Neighboring effect by heteroaromatic rings: Formation of skeletally rearranged adducts by cycloaddition reaction of norbornadiene-fused pyridazines and pyrazines with 4-phenyl- 1,2,4-triazole-3,5(4H)-dione

Article abstract of DOI:10.1016/S0040-4020(99)00821-2

Norbomadiene-fused pyridazines and pyrazines reacted with 4- phenyl-1,2,4-triazole-3,5(4H)-dione to give skeletally rearranged adducts in moderate yields. A similar reaction with fused pyridazine N-oxides or a fused pyrazine N-oxide resulted in the regioselective formation of the rearranged adduct. The formations of the skeletally rearranged adducts would be ascribed to the intervention of bridged heteroarenium ion intermediates formed by the neighboring group participation of heteroaromatic rings.