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A study on the enantioselective hydrogenation of tertiary alkyl ketones catalysed by a novel class of tridentate-Ru complex is reported. In contrast to the extensively studied [RuCl(2)(diphos)(di-primary amine)] complexes, this new class of hydrogenation catalyst smoothly reduces these less reactive bulky ketones with up to 94 % ee. The same catalyst system can also selectively reduce other potentially problematic substrates such as bulky heterocyclic ketones. Unusually for a pressure hydrogenation catalyst, similar enantioselectivity can be obtained under transfer hydrogenation conditions. The transfer hydrogenations are somewhat slower than the pressure hydrogenations, but this drawback is readily overcome, since we have discovered that a microwave accelerated transfer hydrogenation of the above ketones occurs within 20 min at about 90 degrees C with similar selectivity to that obtained in the pressure hydrogenation system.

Alcohols Q 0230Enantioselective Hydrogenation and Transfer Hydrogenation of Bulky Ketones Catalyzed by a Ruthenium Complex of a Chiral Tridentate Ligand. -The novel ruthenium complex (RTL) shows activity in both enantioselective pressure and transfer hydrogenation of ketones which do not react when established ketone hydrogenation catalysts are used. -(DIAZ-VALENZUELA, M. B.; PHILLIPS, S. D.; FRANCE, M. B.; GUNN, M. E.; CLARKE*, M. L.; Chem. Eur.

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