5‐(1‐Pyrrolyl)‐2‐Phenylthieno[2,3‐ d ]Pyrimidine as Building Block in Heterocyclic Synthesis: Novel Synthesis of Some Pyrazoles, Pyrimidines, Imidazo[1,2‐ a ]Pyrimidines, Pyrazolo[1,5‐ a ]Pyrimidines, Pyrido‐(Pyrimido)Pyrazolo[1,5‐ a ]Pyrimidines, 1,2,4‐Triazolo[1,5‐ a ]Pyrimidine and a 1,2,3,4‐Tetrazolo[1,5‐ a ]Pyrimidine Derivative

Abstract Treatment of enaminone derivative 6‐(3‐dimethylamino‐acryloyl)‐5‐(1‐pyrrolyl)‐4‐methyl‐2‐phenylthieno[2,3‐ d ]pyrimidine 1 with appropriate hydrazine compounds 2a,b in refluxing ethanol afforded the corresponding 6‐(1‐substituted‐pyrazol‐5‐yl)‐2‐phenylthieno[2,3‐ d ]pyrimidines 3a,b . Cyclization of enaminone derivative 1 with appropriate guanidine compounds 13a‐c in the presence of a basic catalyst yields the corresponding 6‐(2‐substituted‐pyrmidin‐6‐yl)‐2‐phenylthieno[2,3‐ d ]pyrimidines 15a‐c . The compound 15c can be cyclized with appropriate α‐halogenocarbonyl compounds 16a‐d to afford the corresponding 6‐(2‐substituted‐imidazo[1,2‐ a ]pyrimidin‐7‐yl)‐2‐phenylthieno[2,3‐ d ]pyrimidines 17a‐d . On the other hand, the pyrazolo[1,5‐ a ]pyrimidines 20a‐c , pyrido(pyrimido)[2,3:4,3]pyrazolo[1,5‐ a ]pyrimidines 22a‐c , pyrido[4,5:4,3]pyrazolo[1,5‐ a ]pyrimidine 24 , 1,2,4‐triazolo[1,5‐ a ]pyrimidine 26a , and 1,2,3,4‐tetrazolo[1,5‐ a ]pyrimidine derivative 26b were also obtained by the intramolecular cyclization of enaminone derivative 1 with appropriate 5(3)‐amino‐pyrazole derivatives 18a‐c , 21a‐c , 23 , 3‐amino‐1,2,4‐triazole 25a and 5‐amino‐ 1H ‐tetrazole 25b under acid conditions, respectively.