Highly enantioselective copper-catalyzed 1,4-conjugate addition of diethylzinc to cyclic enones and α,β-unsaturated lactones

A significant improvement in enantioselectivity has been achieved in the 1,4-additions of diethylzinc to 2-cyclopentenone, 2-cyclohexenone and 5,6-hydro-2H-pyran-2-one (up to 93%, 98% and 94% ee, respectively) by using a chiral diphosphite-copper catalyst under suitable reaction conditions. (C) 2004 Elsevier Ltd. All rights reserved.