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.