Reactions involving fluoride ion. Part III. Preparation, rearrangement, and hydrolysis of perfluoroisopropylpyridazines

Abstract

Tetrafluoropyridazine (5) reacts with hexafluoropropene in the presence of fluoride ion, under mild conditions, to give 3,4,6-trifluoro-5-heptafluoroisopropylpyridazine (3) and 3,6-difluoro-4,5-bisheptafluoroisopropylpyridazine (4); under more vigorous conditions, the 4,5-disubstituted derivative (4) suffers migration of a heptafluoroisopropyl group giving the 4,6-disubstituted isomer (1), and the 3,5,6-trisheptafluoroisopropyl derivative (2) is also obtained. Rearrangement of the 4,5-bisheptafluoroisopropylpyridazine (4) with fluoride ion, in the absence of added hexafluoropropene, is attended by disproportionation to the mono- and tri-substituted pyridazines (3) and (2). Hydrolysis of the 4,5-bisheptafluoroisopropylpyridazine (4) in sulphuric acid at 155° gives 3-fluoro-4,5-bisheptafluoroisopropyl-1 H-pyridazin-6-one (8) and bisheptafluoroisopropylmaleic hydrazide (9), while at 210° bisheptafluoroisopropylmaleic anhydride (7) is produced.