By the use of an N-heterocyclic carbene copper(I) complex as a catalyst, the boracarboxylation of various alkynes (e.g., diaryl alkynes, aryl/alkyl alkynes, and phenylacetylene) with a diborane compound and carbon dioxide has been achieved for the first time, affording the α,β-unsaturated β-boralactone derivatives regio- and stereoselectively via a borylcupration/carboxylation cascade. Some important reaction intermediates were isolated and structurally characterized to clarify the reaction mechanism.

Cooking with gas: Copper complexes serve as excellent catalysts for the direct carboxylation of aromatic heterocyclic CH bonds with CO2, thereby offering an economical and environmentally benign process for the synthesis of heterocyclic carboxylic esters (see scheme; IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene). Some active intermediates of this reaction have been isolated and structurally characterized.

The N-heterocyclic carbene-copper alkoxide complex [(IPr)Cu(OtBu)] acts as a highly efficient catalyst for the hydrosilylation of carbon dioxide with a hydrosilane. The desired product, silyl formate could be isolated in multigram quantity under solvent free conditions. A copper formate catalyst intermediate was successfully isolated and structurally characterized, thus offering important insight into the mechanistic details.

This minireview gives an overview of the chemical transformations of carbon dioxide (CO 2 ) catalysed by N-heterocyclic carbene (NHC)-copper complexes. NHC-copper complexes can serve as excellent catalysts for the carboxylation of various substrates with CO 2 and the reduction of CO 2 to CO or formic acid derivatives. In addition, NHC ligands enable the isolation of structurally characterisable key reaction intermediates, thus helping in understanding the mechanistic details of the catalytic processes. The related reactions catalysed by other metal complexes with NHC ligands are also briefly described.