Synthesis of pryridine and 2,2'-biprydine derivatives from the aza Diels-Alder reaction of substituted 1,2,4-triazines

Amidrazone 1a and the tricarbonyl derivatives 2b–d reacted in boiling ethanol in the presence of 2,5-norbornadiene 5 giving the pyridine derivatives 6b–d respectively (59–72%) and in the presence of 2,3-dihydrofuran 7 yielding the lactones 10b–d (39–44%). The 2,2′-bipyridine derivatives 6e–g were similarly obtained in good yield (81–87%) from the reaction of amidrazone 1b and tricarbonyl derivatives 2b–d in the presence of 2,5-norbornadiene 5.