N-Chlorination-induced, oxidative ring contraction of 1,4-dimethoxyphthalazines

Abstract

A rarely explored oxidative ring contraction of electron-rich 1,2-diazine is described. Upon treatment with an electrophilic chlorinating reagent (TCICA), 1,4-dimethoxyphthalazines undergo an N-chlorination-induced ring contraction that is accompanied by the loss of one nitrogen atom. The scope of this unusual reactivity was examined with a range of 1,4-dimethoxyphthalazine derivatives. In addition, a mechanism proceeding via a bicyclic species was proposed on the basis of an isolated reaction intermediate and DFT calculations. © 2020 Elsevier Ltd