Reaction of substituted pyrido[1,2-a]benzimidazoles with electrophilic agents

The reactivity of substituted pyrido[1,2-a]benzimidazoles toward electrophilic aromatic substitution has been studied. An unusual introduction of an electrophilic species at the ortho position with respect to an electron-withdrawing group was found, and investigated. Changing the substituent nature from a meta director to an ortholpara director did not alter the selectivity of electrophilic substitution. Assignment of the proton and carbon spectra for the products of SEAr reactions were carried out using 1D and 2D NMR and the structures of selected nitro- and dinitropyrido[1,2-a]benzimidazoles were confirmed by single crystal X-ray diffraction. (C) 2015 Elsevier Ltd. All rights reserved.