Synthesis of new hybrid compounds of imidazo[1,2-a]pyrimidine/pyridine based on quinoxaline through palladium-catalyzed coupling reactions and heteroannulation

Abstract

New hybrid compounds, including imidazo[1,2-a]pyrimidin-2-yl(3-(substituted)quinoxalin-2-yl)methanone and its imidazo[1,2-a]pyridine analogs, have been successfully prepared via palladium-catalyzed reactions. The synthesis involved the reaction of 3-substituted-2-chloroquinoxalines with 2-amino-1-(prop-2-yn-1-yl)pyrimidinium/pyridinium bromide under optimized reaction conditions. These conditions included Pd(PPh₃)₂Cl₂ (5 mol %), CuI (10 mol%) in the presence of Et₃N in DMF at 70 °C, resulting in the formation of the desired hybrid compounds. Furthermore, imidazo[1,2-a]pyridine hybrid compounds were synthesized through one-pot multicomponent reactions of 2,3-dicholoroquinoxaline, 2-amino-1-(prop-2-yn-1-yl)pyridinium bromide, primary and secondary amines, under optimized conditions. These processes provided efficient protocols to synthesize novel imidazo[1,2-a]pyrimidine/pyridine based on quinoxaline through palladium-catalyzed reaction with high yields. A one-pot reaction, high reaction yields, energy efficiency, and a straightforward reaction process are significant advantages of this protocol.