Synthesis and antihypertensive activity of novel 1-(4-benzyl-1-phthalazinyl)-pyrazolo{[}3,4-d]pyrimidines

Convenient Syntheses of derivatives of the pyrazolo{[}3,4-d]pyrimidines from 1-(4-benzyl-1-phthalazinyl)-3-amino-4-cyano-5-methylpyrazole (1) and carbon disulphide, aryl isothiocyanates, nitriles or guanidine are described. Derivatives of compound 1 undergo cyclization to the titled ring system by action of dimethylformamide dimethylacetal or hydrogen sulphide followed by treatment with triethylamine. Some of the new compounds were studied as antihypertensive agents.