Pyrimidine Derivatives and Related Compounds, III / Synthesis of Some New Pyrazolo [1,5-a] pyrimidines and Pyrazolo [3,4-d] pyrimidine Derivatives

Abstract

Whereas β-cyanoethylhydrazine (1) reacts with the β-ethoxy-α,β-unsaturated nitriles (2a—c) to yield the 5-amino-1-B-cyanoethylpyrazoles (8a—c), 1 reacts with anilinomethylenemalononitrile (2d) to yield 3-amino-1-B-cyanoethyl-4-cyanopyrazole (4; R=H; X=CN). 3a readily cyclised into the 5-amino-6,7-dihydropyrazolo[1,5-a]pyrimidine derivative (6) by the action of ethanolic guanidine. 6 was readily converted into the oxo derivative (7) by the action of acetic acid. 7 was also obtained by the action of 1% NaOH on 3a. On the other hand, 3b afforded a mixture of the pyrazolo[1,5-a]pyrimidine derivative (8) and the carboxylic acid (9) when treated with 1% NaOH solution. 3-Aminocrotononitrile (2e) reacted with 1 to yield the hydrazone derivative (12). The latter derivative was converted into the pyrazolo[1,5-a]pyrimidine derivative (14) by the action of acetic acid. On the other hand, the hydrochloride (15) was formed on treatment of 12 with acetic acid hydrochloric acid mixture. Compounds 8 a, b reacted with carbon disulphide to yield the pyrazolo[3,4-d]-6 (7 H)-m- thiazinethione derivatives (16a,b). The latter were readily converted into the pyrazolo-[3,4-d]pyrimidine derivatives (17 a, b) by the action of aqueous NaOH solution.