactions of stoichiometric higher order, mixed lithio magnesio organocuprates

Novel higher order cuprates, R(2-thienyl)Cu(CN)LiMgBr (2), are prepared from the 1:1:1 combination of CuCN, 2-lithiothiophene and RMgX. Reactions of various members of this new class of reagents are described, including substitution and conjugate addition processes, where the ligand derived from the Grignard reagent is selectively transferred. The effects of added BF 3 .Et 2 O are discussed. Some comparison reactions with the corresponding lower order reagents, RCu(CN)MgBr, have also been carried out. Evidence is presented suggesting that species 2, unlike their dilithio analogs, are not discrete.