A Convenient One-Pot Synthesis of Pyrazolo[3,4-d]pyrimidines and s-Triazolo[3,4-b][1,3,5]thiadiazines

The reaction of 5-amino-3-aryl-1-phenylpyrazoles (1a-d) with formaldehyde and secondary amines in boiling ethanol gave the corresponding 4-alkylaminomethyl derivatives (2a-f) and bis-(4-pyrazolyl)methane (4a,b) as byproduct. Such reaction with primary aliphatic and aro­ matic amines at room temperature afforded 1,3,5-trisubstituted (5a-h) and 1,3.5,7-tetrasubstituted tetrahydropyrazolo[3,4-d]pyrimidines (8a-k) respectively in good yield. Similarily, the Mannich reaction of 5-mercapto-3-phenyl-1,2,4-triazole (9) with secondary amines, in boiling ethanol, and primary aromatic amines, at room temperature, gave 2 -substituted aminomethyl derivatives (10a-c) and (14a-g) respectively,while with primary aliphatic amines, p-toluidine and p-anisidine,at room temperature,and with other primary aromatic amines, in boiling ethanol, afforded the cyclized products 12,4-triazolo[3,4-b]thiadiazines (13a-e); (15f,g) and (15a-e), respectively.