Studies on the Synthesis of New 3‐(3,5‐Diamino‐1‐substituted‐pyrazol‐4‐yl)azo‐thieno[2,3‐ b ]pyridines and 3‐(2‐Amino‐5,7‐disubstituted‐pyrazolo[1,5‐ a ]pyrimidine‐3‐yl)azothieno[2,3‐ b ]pyridines

Coupling the diazonium salt of 3‐amino‐2‐cyano‐4,6‐dimethylthieno[2,3‐ b ]pyridine 1 with malononitrile 2 gave 2‐cyano‐3‐(hydrazonomalononitrile)‐4,6‐dimethylthieno[2,3‐ b ]pyridine 3 which then reacted with hydrazine compounds 4a‐4h to yield corresponding 2‐cyano‐3‐(3,5‐diamino‐1‐substituted‐pyrazol‐4‐yl)azo‐4,6‐dimethylthieno[2,3‐ b ]pyridines 5a‐5h. The 2‐cyano‐3‐(2‐amino‐5,7‐disubstituted‐pyrazolo‐[1,5‐ a ]pyrimidine‐3‐yl)azo‐4,6‐dimethylthieno[2,3‐ b ]pyridines 7a‐7f were obtained in good yield by the cyclocondensation reaction of 2‐cyano‐3‐(3,5‐diamino‐pyrazol‐4‐yl)azo‐4,6‐dimethylthieno[2,3‐ b ]pyridine 5a with the appropriate 1,3‐diketones 6a‐6f under acidic condition.