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The importance of four-membered NHCs in stabilizing Breslow intermediates on benzoin condensation pathway. | LitMetric

AI Article Synopsis

  • - N-heterocyclic carbenes (NHCs) are effective organocatalysts used in reactions like benzoin condensation, where a compound called the Breslow intermediate (BI) plays a key role.
  • - New four-membered NHCs are specifically being studied for their potential catalytic abilities by analyzing the potential energy surface (PES) of the benzoin condensation reaction compared to five-membered NHCs.
  • - While the energy barrier for forming the Breslow intermediate is similar for both four-membered and five-membered NHCs, the four-membered NHCs show a significantly higher energy barrier in the second step required for completing the benzoin reaction, suggesting they make it harder to proceed

Article Abstract

N-heterocyclic carbenes (NHCs) have been established to be effective organocatalysts for facilitating the benzoin condensation and many other reactions. These reactions involve the formation of a Breslow intermediate (BI), which exhibits umpolung chemistry. To facilitate organocatalysis, several new cyclic carbenes are being introduced, four-membered NHCs are of special interest. Whether these NHCs can exhibit catalytic influence or not, can be evaluated by exploring the potential energy surface (PES) of the benzoin condensation reaction. Quantum chemical analysis has been carried out to compare the PES of these four-membered NHCs with that of standard five-membered NHCs to explore their catalytic ability. The barrier for the first step of the reaction for the formation of BI is comparable in all the cases. But the barrier for the second step of the reaction leading to the benzoin formation from BI is estimated to be very high for the four membered NHCs. These results indicate that the probability of identifying and isolating the BI is very high in comparison to the completion of benzoin condensation reaction in the case of the four-membered NHCs.

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http://dx.doi.org/10.1002/jcc.26935DOI Listing

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