Asymmetric transfer hydrogenation of C=O and C=N bonds by tethered Rh-III catalysts

Rh-III catalysts containing a tetramethylcyclopentadienyl group linked by a 'tether' to a tosylated diamine ligand have previously been reported by our group for the asymmetric transfer hydrogenation (ATH) of ketones. The extension of these catalysts to the asymmetric reduction of imines, as well as to more highly functionalized substrates is reported. In some cases, the catalysts give better ee values than other methods for these transformations at lower catalyst loadings. The introduction of a methoxy group into the tethering aryl ring does not negate the performance of the catalyst, thus opening up a route to supported derivatives.