1-Naphthyl-1,2-ethanediol as a new chiral modifier of platinum in the enantioselective hydrogenation of activated ketones

1-Naphthyl-1,2-ethanediol (NED) is shown to be a useful modifier in the hydrogenation of ketopantolactone and ethyl-4,4,4-trifluoroacetoacetate under mild conditions. It represents the first effective chiral nonamine-type modifier of Pt for the enantioselective hydrogenation of activated ketones. The enantio-differentiation is attributed to substrate–modifier interactions involving hydrogen bonding between the keto-carbonyl O atom and one or two OH groups of NED. Prominent nonlinear behavior was observed when mixtures of (S)-NED and (R)-2-(1-pyrrolidinyl)-1-(1-naphthyl)ethanol {(R)-PNE} were applied as chiral modifiers. The phenomenon is traced to stronger adsorption of PNE on the metal surface, despite the identical “anchoring moiety” (naphthalene ring) of the two modifiers.