Enantioselectivity switch in copper-catalyzed conjugate addition reactions under the influence of a chiral N-heterocyclic carbene–silver complex

摘要

The asymmetric 1,4-addition of Et _(2) Zn to 2-cyclohexen-1-one using a Cu( I ) salt/N-heterocyclic carbene (NHC)–Ag complex catalytic system afforded optically active 3-ethylcyclohexanone. The reversal of enantioselectivity using the same catalytic system was achieved by changing the order of the addition of substrates.