Copper-Catalyzed Intermolecular Oxidative Cyclization of Halo- alkynes: Synthesis of 2-Halo-substituted Imidazo[1,2-<i>a</i>]pyridines, Imidazo[1,2-<i>a</i>]pyrazines and Imidazo[1,2-<i>a</i>]pyrimidines
AbstractAn efficient copper‐catalyzed method for the synthesis of 2‐haloimidazopyridines with aminopyridines and haloalkynes using molecular oxygen as oxidant in a one‐pot manner has been developed. In this process, the reaction appears to be very general and suitable for the construction of a variety of 2‐halo‐substituted imidazopyridines, imidazopyrazines and imidazopyrimidines. The intermolecular oxidative diamination of haloalkynes was achieved for the first time. Importantly, the mild reaction conditions and the efficient conversion of the alkyl‐substituted haloalkynes are great improvements over the existing methods. Moreover, the resultant 2‐haloimidazo[1,2‐a]pyridines could be efficiently converted to other functionalized imidazopyridine products via substitution, coupling reactions and other transformations, which further indicates potential applications of this method in synthetic and pharmaceutical chemistry.magnified image