Regioselective palladium-catalyzed amination of 2-chloro-3-iodopyridine followed by a subsequent palladium-catalyzed amination leads to 2,3-diaminopyridines. Treatment with triphosgene affords highly functionalized unsymmetrical imidazo[4,5-b]pyridin-2-ones in just three synthetic steps. A two-step synthesis of pseudosymmetrically disubstituted imidazo[4,5-b]pyridin-2-ones, 1,4-disubstituted pyrido[2,3-b]pyrazinediones, and 1,3-disubstituted thiadiazolo[3,4-b]pyridin-2-ones is also described.