Fused Pyrimidines. IV. Synthesis of 3-Alkyl (or Acyl)-aminopyrazolo [3, 4-d] pyrimidine Derivatives from 6-Hydrazinouracils and Isothiocyanates

Abstract

1, 3-Dialkyl-6-hydrazinouracils (I) reacted with alkyl and acyl isothiocyanates to yield 5, 7-dialkyl-3-alkyl (or acyl) aminopyrazolo [3, 4-d] pyrimidine-4, 6 (5H, 7H)-diones (II). This reaction was investigated in detail and it was found that the first product was a 6-[4-alkyl (or acyl) thiosemicarbazido] uracil (IV), which cyclized to II through two pathways. Acylation of II afforded the corresponding 2-acyl derivatives. Treatment of 1, 3-diethyl-6-hydrazinouracil (Ia) with phosgeneimmonium chloride afforded 5, 7-diethyl-3-dimethylamino [3, 4-d] pyrimidine-4, 6 (5H, 7H)-dione (X).