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The thermal isomerization reaction of ortho-vinyl tert-anilines and their heterocyclic analogues via tert-amino effect affords tetrahydropyrido-fused heterocyclic ring systems with a new C-C bond formation between the vinyl and tert-amino groups. A novel series of 5-amino-4-vinyl-3(2H)-pyridazinone derivatives were prepared to study the role of substituents of the pyridazinone ring and the vinyl group in their isomerization reaction to tetrahydropyrido [2,3-d]pyridazines. In particular, 6-phenyl and 5-trioxopyrimidinediylmethylene substituents were found to significantly increase the rate of isomerization. Compounds possessing benzyl and methyl groups as amino substituents isomerized with the involvement of the benzyl group. On the basis of experiments with deuterated compounds, an intramolecular pathway was confirmed for the isomerization.

Pyridazine derivatives R 0500Pd-Catalyzed Intramolecular Direct Arylations at High Temperature. -The microwave-assisted Pd-catalyzed high-temperature intramolecular arylation reaction proceeds smoothly at aromatic C-Br and activated azahetaromatic C-Cl bonds to afford a diversity of fused pyridazine or pyridine derivatives in good yields. Main features of the reaction are low catalyst loading (1mol% in most cases), short reaction times (10 -30 minutes) and wide applicability. -(FRANCK, P.; HOSTYN, S.; DAJKA-HALASZ, B.; POLONKA-BALINT, A.; MONSIEURS, K.; MATYUS, P.; MAES*, B. U. W.; Tetrahedron 64 (2008) 26, 6030-6037; Dep. Chem., Univ. Antwerp, B-2020 Antwerpen, Belg.; Eng.) -Mischke 42-144