Synthesis of 1,4,5,6-tetrahydropyrazolo[3,4-d]pyrido[3,2-b]azepine

Article abstract of DOI:10.1002/jhet.5570370107

The synthesis of 7,8-dihydro-5(6H)-quinolinone (3) from commercially available 3-amino-2-cyclohexen-1-one (1) and 3-(dimethylamino)acrolein (4) in 23% yield avoids the preparation of propynal (2). Conversion of 5-(4- methylphenylsulfonyl)-6,7,8,9-tetrahydro-5H-pyrido[3,2-b]azepine (12) to 6- (4-methylphenylsulfonyl)-1,4,5,6-tetrahydropyrazolo[3,4-d]pyrido[3,2- b]azepine (24) is described. Removal of the N-(4-methylphenylsulfonyl) group with 40% sulfuric acid in acetic acid gave the tricyclic azepine 26. Application of a similar series of reactions to 5-(4-nitrobenzoyl)-6,7,8,9- tetrahydro-5H-pyrido[3,2-b]azepine (13) afforded 6-(4-nitrobenzoyl)-1,4,5,6- tetrahydropyrazolo[3,4-d]pyrido[3,2-b]azepine (25).