Application of deoxycholic acid-based copper-phosphite complexes as ligands in the enantioselective conjugate addition of diethylzinc to acyclic enones

Four phosphites obtained by linking enantiomerically pure binaphthylchlorophosphite to the two different hydroxy groups of deoxycholic acid were synthesized and used as chiral ligands in the enantioselective copper-catalyzed 1,4-addition of diethylzinc to acyclic enones. The ligands were screened for activity and enantioselectivity using chalcone as the substrate to establish the influence of the absolute configuration of the binaphthyl moiety as well as the position on the cholestanic backbone of the phosphite moiety. The ligand affording the best results was eventually used in the copper-catalyzed 1,4-addition to various acyclic enones, affording the alkylation products in good yields and e.e.s up to 78%. (C) 2003 Elsevier Science Ltd. All rights reserved.