P-chiral β-aminophosphine oxides vs. β-aminophosphines as auxiliaries for ruthenium catalysed enantioselective transfer hydrogenation of arylketones

Abstract Enantiopure P-chiral β-aminophosphine oxides and the corresponding β-aminophosphines have been synthesised and used as chiral auxiliaries in ruthenium catalysed asymmetric transfer hydrogenation of arylketones producing optically active alcohols up to 80% ee. Both types of auxiliaries provide comparable induction levels but the β-aminophosphine oxide ligands induce higher catalytic activities generally. In some experiments, when changing the achiral arene ligand in the catalyst precursor, a peculiar reversal of the product configuration was observed.