Higher-order cyano cuprate

Thienyl(cyano)copper lithium S Cu(CN)Li xhe reagent is obtained by reaction of thiophene with BuLi in THF at - 78° and then with CuCN at - 40°. The reagent is fairly stable and can be stored in THF at - 20° for about 2 months. It is inert, but is readily converted by addition of RLi or RMgX into a higher-order mixed cuprate, which is as efficient as the freshly prepared cuprate."1... 

Double substitution of geminal dibromides is best accomplished by treatment with an organocuprate, followed by the addition of an alkyl iodide to the crude reaction mixture. " The reaction has found especial application for the synthesis of dimethylcyclopropanes, ubiquitous in natural product chemistry. Excellent yields are often obtained with Me2CuLi, but with less reactive substrates higher order cyano-and thiocyano-cuprates sometimes provide better results. Spiro dialkylation of geminal dibromides has also been accomplished. Vicinal dibromides, on the other hand, afford alkenes upon treatment with dialkyl cuprates. ... 

A mechanism involving formation of the Af-lithinm derivative of 5h by proton abstraction with higher-order cyanocnprate, followed by C—N coupling of cyano cuprate, was suggested (Scheme 49) ". ... 

The solution structures of cyano-Gilman cuprates and lower-order cyanocuprates have been studied by cryoscopic measurements in THF [141]. The results of this study have in several cases shown ways to obtain useful single crystals of several higher- and lower-order cyanocuprates and consequently to determine their structures in the solid state. It appears that a number of these cyanocuprates retain their observed solid-state structure when dissolved in THF. 

---