Copper(ii) ketimides in sp3 C–H amination

Abstract

Commercially available benzophenone imine (HNCPh₂) reacts with β-diketiminato copper(II) tert-butoxide complexes [Cu^II]–O^tBu to form isolable copper(II) ketimides [Cu^II]–NCPh₂. Structural characterization of the three coordinate copper(II) ketimide [Me₃NN]Cu–NCPh₂ reveals a short Cu-N_ketimide distance (1.700(2) Å) with a nearly linear Cu–N–C linkage (178.9(2)°). Copper(II) ketimides [Cu^II]–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 [Cu^II]–NCPh₂ to form the azine Ph₂CN–NCPh₂. Copper(II) ketimides [Cu^II]–NCAr₂ serve as intermediates in catalytic sp³ C–H amination of substrates R–H with ketimines HNCAr₂ and ^tBuOO^tBu 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.