Isolation of bis(copper) complexes that are kinetically more active than their mononuclear counterparts in the most popular “click chemistry” reaction.
Cyclic (alkyl)(amino)carbenes with a six-membered backbone were prepared. Compared to their five-membered analogues, they feature increased % V 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)-H bond. When used as ligands, they outcompete the five-membered analogues in the palladium-mediated α-arylation of ketones with aryl chlorides.
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.
A novel synthetic route gives access to mesoionic carbene and cyclopropenylidene supported gold chloride complexes. The corresponding cationic MIC-gold complex obtained by chloride abstraction allows for the first transition metal-catalyzed functionalization of both nitrogens of parent hydrazine.
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 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 ortho-quinone into a cyclic carbonate. These findings pave the way for the discovery of metal-free catalyzed carbonylation reactions.
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