Rhodium-Catalyzed Chemo- and Enantioselective Hydrogenation of Alkynyl-Aryl Hydrazones

As an update of our continuous interest in the hydrogenation of hydrazones, a chemo- and enantioselective hydrogenation of alkynyl-aryl hydrazones was developed using a rhodium complex [Rh((R,Sp)-JosiPhos)(cod)]SbF6 as the catalyst and benzoic acid as an additive. Directed by a p-nitrobenzamido group, the chiral propargyl hydrazines, which can be easily converted to chiral propargylamines of significant importance and potential use, were obtained with good yields, excellent chemoselectivities and good to excellent enantioselectivities. Although the enantioselectivity of the reaction and the substrate/catalyst ratio require further refinement, the reported methodology provides an alternative route for the efficient preparation of chiral propargylamines.