A highly practical and convenient halogenation of fused heterocyclic N-oxides

摘要

A novel, simple and practical method for the regioselective halogenation of fused heterocyclic N-oxides has been developed. It employs Vilsmeier reagent, generated in situ by PDX3 and DMF, as both the activating agent and the nucleophilic halide source. The method is amenable across a broad range of substrates, including quinolines, isoquinolines and the diazine N-oxides, possessing a variety of substitution patterns. Furthermore, all of the reagents associated are cheap and easy to obtain. The potential extension of this method to a one-pot oxidation/halogenation sequence that obviates the need for isolation of the N-oxide intermediates is also presented. (C) 2016 Elsevier Ltd. All rights reserved.