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.
A Solvent-Free Protocol for the Green Synthesis of 5-Arylidene-2,4-thiazolidinediones Using Ethylenediamine Diacetate as Catalyst