Catalytic cyclization of amides of ethenetricarboxylate bearing ether and acetal groups has been examined. The reaction of the amides bearing cyclic ether and acetal groups in the presence of Lewis acid such as Sc(OTf) gave spirocyclic piperidine derivatives as major products. The cyclized products may be formed via intramolecular hydride transfer. The reaction mechanism was examined by the DFT calculations. The scope and limitations of the hydride transfer/cyclization reactions of amides of ethenetricarboxylates was investigated, and morpholine formation by intramolecular oxy-Michael addition was also found.

The cyclization of amides derived from ethenetricarboxylic acid bearing tert‐amino groups has been examined. The amides were efficiently converted to piperidine derivatives (2‐piperidones) upon heating in a polar solvent (e. g., DMSO or DMF) via intramolecular hydride transfer and subsequent ring closure. The reaction was less efficient in the presence of a Lewis acid. The reactivity varies depending on the alkyl substituents of tert‐amino groups, probably due to steric effects. The hydride transfer/cyclization mechanism was investigated by DFT calculations. The reaction of the carboxylic acid and relatively bulky diamines such as diisopropyl‐substituted diamine in the presence of amide condensation reagents at 60 °C gave the piperidine derivatives in a one‐pot reaction. The reaction of the diisopropylamine substituted piperidine product with primary amines gave secondary amine‐substituted piperidines.