An Electrolyte-and Catalyst-Free Electrooxidative C-3 Sulfonylation Of Imidazo[1,2-a]pyridines

The direct electrochemical oxidation has been widely applied in organic synthesis due to the simple and mild reaction conditions,high selectivity,few by-products,high product purity and high productivity.Up to now,the efficient synthetic methods of 3-sulfonylated imidazo[1,2-a]pyridines were the C-H activation of imidazo[1,2-a]pyridines with the photosensitizer or transition-metal-catalyst at high reaction temperature.Herein,a green and efficient electrochemical oxidation method was developed for the synthesis of 3-sulfonyl imidazo[1,2-a]pyridine.The main research contents are as follows:1.We have developed a direct electrochemical oxidation method to synthesize a series of 3-sulfonyl imidazo[1,2-a]pyridines by using 2-arylimidazo[1,2-a]pyridines and sodium sulfonates as substrates.This catalytic system showed the excellent functional group tolerance and substrate suitability without electrolytes and catalysts(Scheme 1).#12 Scheme 12.The reaction mechanism has been studied by control experiments and density functional theory(DFT)calculations.The results showed that the reaction might be occurred via a radical process.