On the role of additives in alkyl–alkyl Negishi cross-couplings

Abstract

An additives study for the alkyl-alkyl Negishi reaction using an NHC-Pd catalyst revealed that bromide salts promote coupling while the cation is mechanistically benign. A double titration revealed that the cross-coupling begins at a 1 : 1 ratio of LiBr : (n)BuZnBr, suggesting that a higher-order zincate, presumably Li(m)Zn((n)Bu)Br(3)((2-m)-), is the active transmetalating agent.