Search for: All records

Commercially available benzophenone imine (HNCPh 2 ) reacts with β-diketiminato copper( ii ) tert -butoxide complexes [Cu II ]–O t Bu to form isolable copper( ii ) ketimides [Cu II ]–NCPh 2 . Structural characterization of the three coordinate copper( ii ) ketimide [Me 3 NN]Cu–NCPh 2 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 ]–NCPh 2 readily capture alkyl radicals R˙ (PhCH(˙)Me and Cy˙) to form the corresponding R–NCPh 2 products in a process that competes with N–N coupling of copper( ii ) ketimides [Cu II ]–NCPh 2 to form the azine Ph 2 CN–NCPh 2 . Copper( ii ) ketimides [Cu II ]–NCAr 2 serve as intermediates in catalytic sp 3 C–H amination of substrates R–H with ketimines HNCAr 2 and t BuOO t Bu as oxidant to form N -alkyl ketimines R–NCAr 2 . This protocol enables the use of unactivated sp 3 C–H bonds to give R–NCAr 2 products easily converted to primary amines R–NH 2 via simple acidic deprotection. 

Abstract Undirected C(sp³)−H functionalization reactions often follow site‐selectivity patterns that mirror the corresponding C−H bond dissociation energies (BDEs). This often results in the functionalization of weaker tertiary C−H bonds in the presence of stronger secondary and primary bonds. An important, contemporary challenge is the development of catalyst systems capable of selectively functionalizing stronger primary and secondary C−H bonds over tertiary and benzylic C−H sites. Herein, we report a Cu catalyst that exhibits a high degree of primary and secondary over tertiary C−H bond selectivity in the amidation of linear and cyclic hydrocarbons with aroyl azides ArC(O)N₃. Mechanistic and DFT studies indicate that C−H amidation involves H‐atom abstraction from R‐H substrates by nitrene intermediates [Cu](κ²‐N,O‐NC(O)Ar) to provide carbon‐based radicals R^.and copper(II)amide intermediates [Cu^II]‐NHC(O)Ar that subsequently capture radicals R^.to form products R‐NHC(O)Ar. These studies reveal important catalyst features required to achieve primary and secondary C−H amidation selectivity in the absence of directing groups.