.7 - Chloro-1, 2,4 - Triazolo [1,5-c] Pyrimidine Derivatives

The structures and applications of common five-numbered heterocycle-fused pyrimidines were reviewed in this thesis. The synthetic ways to [1,2,4]triazolo[1,5-c]pyrimidines were summarized. Four new compounds of 7-chloro[1,2,4]triazolo[1,5-c]pyrimidine analogues, with good scientific value and potential economic value in organic synthesis, were designed and synthesized. The key intermediate 4,6-dichloropyrimidine was synthesized starting from the low-cost readily available dimethyl malonate through a non-patent protection process. The procedure involved cyclization and chlorination. 7-Chloro-2-methyl[1,2,4]triazolo[1,5-c]pyrimidine as a model compound was synthesized by two synthesis routes starting from 4,6-dichloropyrimidine. The versatility of the synthetic process of 7-chloro-2-methyl[1,2,4]triazolo[1,5-c] pyrimidine and reactivity of 7-chloro[1,2,4]triazolo[1,5-c]pyrimidine analogues designed were preliminarily studied. For the first route, 4-chloro-6-hydrazinylpyrimidine was obtained in>90% yield for the reaction between 4,6-dichloropyrimidine and 85% hydrazine hydrate, and 7-chloro-2-methyl[1,2,4]triazolo[1,5-c]pyrimidine was obtained in>90% yield for the reaction of 4-chloro-6-hydrazinylpyrimidine and trimethyl orthoacetate.In the second route,4,6-dichloropyrimidine was reacted with hydrazide to give N'-(6-chloropyrimidin-4-yl)acetohydrazide in>80% yield, which was then treated with POCl3 to afford 7-chloro-2-methyl[1,2,4]triazolo[1,5-c]pyrimidine in>50% yield. This process involved ring-closure reaction and Dimroth rearrangement. The second route was further optimized to one-pot operation:the reaction of 4,6-dichloropyrimidine and acetohydrazidewas continued for 12 hours, then POCl3 was added, and the reaction solution was refluxing 2 hours. After workup, 7-chloro-2-methyl[1,2,4]triazolo[1,5-c]pyrimidine was obtained in>50% yield. Three 7-chloro[1,2,4]triazolo[1,5-c]pyrimidine analogues were prepared according to the second synthesis route with>50% yields. A small compound library from 7-chloro[1,2,4]triazolo[1,5-c]pyrimidines and amines (aniline and benzylamine) indicated the good utility of this class of heterocylic intermediates.