Synthesis of polyfunctionalized imidazopyridine carbonitrile and pyridopyrimidine carbothioamide derivatives

A one-pot approach for the synthesis of polyfunctionalized imidazopyridine carbonitrile and pyridopyrimidine carbothioamide derivatives, via reaction of 1,1-bis(methylthio)-2-nitroethene, ethylenediamine/1,3-propanediamine, aromatic aldehydes, and 2-cyanothioacetamide in ethanol at reflux is described. This protocol involved Michael reaction, imine-enamine tautomerization, and cyclization sequences. The reaction with ethylenediamine produced thioxoimidazo[1,2- a ]pyridine-6-carbonitrile or tetrahydroimidazo[1,2- a ]pyridine-6-carbonitrile. When 1,3-propanediamine was used instead of ethylenediamine, pyrido[1,2- a ]pyrimidine-7-carbothioamide was obtained. The different diamine, the substituted aryl group of aromatic aldehyde, and stability of the product may be responsible for their different behaviors. The present method offers desirable advantages including easy accessibility of reactants, mild conditions, absence of a catalyst, simple workup, and easy purification procedure. Graphical abstract