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

Iridium(III)-salen complexes were found to efficiently catalyze enantioselective carbene Si−H bond insertion. Highly enantioselective Si−H insertion with α-alkyl-α-diazoacetates (≥97% ee) was achieved for the first time by using the iridium complex 4 {(aR,S), Ar = 4-TBDPSC6H4} 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 α-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 α-aryl-α-diazoacetates proceeded with almost complete enantioselectivity (≥99% ee) by using complex 1 {(aR,R), Ar = Ph} as catalyst.