Polyfluoroalkylated 1,3-thiazolines: synthesis from polyfluoro-2,3-epoxyalkanes

The interaction of polyfluoro-2,3-epoxyalkanes with thiourea and thiosemicarbazide results in 2-amino-5-fluoro-4-hydroxy-4,5-di(polyfluoroalkyl)-1,3-thiazolines and 5-fluoro-2-hydrazino-4-hydroxy-4,5-di(polyfluoroalkyl)-1,3-thiazolines, respectively. Asymmetric oxiranes yield mixtures of regioisomers, and the ring opening has been found to occur mainly near the bulkier fluoroalkyl group. The reaction with thiourea proceeds stereospecifically in dimethyl sulfoxide. The molecular structure of E-isomers of 2-amino-5-fluoro-4-hydroxy-4,5-bis(trifluoromethyl)-1,3-thiazoline and 2-amino-5-fluoro-5-heptafluoropropyl-4-hydroxy-4-trifluoromethyl-1,3-thiazoline has been established by X-ray crystallography.