N‐Heterocyclic Carbene‐Catalyzed Umpolung Reactions of Imines Proceeding Through Aza‐Breslow Intermediates

N‐heterocyclic carbenes (NHCs) have emerged as efficient catalysts for promoting umpolung reactions of aldehydes and enals. Recently, the NHCs have been successfully used for catalyzing the umpolung reactions of aldimines through the formation of aza‐Breslow intermediates. This article provides a systematic review of the research progress in the polarity reversal of imines and related reactions catalyzed by NHCs, along with a detailed discussion and summary of the underlying reaction mechanisms. The review is organized and categorized according to the types of NHC‐catalyzed reactions involving imines.