Synthesis of Some New 6,8‐Disubstituted 7,8‐Dihydropyrimido[2,3:4,3]pyrazolo[1,5‐a]pyrimidines and 6,7,8‐Trisubstituted Pyrimido[2,3:4,3]Pyrazolo[1,5‐a]Pyrimidine Derivatives |
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Authors: | Yuh‐Wen Ho Chia‐Tseng Yao |
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Abstract: | Cyclization of 5‐cyano‐1,6‐dihydro‐4‐methyl‐2‐phenyl‐6‐thioxopyrimidine 4 with excess of 85% hydrazine hydrate afforded the 3‐amino‐4‐methyl‐6‐phenylpyrazolo[3,4‐d]pyrimidine 5 , which can react with appropriate Mannich base derivatives 13a‐c and chalcones 27a,b to yield the corresponding 6,8‐disubstituted 7,8‐dihydropyrimido[2,3:4,3]pyrazolo[1,5‐a]pyrimidines 15a‐c and 30a,b , respectively. On the other hand, the 6,7,8‐trisubstituted pyrimido[2,3:4,3]pyrazolo[1,5‐a]pyrimidine derivatives 8a‐g, 20a‐e, 36 and 38 were obtained by treatment of compound 5 with appropriate 1,3‐diketones 6a‐g , 3‐dimethylamino‐1‐(substituted)prop‐2‐enones 18a‐e , 3‐aminocrotononitrile 3 , and ethoxymethylenemalononitrile 37 under acidic condition, respectively. |
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Keywords: | 5‐Cyano‐1,6‐dihydro‐4‐methyl‐2‐phenyl‐6‐thioxopyrimidine 3‐Amino‐6‐phenylpyrazolo‐[3,4‐d]pyrimidine 6,8‐Disubstituted 7,8‐dihydropyrimido[2,3:4,3]pyrazolo[1,5‐a]pyrimidines 6,7,8‐Trisubstituted pyrimido[2,3:4,3]pyrazolo[1,5‐a]pyrimidines |
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