Cyclization of sulfoxonium ylides with 2-aminopyridines towards imidazo[1,2-a]pyridines

Abstract

A method for cyclization of 2-aminopyridines and sulfoxonium ylides is developed. The approach would avoid the requirement of pre-functionalized, Ortoleva-King typed alpha-haloketones for such cyclization. The annulation was facilitated in the presence of nickel(II) bromide, presumably as the Lewis acid catalyst. An array of functionalities including secondary amine, nitro, and halogen groups were tolerated. Two examples of alkyl sulfoxonium ylides were also presented. Our method feature a new approach to afford synthetically useful C2-substituted imidazo[1,2-a]pyridines from derivatives of benzoic acids.