III International Conference

PP-II-93on complex [Rh(cod) 2 ] + CF 3 SO - 3 as pre-catalysts in the presence of salts 2 are shown in theFigure. In the presence of optically active quaternary salt 2 the optical yield of S-(-)-2-phenylethanol is higher though the conversion is lower (Table).10,09,59,028,58,017,57,00 50 100 150 200 250Figure. Kinetic hydrogen transfer hydrogenation of acetophenone on complex 1 (1) and on[Rh(cod) 2 ]TfO in the presence of two equivalents of 2 (R = benzyl) (2) (С Rh = 1.1 mmol/L,KOH/Rh = 4, in i-PrOH at 80 о С)Table. Enantioselective hydrogen transfer hydrogenation of acetophenone on rhodium(I)complexes in i-PrOH (C Rh = 1.1 mmol/L, KOH/Rh = 3-5, 80 о С)No. Catalyst Substrate/Rh Chem.yield, % Optic. yield, TON%,(conf)1 1 98 20 6, S(-) 522 Rh(cod) 2 ]TfO + 2 80 7 16, S(-) 15In both cases the reduction of acetophenone is incomplete as a result of deactivation ofthe catalyst with time. Apparently, the catalytic activity is due to either metal complexes priorto reduction of Rh(1+) to Rh(0) or Rh(0)-containing particles of "quasihomogeneous" nature.With formation of larger particles the system is deactivated. The presence of optically activeproducts in the second case proves modification of active particles by compound 2 in thechirality transfer stage, which is possible if the process is catalyzed by particles stabilized byoptically active quaternary salt. Therefore, it may be concluded that hydrogenation ofacetophenone with hydrogen transfer proceeds both on molecular complexes containing chiraldiamines and on reduced metal rhodium particles gradually formed in the system under thereaction conditions.References1. [1] Nindakova L. O., Shainyan B. A., Albanov A. I. Russ. Chem. Bull. Int. Ed. 2001. V. 50. N 10.P. 1860-1864.2. [2] Widegren J. A., Finke R. G. J. Mol. Catal. A: Chemical. 2003. V. 198. N 2. P. 317–341.332