Unexpected ring size effect of the annulation reaction of heterocyclic secondary enamines with dicarboxylic acid dichlorides

Heterocyclic enamines are versatile ambident nucleophilic reagents able to react with both aliphatic and aromatic dicarboxylic acid dichlorides in diverse manners. The reaction outcome was strongly dependent upon the heterocyclic structure of the enamines and the nature of the diacid dichlorides employed.