Copper(ii) ketimides in sp3 C–H amination†
Commercially available benzophenone imine (HNCPh2) reacts with β-diketiminato copper(II) tert-butoxide complexes [CuII]–OtBu to form isolable copper(II) ketimides [CuII]–NCPh2. Structural characterization of the three coordinate copper(II) ketimide [Me3NN]Cu–NCPh2 reveals a short Cu-Nketimide distance (1.700(2) Å) with a nearly linear Cu–N–C linkage (178.9(2)°). Copper(II) ketimides [CuII]–NCPh2 readily capture alkyl radicals R˙ (PhCH(˙)Me and Cy˙) to form the corresponding R–NCPh2 products in a process that competes with N–N coupling of copper(II) ketimides [CuII]–NCPh2 to form the azine Ph2CN–NCPh2. Copper(II) ketimides [CuII]–NCAr2 serve as intermediates in catalytic sp3 C–H amination of substrates R–H with ketimines HNCAr2 and tBuOOtBu as oxidant to form N-alkyl ketimines R–NCAr2. This protocol enables the use of unactivated sp3 C–H bonds to give R–NCAr2 products easily converted to primary amines R–NH2via simple acidic deprotection.