Unexpected Products from the Biginelli Reactions of 3-Amino-1,2,4-triazole

Significance

Reported is the condensation of 3-amino-1,2,4-triazole (3) with substituted sali­cylaldehydes 1 and methyl acetoacetate 2 under Biginelli conditions. Surprisingly, the expected triazolopyrimidine products 4 and 5 of this reaction were not observed; rather the oxaspirocyclic systems 6 and 7 were obtained in diastereoselective fashion. Attempts to achieve this transformation with substituted salicylaldehydes bearing electron-withdrawing groups (e.g., NO₂) failed; however, electron-donating substituents were well tolerated.