title: Cooperative catalysis of metal and O-H···O/sp3-C-H···O two-point hydrogen bonds in alcoholic solvents: Cu-catalyzed enantioselective direct alkynylation of aldehydes with terminal alkynes.
abstract: Catalyst-substrate hydrogen bonds in artificial catalysts usually occur in aprotic solvents, but not in protic solvents, in contrast to enzymatic catalysis. We report a case in which ligand-substrate hydrogen-bonding interactions cooperate with a transition-metal center in alcoholic solvents for enantioselective catalysis. Copper(I) complexes with prolinol-based hydroxy amino phosphane chiral ligands catalytically promoted the direct alkynylation of aldehydes with terminal alkynes in alcoholic solvents to afford nonracemic secondary propargylic alcohols with high enantioselectivities. Quantum-mechanical calculations of enantiodiscriminating transition states show the occurrence of a nonclassical sp(3)-C-H···O hydrogen bond as a secondary interaction between the ligand and substrate, which results in highly directional catalyst-substrate two-point hydrogen bonding.
authors: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan), Fax: (+81) 11-706-3749.
authors: Takaoki
authors: T
authors: Ishii
authors: Ryo
authors: R
authors: Watanabe
authors: Toshimitsu
authors: T
authors: Moriya
authors: Hirohisa
authors: H
authors: Ohmiya
authors: Seiji
authors: S
authors: Mori
authors: Masaya
authors: M
authors: Sawamura
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D006860:Hydrogen Bonding; D015394:Molecular Structure; D012997:Solvents; D013237:Stereoisomerism
chemical_list: D000447:Aldehydes; D000480:Alkynes; D012997:Solvents; D003300:Copper
keywords: asymmetric catalysis; cooperative catalysis; copper; density functional calculations; hydrogen bonds