Heterocyclic polyfluoro-compounds. Part XIII. Thermal reactions of perfluoro(tetrahydro-2-methyl-2H-1,2-oxazine) and perfluoro-(3,6-dihydro-2-methyl-2H-1,2-oxazine) : synthesis and properties of perfluoro-(1-methyl-2-pyrrolidone), perfluoro-(1-methyl-2-oxo-3-pyrroline), and perfluoro-(1-methylazetidine)
Perfluoro(tetrahydro-2-methyl-2H-1,2-oxazine), prepared by treatment of perfluoro-(3,6-dihydro-2-methyl-2H-1,2-oxazine) with cobalt trifluoride, decomposes at 480–580° in platinum to give, inter alia, perfluoro-(1-methylazetidine) and perfluoro-(1-methyl-2-pyrrolidone); when the tetrahydro-oxazine is passed over iron at 350° perfluoro-(1-methyl-2-pyrrolidone) is the major product. Similarly, treatment of perfluoro-(3,6-dihydro-2-methyl-2H-1,2-oxazine) with iron at 400° causes it to undergo defluorinative ring-contraction to perfluoro-(1-methyl-2-oxo-3-pyrroline). Perfluoro-(1-methyl-2-pyrrolidone) reacts with sulphur tetrafluoride to give perfluoro-(1-methylpyrrolidine), and is degraded to tetrafluorosuccinic acid by aqueous base; photolysis or pyrolysis of the pyrrolidone gives perfluoro-(1-methylazetidine), perfluoro(methylenemethylamine) and tetra-fluoroethylene. Chlorination of perfluoro-(1-methyl-2-oxo-3-pyrroline) provides perfluoro-(trans-3,4-dichloro-1-methyl-2-pyrrolidone), which reacts with aqueous base to give αβ-dichlorodifluorosuccinic acid. Perfluoro-(1-methylazetidine) decomposes at temperatures above 740° into an equimolar mixture of perfluoro(methylene-methylamine) and tetrafluoroethylene.