Hydrosilylation of acetophenone with diphenylsilane in the presence of rhodium(I) complexes with chiral amines

Abstract

New chiral rhodium complexes cis-[Rh(CO)2(RNH2)Cl] [RNH2 = (R)-(−)-cis-MyrtNH2, (R)-(−)-MenthylNH2, (R)-(+)-BornylNH2] were synthesized and their catalytic properties in reactions of hydrosilylation of acetophenone with diphenylsilane were studied. It was shown that the reaction products were diphenyl-1-phenylethoxysilane, diphenyl-1-phenylvinyloxysilane and 1,1,3,3-tetraphenyldisiloxane. The best catalytic activity displayed (−)-cis-[Rh(CO)2(MenthNH2)Cl]. The hydrosilylation of acetophenone with diphenylsilane in the presence of [Rh(CO)2(μ-Cl)]2 and [Rh(cod)Cl]2 and amines in situ was studied. The best ratio amine:complex = 5:1 was established. With the catalytic systems based on [Rh(cod)Cl]2 or [Rh(CO)2(μ-Cl)]2 the activity increased in the series of amines: (R)-(−)-cis-MyrtNH2 < (R)-(−)-MenthylNH2 < (R)-(+)-BornylNH2, and (R)-(−)-MenthylNH2 < (R)-(+)-BornylNH2 < (R)-(−)-cis-MyrtNH2, respectively. The chemoselectivity maximum was observed in the presence of [Rh(cod)Cl]2 with (R)-(−)-MenthylNH2 and [Rh (CO)2(μ-Cl)]2 with (R)-(+)-BornylNH2; maximum asymmetric induction was 43.5% ee at the use of [Rh(CO)2 (μ-Cl)]2 and (R)-(+)-BornylNH2.