The Diels–Alder reaction of 5, 5′-bi-1, 2, 4-triazines with cyclic enamines in the absence of a solvent leads to a range of symmetrical, annulated 2, 2′-bipyridines in good yield. When the reaction is carried out in boiling dioxane only 5-(heteroaryl) 1, 2, 4-triazines are formed. The latter, bearing methylsulfanyl substituents, are oxidized with potassium permanganate to the corresponding methylsulfonyl derivatives, which easily undergo Diels–Alder ...
