THE REACTION OF BENZOYL-SUBSTITUTED HETEROCYCLIC KETENE AMINALS WITH ARYL AZIDES

The reaction between heterocyclic ketene animals, 2-(benzoylmethylene)imidazolidines 3, -hexahydropyrimidines 4, and phenyl azides 5 was investigated. Both the reaction rate and products were strongly dependent on the substituents on 3 or 4 and 5. The reaction rate decreased with the decrease of the electron-withdrawing ability of the Y on the aryl azide 5 with the order NO2 > Cl > H > CH3O, as well as with the decrease of the electron-donating ability of the X on the 3 or 4 following the order CH3O > CH3 > H > Cl. Substituents X and Y affected the course of the reaction. Thus, 3 or 4 reacted with p-nitrophenyl azide 5a to give exclusively highly substituted 1,2,3-triazole derivatives 6aa-da and 7aa-da. The reaction between 3 or 4 and other aryl azides 5b-d afforded respectively fused triazoles 8a-d or 9a-d (6-31%) in addition to triazoles 6ab-bd or 7ab-bd (8-76%). It is concluded that 3 and 4 behave mostly as nucleophiles rather than 1,3-dipolarophiles in reaction with aryl azides 5. Only in the case of unfavorable electronic factors may 3 and 4 act as 1,3-dipolarophiles toward 5.