Synthesis of Cyclic Ethers with Fluorinated Side Chains

Di-tert-butyl peroxide initiated free radical addition of THF to various fluorinated alkenes (CF2CH2, CF2CFH, CH2CHCF3, CF2CFCF3, CF2CFC5F11, CF2CFOCF2CF(CF3)OCF2CF2SO2F) gives either bidirectional addition products [CH2CH2CH2OCH(CF2CH3) (1), CH2CH2CH2OCH(CH2CHF2) (2), CH2CH2CH2OCH(CF2CH2F) (3), and CH2CH2CH2OCH(CFHCHF2) (4)] or unidirectional products [CH2CH2CH2OCH(CH2CH2CF3) (5), CH2CH2CH2OCH(CF2CHFCF3) (6), CH2CH2CH2OCH(CF2CHFC5F11) (7), and CH2CH2CH2OCH(CF2CHFOCF2CF(CF3)OCF2CF2SO2F) (8)] depending on the structure of the alkene. Reaction of dioxane with CF2CFOCF2CF(CF3)OCF2CF2SO2F gives a single product, CH2OCH2CH2OCH(CF2CHFOCF2CF(CF3)OCF2CF2SO2F) (9). In the case of hexafluoropropene or perfluoroallylbenzene, reaction with an excess of tetrahydrofuran gives only the monosubstituted products CH2CH2CH2OCH(CF2CHFCF3) (6) and CH2CH2CH2OCH(CF2CFHCF2C6F5) (11) respectively. When tetrahydrofuran is reacted with a 3:1 molar excess of the same two perfluoroalkenes, the disubstituted products CH2CH2CH(CF2CHFCF3)OCH(CF2CHFCF3) (10) and CH2CH2CH(CF2CFHCF2C6F5)OCH(CF2CFHCF2C6F5) (12) are formed respectively. When 18-crown-6 is reacted in the same way with fluoroalkenes in a 1:1 molar ratio, the monosubstituted products 18-crown-6-CH2CH2CF3 (13), 18-crown-6-CF2CHFCF3 (14), 18-crown-6-CF2CFHCF2C6F5 (15), and 18-crown-6-CF2CHFOCF2CF(CF3)OCF2CF2SO2F (16) are obtained. Polyfluorinated 18-crown-6 products containing three and two polyfluroalkyl/aryl groups are prepared when 18-crown-6 is reacted with a 3:1 molar excess of perfluoropropene and perfluoroallylbenzene to give 18-crown-6-(CF2CHFCF3)3 (17) and 18-crown-6-(CF2CFHCF2C6F5)2 (18), respectively. (Pentafluorophenoxy)trimethylsilane reacts with 11 in the presence of a catalytic amount of cesium fluoride to give compound 19, CH2CH2CH2OCH(CF2CFHCF2C6F4OC6F5). Two molecules of 11 are bridged by reaction with Me3SiOCH2CF2CF2CF2CH2OSiMe3 to give CH2CH2CH2OCHCF2CFHCF2C6F4OCH2CF2CF2CF2CH2OC6F4CF2CHFCF2CHOCH2CH2CH2 (20), while 12 forms the macroheterocycle OCHCH2CH2CHCF2CFHCF2C6F4OCH2CF2CF2CF2CH2OC6F4CF2CFHCF2 (21) under similar reaction conditions. The lanthanum triflate complexes of 18-crown-6 (22) and 18-crown-6(CF2CFHCF3) (23) were prepared and the structures were obtained via single-crystal X-ray analysis. Although crystals suitable for single-crystal X-ray analysis could not be formed, lanthanum triflate complexes were formed with polyfluorinated ethers 15 and 16 to give the fluorinated complexes La(OSO2CF3)3(1