A synthesis of some novel 4,5-dihydroazepines by the reaction of oxazolium 5-oxides with 1,2-dicyanocyclobutene†

Heating primary or secondary α-amino acids in acetic anhydride in the presence of 1,2-dicyanocyclobutene leads to 4,5-dihydroazepines via the intermediacy of mesoionic oxazolium 5-oxides.