1998 Volume 71 Issue 6 Pages 1443-1449
A norbornadiene-fused pyrazine was prepared by the condensation reaction of bicyclo[2.2.1]hept-5-ene-2,3-dione with ethylenediamine followed by oxidation. Treatments of the norbornadiene-fused pyrazine and its benzo derivative with bromine in carbon tetrachloride or in dioxane afforded trans-adducts as major products, accompanied by the formations of cis-adducts and dibromo derivatives derived from Wagner–Meerwein type skeletal rearrangement, while bromination of a fused dicyanopyrazine in carbon tetrachloride gave only a trans-adduct. In contrast, a fused pyrazine with an electron-donating N-oxide group gave a 7,9-dibromo derivative as the main component. The possibility of the intervention of a 2H-pyrazinium ion for the formation of the skeletally rearranged products is discussed together with the results of ab-initio (3-21G*) calculations.
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