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Many organic and main-group compounds, usually acids or bases, can accelerate chemical reactions when used in substoichiometric quantities, a process known as organocatalysis. In marked contrast, very few of these compounds are able to activate carbon monoxide, and until now, none of them could catalyze its chemical transformation, a classical task for transition metals. Herein we report that a stable singlet ambiphilic carbene activates CO and catalytically promotes the carbonylation of an o -quinone into a cyclic carbonate. These findings pave the way for the discovery of metal-free catalyzed carbonylation reactions.

It has been previously demonstrated that stable singlet electrophilic carbenes can behave as metal surrogates in the activation of strong E-H bonds (E = H, B, N, Si, P), but it was believed that these activations only proceed through an irreversible activation barrier. Herein we show that, as is the case with transition metals, the steric environment can be used to promote reductive elimination at carbon centers.

Cyclic (alkyl)(amino)carbenes with a six-membered backbone were prepared. Compared to their five-membered analogues, they feature increased % V bur and enhanced donor and acceptor properties, as evidenced by the observed n → π* transition trailing into the visible region. The high ambiphilic character even allows for the intramolecular insertion of the carbene into an unactivated C(sp 3 )-H bond. When used as ligands, they outcompete the five-membered analogues in the palladium-mediated α-arylation of ketones with aryl chlorides.