ChemInform Abstract: Rapid, Productive and Stereoselective Hydrogenation of Ketones

Abstract

RuCl2(phosphine)2(1,2-diamine) complexes act as excellent precatalysts for homo- geneous hydrogenation of simple ketones which lack any functionality capable of interacting with the metallic center. This newly devised catalytic system allows preferential saturation of a CaO function over a coexisting CaC linkage in 2-propanol containing an alkaline base. Furthermore, the stereoselectivity of the reaction is easily controlled by the electronic and steric properties (bulkiness and chirality) of the ligands as well as the reaction conditions. Selective reduction of carbonyl compounds to alcohols has relied heavily on the use of metal hydride reagents. Our goal is to replace such stoichiometric reductions by catalytic hydrogenation, because the latter is obviously more beneficial, particularly for large-scale reactions. Here we describe a very practical homogeneous hydrogenation of ketones catalyzed by RuCl2(phosphine)2(1,2-diamine) and an inorganic base. The precatalysts can be preformed or generated in situ by mixing the phosphine-RuCl2 complex and an appropriate 1,2-diamine in 2-propanol. The reaction is normally conducted at room temperature and at < 8 atm of hydrogen. The new method shows promise for the synthesis of a wide range of achiral and chiral alcohols from ketonic substrates. This chemistry is entirely different from the BINAP-Ru catalyzed asymmetric hydrogenation of functionalized ketones developed earlier in our laboratories (1). RAPID HYDROGENATION OF SIMPLE KETONES