Electro-generated ortho-quinoide intermediates: templates for feasible construction of a series of novel imidazo[2,1-b]thiazole derivatives through one-pot five-step domino hetero-annulation process

Abstract

A series of novel polycyclic structures, with an imidazothiazole central core, were successfully synthesized through the anodic oxidation of catechols in the presence of 2-imidazolidine thione, as nucleophiles in aqueous solution. The cyclic voltammetric results indicated that one-pot multi-step sequential reactions occur between the electrochemically derived o-benzoquinones intermediates and nucleophiles affording fused polyheterocyclic compounds. The mechanism of these catalyst-free, tandem reactions are proved as ECECE or ECECCE pathways using potentiostatic and galvanostatic coulometries. In addition, the electrosyntheses of fused imidazo[2,1-b]thiazoles have been successfully performed in ambient conditions in an undivided cell using an environmentally friendly method with high atom economy and current efficiency. The novel fused polyheterocycles were fully characterized by FT-IR, H-1 NMR, C-13 NMR, and HR-MS spectrometric methods.