Theoretical research on the direct carboxylation of benzene with CO2 catalyzed by different carbene‐CuOH compounds

Abstract

AbstractThe direct carboxylation between the benzene C–H and CO2 is a long‐standing challenge in catalysis. Based on the known experimental process for the direct carboxylation of fluorobenzene, herein, a theoretical design of efficient carbene‐copper catalysts for the direct carboxylation of benzene was reported. It was found that the reaction included two steps: C–H bond breaking and CO2 insertion into Cu‐phenyl. C–H breaking is the rate‐determining step. To find out a more effective catalyst, totally, 16 carbene‐copper compounds with different electronic and steric structures were investigated. The energy barriers for the C–H bond breaking range from 104.2 to 153.7 kJ/mol. Two effective methods are proposed for improving the catalytic reactivity: reducing the electronically active substituent on carbene and introducing interaction to stabilize the transition state (TS). Based on these findings, adopting a well‐known (amino)(silyl)carbene modified by a –NH2 group gives the most effective catalyst for the direct carboxylation of benzene. Using –NH2 group can introduce two strong interactions (OOH···HNH2 and NNH2···Cu) during the formation of TS, which can greatly stabilize the structure of TS and dramatically reduce the energy barrier. The catalytic reactivity of the most effective carbene‐copper catalyst is comparable with the noble metal‐based ruthenium pincer carboxylate complexes.