Heterocyclic polyfluoro-compounds. Part XIV. Catalytic hydrogenation of perfluoro-(3,6-dihydro-2-methyl-2H-1,2-oxazine) and of perfluorocyclopentene

Abstract

Vapour-phase hydrogenation of perfluoro-(3,6-dihydro-2-methyl-2H-1,2-oxazine) in the presence of 1% palladium–alumina gave 4H,5H/-hexafluorotetrahydro-2-trifluoromethyl-1,2-oxazine and small amounts of 4H,4H,5H- and 4H,5H,5H-pentafluorotetrahydro-2-trifluoromethyl-1,2-oxazine. Dehydrofluorination of the 4H,5H-compound with aqueous potassium hydroxide gave an equimolar mixture of 4H- and 5H-pentafluoro-3,6-dihydro-2-trifluoromethyl-2H-1,2-oxazine. Hydrogenation of perfluorocyclopentene in the presence of 1% palladium–alumina gave 1H,2H/-octafluorocyclopentane and 1H,1H,2H-heptafluorocyclopentane. The ¹⁹F and ¹H n.m.r. spectra of these hydrofluoro-compounds are discussed.