Reactions involving fluoride ion. Part IX. Syntheses involving octafluoroisobutene

Octafluoroisobutene reacts with pentafluoropyridine in the presence of fluoride ion, at 80°, to give perfluoro-2,4,6-tri-t-butylpyridine whereas, at 20°, perfluoro-4-t-butylpyridine is formed. Reaction of Octafluoroisobutene with tetrafluoropyridazine, at 80°, gives perfluoro-3,6-di-t-butylpyridazine exclusively, although at lower temperatures perfluoro-4-t-butyl or-3,5-t-butyl derivatives are obtained. The variation in the orientation of products formed with the olefin used in polyfluoroalkylations with tetrafluoropyridazine is discussed. Perfluoro-t-butylpyridines show no indication of restricted rotation even at low temperatures and this illustrates how increased crowding can lower a rotational barrier.