Benzoin condensation of aromatic aldehydes catalyzed by N-heterocyclic carbenes under mild conditions

Abstract

The benzoin condensation was used to evaluate the catalytic activity of different N-heterocyclic carbenes as a function of their structure and N-substituents. There is a correlation between the length of an N-alkyl substituent and its performance as an organocatalyst. Heteroaromatic aldehydes were found to be the most reactive, among the screened substrates, finishing the reaction in 30 minutes, with almost quantitative yields. On the other hand, p-nitrobenzaldehyde, a strongly electrophilic aldehyde, was the …