Iridium(III)-Catalyzed Enantioselective Si−H Bond Insertion and Formation of an Enantioenriched Silicon Center

Abstract

Iridium(III)-salen complexes were found to efficiently catalyze enantioselective carbene Si-H bond insertion. Highly enantioselective Si-H insertion with alpha-alkyl-alpha-diazoacetates (>or=97% ee) was achieved for the first time by using the iridium complex 4 {(aR,S), Ar = 4-TBDPSC(6)H(4)} bearing a concave-shaped salen ligand as the catalyst. Formation of a chiral silicon center was also achieved for the first time by the Si-H insertion into prochiral silanes: the reactions between prochiral silanes and tert-butyl alpha-diazopropionate in the presence of complex 5 {(aR,S), Ar = Ph} proceeded with high stereoselectivity (84-99% de, 94-->99% ee). The Si-H insertion into trisubstitued silanes with alpha-aryl-alpha-diazoacetates proceeded with almost complete enantioselectivity (>or=99% ee) by using complex 1 {(aR,R), Ar = Ph} as catalyst.