Reactions of internal perfluoroolefin oxides with urea

Internal perfluoroolefin oxides reacted with urea to give, depending on the solvent nature, two types of new fluorine-substituted nitrogen-containing heterocycles. 1,5-Bis(perfluoroalkyl)tetraazabicyclo3.3.0]octane-3,7-diones were formed in dimethyl sulfoxide, N,N-dimethylacetamide, and acetonitrile, while the reaction in dioxane resulted in the formation of unexpected products, 2-amino-5-fluoro-4,5-bis(perfluoroalkyl)-4,5-dihydrooxazol-4-ols, existing mainly as trans isomers. trans Orientation of perfluoroalkyl substituents in these compounds was determined by analysis of ¹⁹F-¹⁹F spin-spin coupling constants in the ¹⁹F NMR spectra. The molecular structure of trans-2-amino-5-fluoro-4,5-bis(trifluoromethyl)-4,5-dihydrooxazol-4-ol was studied by X-ray analysis.