Asymmetric hydrogenation reactions with Rh and Ru complexes bearing phosphine-phosphites with an oxymethylene backbone

Abstract

Phosphine-phosphites 3a and 3b, derived from diphenylhydroxymethyl phosphine have been prepared. From these ligands [Rh(COD)(3a)]BF4 5a and RuCl2(3b)[(S,S)-DPEN] 6b (DPEN = 1,2-diphenylethylenediamine) were synthesized and their structure determined by X-ray diffraction. Ligands 3 are characterized by a small bite angle of 83°. In addition, 5a led to an active catalyst for the hydrogenation of olefins, giving enantioselectivities of up to 96% ee. Likewise, compound 6b showed good activity and enantioselectivity in the hydrogenation of N-1-phenyl ethylidene aniline and a completed reaction at S/C = 500 in 24 h with 83% ee.