An Efficient One Pot Protocol to the Annulation of Face “d” of Benzazepinone Ring with Pyrazole, Isoxazole, and Pyrimidine Nucleus through the Corresponding Oxoketene Dithioacetal Derivative

Abstract EN

A highly facile single step approach to the annulation of face “d” of benzazepinone nucleus with pyrazole, isoxazole, and pyrimidine ring has been described.

The annulation proceeded smoothly on the reaction of oxoketene dithioacetal derivative 3 with (i) NH2–NH2·H2O, (ii) NH2OH·HCl, (iii) acetamidine hydrochloride, (iv) guanidine nitrate, (v) urea, and (vi) thiourea which yielded the pyrazolo, isoxazolo, and pyrimido annulated analogues of benzazepinone 4–9, respectively, in acceptable yields.

The 4-ketene dithioacetal analogue of 7-fluorobenzo[b]azepine-2,5-dione (3) was in turn obtained from the reaction of 7-fluoro-3,4-dihydro-1H-benzo[b]azepine-2,5-dione (2) (with CS2 + CH3I in presence of t-BuOK).

7-Fluoro-3,4-dihydro-1H-benzo[b]azepine-2,5-dione (2) resulted from the acylation of p-fluoroaniline with succinyl chloride followed by cyclocondensation of the later with polyphosphoric acid (PPA).