The Use of 15N NMR Spectroscopy To Resolve the “Higher Order Cyanocuprate” Controversy: 15N, 6Li,and 13C NMR Spectroscopic Investigations of CuCN-Derived Butyl Cuprates

Structure 1 is the major component obtained by the reaction of two equivalents of RLi and one equivalent of CuCN; other proposed structures can now be ruled out on the basis of ¹⁵N NMR spectroscopic and theoretical studies. Thus, these useful synthetic reagents should be considered as cyano-Gilman reagents R₂CuLi⋅LiCN and not “higher order cyanocuprates” R₂Cu(CN)Li₂.