Control over borrowing hydrogen and acceptorless dehydrogenative coupling process for the Co(iii)–NHC catalysed chemoselective alkylation and cyclisation of 1,2-phenylenediamine with alcohols

Abstract

The one-pot methodology offering either the alkylation or cyclisation of 1,2-phenylenediamine using alcohol exploiting a single catalyst system has remained unexplored. Herein, we report the chemoselective effective alkylation and cyclisation of 1,2-phenylenediamine with alcohol by simply switching the substituent on the supporting NHC ligand of cobalt(III) complexes. This varying catalytic behaviour of the complexes under consideration towards the selective formation of different products was fairly understood by analyzing their electronic properties based on NMR, electrochemical, and DFT studies. Further, the present protocol is compatible with a wide range of structurally diverse substrates offering ample variations of both amines and alcohols, producing four different types of products starting from 1,2-phenylene diamine. Finally, an array of control experiments, including the deuterium labeling and the identification of different intermediates, assisted in establishing the proposed mechanism.