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Ru-Hydrogenation of Bulky Ketones with a Tridentate Ligand
M. B. Díaz-Valenzuela, S. D. Phillips, M. B. France, M. E. Gunn, M. L. Clarke*
University of St Andrews, UK and Washington and Lee University, Lexington, USA
23 March 2009 (online)
Current asymmetric hydrogena-tion catalysts for ketones typically involve [RuCl2(diphos)(diamine)] systems, related to earlier catalysts developed by Noyori. While highly effective for most substrate classes, severe limitations are encountered with sterically encumbered ketones. To overcome this problem, the authors have synthesized complex 1, possessing a tridentate P^N^NH2-type ligand which is thought to provide a more open coordination environment. With this system, various bulky ketone substrates are reduced in excellent yields and moderate to high enantioselectivities under hydrogenation or transfer hydrogenation parameters.