trans-RuH(η-BH4)(binap)(1,2-diamine): A Catalyst for Asymmetric Hydrogenation of Simple Ketones under Base-Free Conditions

• DOI: 10.1021/ja026136+
• Publication Date: 2002-07-26T06:11:09Z
• Authors: Takeshi Ohkuma; Masatoshi Koizumi; Kilian Muñiz; Gerhard Hilt; Chizuko Kabuto; Ryoji Noyori
• Keywords: Enantiomeric excess; Base (topology); Asymmetric hydrogenation; Isopropyl

Reaction of a chiral RuCl2(diphosphine)(1,2-diamine) complex and NaBH4 forms trans-RuH(eta1-BH4)(diphosphine)(1,2-diamine) quantitatively. The TolBINAP/DPEN Ru has been characterized by single crystal X-ray analysis as well NMR IR spectra. new complexes allow for asymmetric hydrogenation simple ketones in 2-propanol without an additional strong base. Various base-sensitive are convertible to alcohols high enantiomeric purity with substrate/catalyst ratio up 100 000 under mild conditions. Configurationally unstable 2-isopropyl- 2-methoxycyclohexanone can be kinetically resolved enantiomer discrimination. This procedure overcomes the drawback earlier method using RuCl2(diphosphine)(diamine) alkaline base, which sometimes causes undesired reactions such ester exchange, epoxy-ring opening, beta-elimination, polymerization ketonic substrates.