A detailed study of the scope of the amidine Diels-Alder reaction with 1, 3, 5-triazines is described. The thermal reaction of amidines with symmetrical 1, 3, 5-triazines proceeds with in situ amidine to 1, l-diaminoethene tautomerization,[4+ 21 cycloaddition with the 1, 3, 5- triazine, loss of ammonia from the initial Diels-Alder adduct with imine generation, imine to enamine tautomerization, and retro Diels-Alder loss of ethyl cyanoformate to provide ...