Asymmetric 1,4‐conjugation addition of diethylzinc to cyclic enones catalyzed by a self‐assembled copper complex

A new self‐assembled catalyst system based on copper complex was developed for the 1,4‐conjugation addition of diethyl zinc to cyclic enones. The self‐assembled catalyst was readily prepared from ( R )‐[1,1′]binaphthalenyl‐2,2′‐diamine (1a), ( L )‐tryptophan (3f) and copper(I) chloride (CuCl). Several enones were found to be suitable substrates in the presence of the self‐assembled copper catalyst [10 mol% ( R )‐1a, 10 mol% ( L )‐3f and 10 mol% CuCl] under optimized conditions. The desired products were afforded with high isolated yields (up to 98%) and moderate to good enantioselectivities (up to 80% ee) in mild conditions (at 0 °C). Copyright © 2009 John Wiley & Sons, Ltd.