Zwitterionic C–N Bond Cleavage by the Accumulation of Charge: Green Synthesis of Amino Thiazolyl Benzimidazolium Bromide and Benzimidazol‐Thiazole under Microwave Irradiations

The Zwitterionic curious methodology for the regioselective C–N bond cleavage to synthesize the anticancer substituted amino thiazolyl benzimidazolium bromide and its thiazole. The cyclic hydrogen bonding (multiple hydrogen bonding) approach with accumulation of charge have been applied for the regioselective C–N bond cleavage by organocatalysis. It is metal free one‐pot reaction fascinated by microwave irradiations. The zwitterionic L‐proline have been proposed as catalyst and acceptor partner in donor–acceptor cyclic hydrogen bonding system. The work is green and sustainable without separation, purification and solvent extraction. The respective accumulation of positive charge and negative charge at lowest occupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) decreases energy gap in cyclic hydrogen bonding. The accumulation of positive charge on two carbons executed the C–N bond cleavage effectively by the migration of benzimidazole moiety. The density functional theory is used to study the intermediates using HOMO‐LUMO frontier orbital concept. This elite cyclic hydrogen bonding between bromide salt and neutral thiazole moiety abetted the solidification of product in solution. The synthesized products are anticancer agents. All products created new library of amino thiazolyl benzimidazolium bromide and their thiazole heterocycles.