A series of chiral, C2 symmetric tridentate N-heterocyclic carbene precursors, containing two N-functionalized hydroxyl or alkoxyl groups, were synthesized. They were applied to catalyze the asymmetric conjugate addition of diethylzinc to cyclohex-2-enone and cyclopent-2-enone. Enantioselectivity of corresponding reactions can be accomplished with up to 76% ee, and 65% ee, respectively. Flip of major enantiorner was observed when different bases or copper sources were utilized.
Intramolecular conjugate reduction-aldol addition reactions of β＇-oxoalkyl a,fl-unsaturated carboxylates were performed in the presence of copper catalysts generated in situ from copper salts, phosphine ligands and silanes. Moderate to good yields and high diastereoselectivities were obtained in 15 min to 3 h using bis[（2-diphenyl- phosphino）phenyl] ether as the ligand.
Copper hydride-catalyzed conjugate reduction-intermolecular aldol addition domino reactions were realized using α,β-unsaturated carboxylates as hydride acceptors and a silane as the reducing reagent. High diastereoselec- tivities were achieved with 4,5-bis（diphenylphosphino）-9,9-dimethylxanthene as the ligand and tert-butyl acrylate as the hydride acceptor.
