Chemodivergent synthesis of n-(pyridin-2-yl)amides and 3-bromoimidazo[1,2-a]pyridines from alpha-bromoketones and 2-aminopyridines

Abstract

N-(Pyridin-2-yl)amides and 3-bromoimidazo[1,2-a]pyridines were synthesized respectively from alpha-bromoketones and 2-aminopyridine under different reaction conditions. N-(Pyridin-2-yl)amides were formed in toluene via C-C bond cleavage promoted by I-2 and TBHP and the reaction conditions were mild and metal-free. Whereas 3-bromoimidazopyridines were obtained in ethyl acetate via one-pot tandem cyclization/bromination when only TBHP was added, the cyclization to form imidazopyridines was promoted by the further bromination, no base was needed, and the versatile 3-bromoimidazopyridines could be further transferred to other skeletons.