Allylic substitution reactions with Grignard reagents catalyzed by imidazolium and 4,5-dihydroimidazolium carbene–CuCl complexes

Imidazolium and 4,5-dihydroimidazolium carbene–CuCl complexes effectively catalyzed the substitution reaction of allylic compounds with Grignard reagents in an SN2′-selective fashion. It was noteworthy that the amount of the imidazolium carbene-CuCl complex could be reduced to 0.001 mol% and the catalysis recorded a high TON (105). Based on the experimental results, the ate-type complex(es) such as [(imidazolium carbene)-CuR2]−(MgX)+ was postulated as an active species.