Inverse electron-demand Diels-Alder reaction of 3 6-disubstituted 1 2 4 5-tetrazines with tributylstannylacetylenes containing a substituent gave 4-(tributylstannyl)pyridazines. Particularly  dimethyl 1 2 4 5-tetrazine-3 6-dicarboxylate gave 4-(tributylstannyl)pyridazines in good yields. Substitution reaction of 3 6-diphenyl-4-(tributylstannyl)pyridazine was also described.