Synthesis and Characterization of Benzo[6,7]Cyclohepta[1,2-b]Pyrazolo[4,3-e]Pyridines

Abstract

In this study, a novel ring system, benzo[6,7]cyclohepta[1,2-b]pyrazolo[4,3-e]pyridin-9-amines was efficiently synthesized. For that, 4-(aryl)-2-thioxo-2,5,6,7-tetrahydro-1H-benzo[6,7]cyclohepta[1,2-b]pyridine-3-carbonitriles were chosen as valuable intermediates. These synthons were reacted with the respective hydrazonyl chlorides in ethanol in the presence of triethylamine. The reaction was stirred at 50°C for 1–1.5 to afford a novel series of 2-oxo-N-phenylpropanehydrazonothioates in 82%–89% yields. Heating of the previous hydrazonothioates in an ethanolic sodium ethanolate solution under reflux for 2–3 h yielded a novel series of 8,11-diphenyl-5,6,7,11-tetrahydrobenzo[6,7]cyclohepta[1,2-b]pyrazolo[4,3-e]pyridin-9-amines in 77%–86% yields. The structures of the novel products were elucidated by elemental-analyses and spectral data.