CATIONIC BINAP-RU(II) HALIDE-COMPLEXES - HIGHLY EFFICIENT CATALYSTS FOR STEREOSELECTIVE ASYMMETRIC HYDROGENATION OF ALPHA-FUNCTIONALIZED AND BETA-FUNCTIONALIZED KETONES

Cationic ruthenium-BINAP complexes 5, 7, and 10 of the formula [RuX((S )-BINAP) (arene)]Y, where X = Cl, Br, I; Y = Cl, Br, I, BF4, B(C6H5)(4 ); arene = benzene, p-cymene, ethyl benzoate, and their enantiomers ha ve been prepared by the reaction of arene-ruthenium halide complexes 4 , 6, and 9 with (S)-BINAP or (R)-BINAP. Structures of the complexes we re established by spectroscopy, conductivity, and a single-crystal X-r ay analysis (5d: orthorhombic, P2(1)2(1)2; a 20.141(2) Angstrom, b = 1 8.504(1) Angstrom, c 12.241(1) Angstrom V = 4562.0(7) Angstrom(3), Z = 4, R = 0.078 for unique 4177 reflections). BINAP derivatives with var ious substituents at the para and meta positions of four phenyl rings on phosphorus atoms and their cationic Ru(II) complexes have also been synthesized. These BINAP-Ru(II) complexes have been used as catalysts for the asymmetric hydrogenation of various unsaturated organic compo unds such as alpha- and beta-keto esters, allylic alcohols, and alpha, beta-unsaturated carboxylic acids in excellent diastereo- and/or enant ioselectivities. Catalytic activities and stereoselectivities depend h ighly on reaction conditions such as solvent, temperature, and additiv es. Variation of halogen ligands bound to ruthenium atom and substitue nts on four phenyl rings of BINAP also have exerted remarkable effects on the efficiency of the catalysis. Asymmetric hydrogenation of methy l (+/-)-2-(benzamidomethyl)-3-oxobutanoate catalyzed by the species de rived from 9c and 3,5((t)Bu)(2)-BINAP afforded the corresponding syn-( 2S,3R)-17 in 98% de and 99% ee.