Development of New Chiral Transition-Metal Catalysts for Highly Efficient Asymmetric Synthesis

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We had already developed atroisomeric bis (triarylphosphine) ligand, 2, 2^'-bis (diphenylphosphino)-1, 1^'-binaphthyl (abbreviated to BINAP) and showed that its metal complexes had high efficiency as catalysts for asymmetric hydrogenation of -acylaminoacrylic acids and asymmetric isomerization of allylamines into enamines by 1, 3-hydrogen migration. We also reported synthesis of Ru (OCOR) _2 (binap), the first mononuclear BINAP-Ru (II) complexes, and demonstrated that they are highly efficient catalysts for the asymmetric hydrogenations of emanides, alpha, beta- and beta, gamma-unsaturated carboxylic acids, allylic and homoallylic alcohols. In order to expand the synthetic utility of BINAP ligand, we have continued our investigation on the development of new highly efficient asymmetric reactions catalyzed by various BINAP-Ru (II) complexes which have been summarized below.(1) New cationic BINAP-Ru (II) complexes [RuX (binap) (arene)]y (X=Cl, Br, and I ; Y = Cl, Br, I, BF_<4'> and BPh_4 … More ; arene = benzene and p-cymene) have been synthesized in high yields and the molecular structures have been determined by spectroscopic and X-ray analyses. We have shown that these complexes are highly efficient catalysts for enantioselective hydrogenation of various unsaturated substrates. Especially important is the high efficiency of these complexes as catalysts for asymmetric hydrogenation of functionalized ketones.(2) A number of substituted BINAP derivatives have been synthesized. Various factors controlling the catalytic activity and selectivity of the asymmetric hydrogenation of ketones have been elucidated by use of these complexes.(3) Highly diastereoselective hydrogenation of methyl 2-benzamidomethyl-3-oxobutanoate via dynamic kinetic resolution has been accomplished by using [RuI ((R-3, 5-di-tert-Bu-binap) (p-cymene)] I as catalyst, giving methyl (2S, 3R-2-benzamidomethyl-3-hydroxybutanoate (98% 99%), a versatile intermediate intermediate for the synthesis of beta-lactam antibiotics.(4) Mechanism of asymmetric hydrogenation of alpha,beta-unsaturated carboxylic acids catalyzed by Ru (OCOCH_3) _2 (bianp) has been elucidated based mainly on deuterium-labeled experiments.(5) New monocationic trinuclear complexes [Ru_3X_5 (binap) _3] Y have been prepared and their roles in catalytic reactions have been discussed.(6) Several new bis (triaryphophine) ligands have been synthesized and their use for asymmetric catalysis have been investigated. Less