Microwave-Assisted Copper Powder-Catalyzed Synthesis of Azole-Fused Pyrimidinones

Background: Azole-fused pyrimidinones have been synthesized and tested for biological activities. The present copper-catalyzed version will be attempted as an alternative synthetic method for such N-fused hybrid structures. Objective: This research aims to develop a new synthetic method of azole-fused pyrimidinones from β-bromo-α,β-unsaturated amides and azoles (benzimidazole, imidazole and pyrazole). Method: β-Bromo-α,β-unsaturated amides react with azoles in DMF at 100°C for 1 h in the presence of a catalytic amount of copper powder and base under microwave irradiation. Result: β-Bromo-α,β-unsaturated amides are coupled and cyclized with azoles to give the corresponding azolefused pyrimidinones in moderate to good yields via tandem intermolecular C-N coupling and C-N formative cyclization by C-H activation. Conclusion: This work provides a new method for synthesizing N-fused hybrid scaffolds such as benzimidazo[ 1,2-a]pyrimidin-2-ones, imidazo[1,2-a]pyrimidinones and pyrazolo[1,5-a]pyrimidinones from readily available starting compounds.