Solvent-dependence of KI Mediated Electrosynthesis of Imidazo[1,2-a]pyridines

Abstract

Iodized salts are widely used as mediators to promote C-H functionalization. Solvents and additives have been described as significant roles in these reactions. However, the further electrochemical investigations have rarely been reported. Herein, a KI mediated electrochemical annulation between acetophenones and 2-amniopyridines was developed. We revealed the effect of acids and solvents by cyclic voltammetry(CV), differential pulse voltammetry(DPV), and square wave voltammetry(SWV). The oxidation of 2-aminopyridine is inhibited at the potential window with the addition of strong acids, and the lowest oxidation potential difference of KI was obtained by utilizing EtOH as solvent. The experimental studies also show that the mixture solvent of EtOH/DMSO(9/1, volume ratio) facilitates the electrochemical cyclization due to the solubility improvement of KI. CF₃SO₃H has been screened as the optimal acid. A range of Imidazo[1,2-a]-pyridines have been synthesized in yields of 42% to 96%. Electrochemical investigations present that the KI mediated electrochemical reaction is probably solvent-dependence.

Keywords

Electrochemical annulation / Electrochemical behavior / Solvent / Strong acid / KI

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