Polyfluoroheterocyclic compounds. Part XXIV. Thermal elimination of molecular nitrogen from polyfluoro- and polychloro-pyridazines

Abstract

Perfluorotetraphenylpyridazine and perfluorodialkyldiarylpyridazines have been synthesised by reaction of pentafluorophenyl-lithium or tetrafluoro-4-pyridyl-lithium with tetrafluoropyridazine or perfluoro-4,5-dialkylpyridazines. Pyrolytic elimination of nitrogen from these pyridazines is described, giving the acetylenes C₆F₅·CCR_F[R_F= C₆F₅, C₂F₅, or (CF₃)₂CF] and (4-C₅F₄N)CCCF(CF₃)₂. Pyrolysis of tetrachloropyridazine leads to a mixture of products arising from nitrogen elimination. Similarly perchlorocinnoline yields perchlorophenylacetylene, and perchlorophthalazine gives tetrachlorophthalonitrile. These results suggest that nitrogen extrusion from pyridazines leads to diradical intermediates rather than cyclobutadienes or tetrahedral species.