No abstract

No 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.