Carboxylation of NH/CH Bonds Using N‐Heterocyclic Carbene Copper(I) Complexes

Abstract

Greenhouse gas makes good: A simple copper‐mediated protocol has been developed where NH or CH bonds can be directly functionalized using an easily prepared catalyst. The novel [1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene]copper(I) hydroxide, [Cu(IPr)(OH)], permits the facile activation and carboxylation of NH and CH bonds with pKa values of less than 27.7 (see scheme).

Polynuclear Copper(I) Complexes with Chelating Bis‐ and Tris‐N‐Heterocyclic Carbene Ligands: Catalytic Activity in Nitrene and Carbene Transfer Reactions

“…In this context, the instability of copper(I)-NHC complexes towards air oxidation has very recently been reported. [13,21] Catalytic Activity: Nitrene Transfer Reactions…”

Copper–NHC complexes in catalysis

“…This new species was first used as a synthon for the synthesis of [Cu(R)(IPr)] derivatives via stoichiometric C-H activation. These initial studies were followed by the use of the hydroxide derivative as a powerful catalyst for direct carboxylation of N-H and C-H bonds (Scheme 3.1.1) [94]. The complex showed high selectivity for N-H and C-H bonds (with a pK a below 27.7).…”

Direct Carboxylation of C(sp3)-H and C(sp2)-H Bonds with CO2 by Transition-Metal-Catalyzed and Base-Mediated Reactions

“…Nolan noted that mechanistic features of the Au(I)-catalyzed carboxylation reaction (shown in Scheme 40) are similar to the generally accepted mechanism of the copper(I)-catalyzed carboxylation of organoboronic esters [30,119]. The Further development of the abovementioned study led to the carboxylation of oxazole, benzoxazole, benzothiazole, and polyfluorobenzenes with CO 2 by employing the cheaper [(IPr)CuOH] catalyst [56] Further development of the abovementioned study led to the carboxylation of oxazole, benzoxazole, benzothiazole, and polyfluorobenzenes with CO2 by employing the cheaper [(IPr)CuOH] catalyst [56] in the presence of CsOH (2.2 eq.) under low CO2 pressure (0.15 MPa) at the temperature of 65 °C (Scheme 41).…”

“…Interestingly, several reports [56,57,61] describe the employment of metal complexes bearing OH − or t BuO − ligands acting as proton acceptors during the catalytic cycle (an example is reported in Scheme 2d [57]) (see Section 5.2). These efficient synthetic methods can be "formally" considered as processes in which a base-promoted reaction takes place with the assistance of a metal catalyst.…”