Friedel-Crafts chemistry. Part 45: expedient new improved process for the synthesis of oxacarbazepine precursor 10,11-dihydro-10-oxo-5H-dibenz[b,f]azepine via Friedel-Crafts cycliacylations

Abstract

An unprecedented efficient methodology for the synthesis of 10,11-dihydro-10-oxo-5H-dibenz[b,f]azepine via a three new synthetic pathways is described. The key steps of this approach are based on classical Friedel-Craft ring closures of three precursors 1-(2-(N-phenyl-Ntosylamino)phenyl)-2-bromoethanone, ethyl 2-(2-(N-phenyl-N-tosylamino)phenyl)acetate or 2-(2-(N-phenyl-N-tosylamino)phenyl)acetic acid, by using AlCl 3 /CH 3 NO 2 or AlCl 3 in dichloromethane. For the latter two precursors, P 2 O 5 in toluene worked also well. The precursors were easily obtained in a two-or three -step reaction sequence. Overall, the described approach allows easy and efficient access to the tricyclic dibenzoazepinone ring system from easily accessible starting materials.