Abstract
A new method for the synthesis of substituted imidazopyridines (2-azaindolizines) starting from carboxylic acid and 2-methylaminopyridine is described. The reaction of the obtained N-2-pyridylmethylamides with Lawesson's reagent generated the target imidazopyridines, along with the corresponding thioamide intermediates. After a simple filtration on alumina, addition of mercury(II) acetate allowed for total conversion of the thio-amides into the imidazopyridines. The reaction conditions, as well as the influence of the substituent in position 3 of the imidazopyridine ring were explored. We also demonstrated that this heterocyclization was racemization free in the presence of a chiral carbon in position alpha to the heterocycle.