Françoise Cado, Jean Pierre Bazureau, Jack Hamelin, Patrick Jacquault and Marie-Joëlle Dozias
The reaction of ethyl 1H-perimidine-2-acetate 3 as a heterocyclic ketene-aminal with 2.1 equiv. of ethyl propiolate 4a or but-3-yn-2-one 4b affords new fused perimidines in good yields by a tandem C-addition/hetero Diels–Alder reaction; the new 1-azabuta-1,3-diene intermediates are generated in situ from the initial trans C-addition products by thermal 1,5-prototropy.