From the stoichiometry, it is apparent that one equivalent of the R group is wasted as an ill-characterized alkylcopper species (likely polymeric;
usually converted to RH upon aqueous workup) in the most common form of the Corey–House synthesis. To avoid this for cases where R is a precious or
complex fragment, a reagent (R)(RU)CuM, where RU is an untransferable dummy ligand (e.g., RU = cyano, alkynyl, 2-thienyl, etc.) can be prepared and
used instead. |