6-Bromo-1-(1,2-propadienyl)-3-(2-propynyl)-1H-imidazo[4,5-b]pyridin-2(3H)-one

The reaction of propargyl bromide and 6-bromo-1,3-dihydroimidazo[4,5-b]pyridin-2-one in refluxing dimethylformamide yields the title compound, C12H8BrN3O, which features nitrogen-bound propadienyl and propynyl substituents. The imidazolopyridine fused ring is planar (r.m.s. deviation = 0.012 Å); the propadienyl chain is coplanar with the fused ring as it is conjugated with it, whereas the propynyl chain is not as the nitrogen-bound C atom is a methylene linkage. The acetylenic H atom is hydrogen bonded to the carbonyl O atom of an adjacent molecule, forming a helical chain runnning along the b axis.