The reactions of cyclohexenone, cyclopentenone, (£)-3-penten-2-one, and (£)-3-octen-2-one with chiral organo-(hetero)cuprates containing Me, n-Bu, or rert-butyl transferable ligands afforded the adducts in optical yields as high as 41-83%. Variation in the chiral nontransferable ligands derived from (S)-proline involves, formally, replacement of the hydroxy group of (S)-prolinol with a methoxy, pyrrolidyl, phenylthio, or methylthio substituent. The extent of asymmetric induction was a function of all the experimental variables while the absolute stereochemistry was dependent upon substrate structure, cuprate composition, and solvent.We have, over the past few years, examined the chemoand stereoselective reactions of organocuprates with a-oxoketene dithioacetals1 and vinylogous thiol esters.2 These studies provided considerable insight into the complexities of organocopper conjugate addition reactions since the observed selectivities were influenced by all of the experimental variables. Our experience in unravelling and exploiting the complex influence of substrate structure, cuprate reagent, cuprate composition, transferable ligand, temperature, and solvent in these substitution reactions (conjugate addition-elimination) coupled with recent advances in the development of second generation organocopper reagents (e.g., amido,3 phosphide,3 and "higher order"4 cuprates) encouraged us to search for procedures for effecting the conjugate addition process with asymmetric induction. We now report on the reactions of four enones with chiral organo(hetero)cuprates and the influence of various experimental parameters upon the extent and absolute stereochemistry of the asymmetric induction. The role of substrate structure, cuprate reagent, chiral ligand, cuprate composition, transferable ligand, solvent, temperature, and added salts have been examined. A simple model has been proposed to account for the results which display good internal consistency over a wide range of experimental variation.Background. Organocopper conjugate addition reactions occupy a central niche in synthetic organic chemistry.5 6They provide one of the few generally reliable methods for constructing new carbon-carbon bonds ß to a carbonyl functional group and the type and variety of ligands that can be transferred to an ,ßunsaturated carbonyl compound complement the stabilized carbanions employed in the Michael reaction. The importance of this reaction has prompted numerous searches for procedures and methods to effect the conjugate addition process with asymmetric induction. These efforts have focused on four strategies utilizing either: (1) a chiral medium generally in the form of chiral coordinating ligands, (2) cuprates containing a chiral nontransferable ligand (RL*CuM), (3) cuprates containing a chiral transferable ligand (R*LCuM), or (4) chiral substrates. The methods involving chiral substrates or cuprates containing chiral transferable ligands generate, initially at least, diastereomeric products, and procedures have been developed that af...
