Copper(ii) ketimides in sp3 C-H amination

Isuri U Jayasooriya; Abolghasem Gus Bakhoda; Rachel Palmer; Kristi Ng; Nour L Khachemoune; Jeffery A Bertke; Timothy H Warren

doi:10.1039/d1sc01990b

Copper(ii) ketimides in sp³ C-H amination

Chem Sci. 2021 Nov 5;12(47):15733-15738. doi: 10.1039/d1sc01990b. eCollection 2021 Dec 8.

Authors

Isuri U Jayasooriya¹, Abolghasem Gus Bakhoda¹, Rachel Palmer¹, Kristi Ng¹, Nour L Khachemoune¹, Jeffery A Bertke¹, Timothy H Warren¹

Affiliation

¹ Department of Chemistry, Georgetown University Box 571227-1227 Washington DC 20057 USA [email protected].

Abstract

Commercially available benzophenone imine (HN[double bond, length as m-dash]CPh₂) reacts with β-diketiminato copper(ii) tert-butoxide complexes [Cu^II]-O ^t Bu to form isolable copper(ii) ketimides [Cu^II]-N[double bond, length as m-dash]CPh₂. Structural characterization of the three coordinate copper(ii) ketimide [Me₃NN]Cu-N[double bond, length as m-dash]CPh₂ 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[double bond, length as m-dash]CPh₂ readily capture alkyl radicals R˙ (PhCH(˙)Me and Cy˙) to form the corresponding R-N[double bond, length as m-dash]CPh₂ products in a process that competes with N-N coupling of copper(ii) ketimides [Cu^II]-N[double bond, length as m-dash]CPh₂ to form the azine Ph₂C[double bond, length as m-dash]N-N[double bond, length as m-dash]CPh₂. Copper(ii) ketimides [Cu^II]-N[double bond, length as m-dash]CAr₂ serve as intermediates in catalytic sp³ C-H amination of substrates R-H with ketimines HN[double bond, length as m-dash]CAr₂ and ^t BuOO ^t Bu as oxidant to form N-alkyl ketimines R-N[double bond, length as m-dash]CAr₂. This protocol enables the use of unactivated sp³ C-H bonds to give R-N[double bond, length as m-dash]CAr₂ products easily converted to primary amines R-NH₂ via simple acidic deprotection.