Asymmetric hydrogenation of tert-alkyl ketones

Takeshi Ohkuma; Christian A Sandoval; Rajagopal Srinivasan; Quinghong Lin; Yinmao Wei; Kilian Muñiz; Ryoji Noyori

doi:10.1021/ja052071+

Asymmetric hydrogenation of tert-alkyl ketones

J Am Chem Soc. 2005 Jun 15;127(23):8288-9. doi: 10.1021/ja052071+.

Authors

Takeshi Ohkuma¹, Christian A Sandoval, Rajagopal Srinivasan, Quinghong Lin, Yinmao Wei, Kilian Muñiz, Ryoji Noyori

Affiliation

¹ Department of Chemistry and Research Center for Materials Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.

PMID: 15941254
DOI: 10.1021/ja052071+

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.