Benzimidazoles as Ligands in the Ruthenium-Catalyzed Enantioselective Bifunctional Hydrogenation of Ketones

摘要: A series of Cl2Ru(diphosphane)L2 (II) complexes in which L = N1-alkylated benzimidazoles, bonding to the metal through nitrogen, have been synthesized and characterized. In case 1-methylbenzimidazole, resulting exist as statistical mixtures all possible conformational isomers. When size substituent on benzimidazole was increased could be prepared that a single diastereomer. All possessing ligands bound ruthenium center are active for mild chemoselective hydrogenation ketones presence alkenes. Catalysts diastereomer, with enantiomerically pure diphosphanes, catalyze prochiral moderate levels enantioselectivity significantly improved relative catalysts existing several conformations.