Heterocyclic polyfluoro-compounds. Part 26. Synthesis of 3,6-bis-trifluoromethyl-pyridazines and -dihydropyridazines

Abstract

Bistrifluoromethyl-s-tetrazine reacts with styrene to yield 4-phenyl-3,6-bistrifluoromethyl-1,4-dihydropyridazine, with cyclohexene to give 3,8-bistrifluoromethyl-1,3a,4,5,6,7-hexahydrophthalazine, with 2,3-dimethylbut-2-ene to yield 4,4,5,5-tetramethyl-3,6-bistrifluoromethyl-4,5-dihydropyridazine and with norbornadiene to give, it is tentatively proposed, 2,5-bistrifluoromethyl-3,4-diazabicyclo[4.3.0]nona-1,4,8-triene, plus 3,6-bistrifluoromethyl-pyridazine. The last compound is formed by reaction of the tetrazine with acetylene, and 4-methyl- and 4,5-bistrimethylstannyl-3,6-bistrifluoromethyl-pyridazines are formed by reaction with propyne and with bistrimethylstannylacetylene, respectively.

Reaction of the tin compound with iodine and with chlorine yields 4,5-di-iodo- and -dichloro-3,6-bistrifluoro-methylpyridazine, respectively, and the latter compound yields perfluoro-3,6-dimethylpyridazine with potassium fluoride.

Perfluoro-3,6-dimethylpyridazine rearranges photochemically in the vapour phase into perfluoro-2,5-dimethylpyrazine.