Metal-Free Site-Specific Hydroxyalkylation of Imidazo[1,2-a]pyridines with Alcohols through Radical Reaction

An effective approach to realize the direct hydroxyalkylation of imidazo[1,2-a]pyridines with alcohols promoted by di-tert-butyl peroxide was described without any metal catalyst. It is the first time that the dehydrogenative C(sp(3))-C(sp(2)) coupling of imidazo[1,2-a]pyridines with alcohols occurred regioselectively at the C-5 position of imidazo[1,2-a]pyridines. Multisubstituted imidazopyridine derivatives were smoothly synthesized in moderate to good yields. Through a series of control experiments, a free-radical pathway was proposed to explain the experiment.