Catalytic sugar-assisted transfer hydrogenation with Ru(II), Rh(III) and Ir(III) halfsandwich complexes

The application of halfsandwich ruthenium(II), rhodium(III) and iridium(III) complexes of four different methyl 2,3-diamino-4,6-O-benzylidene-2,3-dideoxy-alpha-D-hexopyranosides and a methyl 2-amino-3-tosylamido-alpha-D-glucopyranoside as catalyst precursors in asymmetric transfer hydrogenation of acetophenone is reported. The configuration of the hexopyranosides and the type of arene ligands determine the formation of R- or S-1-phenylethanol up to 66% ee. A large influence of the substitution pattern of the arene ligands on the extent of the enantiomeric excess is demonstrated. The results are interpreted by means of DFT calculations. (C) 2015 Elsevier B.V. All rights reserved.