Hydrogenation of imines by rhodium-phosphine complexes

Catalytic Hydrogenation of α‐Iminophosphonates as a Method for the Synthesis of Racemic and Optically Active α‐Aminophosphonates

“…The reduction of Me-subsituted a-iminophosphonate 2c gave a-aminophosphonate 3c* in quantitative yield and 94% ee after 6 h. The hydrogenation rate of a-iminophosphonates 2d, f containing more p-donor aromatic substituents at the a-C atom decreases noticeably, which is consistent with the mechanism proposed earlier, [63,65] including the hydride transfer from Rh to the a-C atom of h 2 -(C=N)-coordinated imine with formation of the Rh À N bond. The completion of the reaction in the case of fluorine-substituted a-iminophosphonate 2d requires 10 h, the enantiomeric excess being 75%.…”

Rhodium and iridium complexes containing diphenyl-2-(3-methyl)indolylphosphine: synthesis, structure and application in the catalytic transfer hydrogenation of ketones

“…The corresponding complexes containing two of the phosphine ligands, [Rh(COD)L 2 ]BF 4 (6) and [Ir(COD)L 2 ]BF 4 (7), were readily prepared by a two step procedure (Scheme 3). The chloride ligand was removed from complexes 1 and 2 by addition of AgBF 4 to their dichloromethane solutions.…”

“…5 We became interested in this reaction as a means of exploring a potential cooperation effect from the close proximity of certain functional groups to the metal centre. 6 In the Noyori systems, the coordination of an NH functional group at the metal centre is key in determining the enhanced activities. 7 We were interested to explore whether any cooperation effect would result from the presence of an NH functional group in close proximity to the metal centre.…”

“…In principle, the NH group would stabilize resulting hydride species, perhaps via hydrogen bonding interactions 8 or provide a means of directing substrates towards the metal centre. 6 We therefore set out to prepare some group nine complexes containing the relatively unexplored ligand, diphenyl-2-(3-methyl)indolylphosphine (L) (Fig. 1).…”

Catalytic Enantioselective Addition to Imines

“…When a preformed catalyst was used, the reaction proceeded quantitatively, but no chiral induction was observed (Table , entry 6). According to the reaction mechanism of the Rh-mediated hydrogenation suggested by Longley and Wilkinson et al, oxidative addition of hydrogen to rhodium(I) is the first step of the reactions . On the other hand, James et al suggested that coordination of nitrogen atoms of imines to the rhodium center was the first step of the reactions 32b.…”