Enantioselective copper-catalyzed reductive Michael cyclizations.

In the presence of siloxanes as stoichiometric reductants, chiral copper-bisphosphine complexes catalyze highly enantioselective reductive Michael cyclizations of substrates containing two alpha,beta-unsaturated carbonyl moieties. The diastereochemical outcome of these reactions is dependent upon whether biaryl- or ferrocene-based chiral bisphosphines are employed.