title: Asymmetric hydrogenation of tert-alkyl ketones.
abstract: A combined system of RuCl2(tolbinap)(pica) and an alkaline or organic phosphazene base catalyzes asymmetric hydrogenation of sterically congested tert-alkyl ketones (TolBINAP = 2,2'-bis(di-4-tolylphosphino)-1,1'-binaphthyl, PICA = alpha-picolylamine). Hydrogenation with RuH(eta1-BH4)(tolbinap)(pica) does not require any strong base. Alcoholic solvents strongly affect the catalytic efficiency. The reaction proceeds smoothly in ethanol under 1-20 atm of H2 and at room temperature with a substrate to catalyst molar ratio of up to 100 000. Various aliphatic, aromatic, heteroaromatic, and olefinic tert-alkyl ketones are convertible to the corresponding chiral carbinols in high enantiomeric purity. Olefinic and heteroaromatic functions are left intact. Certain cyclic ketones are also usable. The mode of enantioface selection is consistent and predictable.
authors.affiliation: Department of Chemistry and Research Center for Materials Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ohkuma
authors.forename: Christian A
authors.initials: CA
authors.lastname: Sandoval
authors.forename: Rajagopal
authors.initials: R
authors.lastname: Srinivasan
authors.forename: Quinghong
authors.initials: Q
authors.lastname: Lin
authors.forename: Yinmao
authors.initials: Y
authors.lastname: Wei
authors.forename: Kilian
authors.initials: K
authors.lastname: Muñiz
authors.forename: Ryoji
authors.initials: R
authors.lastname: Noyori