Synthesis of New 5-amino-7-(aryl)-1,2,3,7-tetrahydro-8-nitroimidazo[1,2-a]pyridine- 6-carboxamide and 6-amino-2,3,4,8-tetrahydro-9-nitro-8-(aryl)-1H-pyrido[1,2- a]pyrimidine-7-carboxamide Derivatives

Aim and Objectives: Development of simple synthetic routes for widely used organic compounds from readily available reagents is one of the major tasks in organic chemistry. Therefore, new approaches for increasing the molecular diversity of simple starting materials, are needed. Herein, an efficient synthesis of imidazo[1,2-a]pyridine, pyrido[1,2-a]pyrimidine and pyrido[1,2-a][1,3]diazepine derivatives is described. Materials and Methods: A one-pot, multi-component reaction of nitro ketene aminal derived from the addition of various 1,n-diamines to 1,1-bis(methylthio)-2-nitroethene with cyanoacetamide and aromatic aldehydes is described. The reactions are completed within 2-5 h, in ethanol at reflux, in good to high yields (70-93%). The structures of products were deduced from their IR, mass, 1H NMR, and 13C NMR spectra. Results: Optimal reaction conditions for the synthesis of products were obtained, when ethanol was used as the solvent at reflux. This protocol involves Michael reaction, imine–enamine tautomerization, and cyclization sequences. Conclusion: This work represents an efficient synthesis of imidazo[1,2-a]pyridine, pyrido[1,2-a]pyrimidine and pyrido[1,2-a][1,3]diazepine derivatives via a one-pot, multi-component reaction. The advantages of this protocol are mild conditions, easy accessibility of reactants, absence of catalyst, high atom economy, simple work-up and purification process with no chromatographic technique.