Reaction of 2-(aminomethyl)pyridine with selenium dioxide leads to the formation of imidazo[1,5-a]pyridine (2-azaindolizine) skeleton in a single step. The major products of the reactions are 3-(2-pyridyl)imidazo[1,5-a]pyridine, bis[3-(2-pyridyl)imidazo[1,5-a]pyridin-1-yl] selenide, or the corresponding diselenide depending upon the reaction conditions. The structures of these selenium-bridged imidazo[1,5-a]pyridine derivatives are disclosed by X-ray crystal structural analyses. For the diselenide, the unusual dihedral angle C Se Se C of 56.0 degrees was observed indicating pi-pi intramolecular interaction between the fused six-membered rings.