title: trans-RuH(eta1-BH4)(binap)(1,2-diamine): a catalyst for asymmetric hydrogenation of simple ketones under base-free conditions.
abstract: 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 complex has been characterized by single crystal X-ray analysis as well as NMR and IR spectra. The new Ru complexes allow for asymmetric hydrogenation of simple ketones in 2-propanol without an additional strong base. Various base-sensitive ketones are convertible to chiral alcohols in a high enantiomeric purity with a substrate/catalyst ratio of up to 100 000 under mild conditions. Configurationally unstable 2-isopropyl- and 2-methoxycyclohexanone can be kinetically resolved with a high enantiomer discrimination. This procedure overcomes the drawback of an earlier method using RuCl2(diphosphine)(diamine) and an alkaline base, which sometimes causes undesired reactions such as ester exchange, epoxy-ring opening, beta-elimination, and polymerization of ketonic substrates.
authors.affiliation: Nagoya University, Department of Chemistry and Research Center for Materials Science, Chikusa, Nagoya 464-8602, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ohkuma
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Koizumi
authors.forename: Kilian
authors.initials: K
authors.lastname: Muñiz
authors.forename: Gerhard
authors.initials: G
authors.lastname: Hilt
authors.forename: Chizuko
authors.initials: C
authors.lastname: Kabuto
authors.forename: Ryoji
authors.initials: R
authors.lastname: Noyori