Synthesis of Cyclic Ethers with Fluorinated Side Chains

Abstract

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)OCF2CF 2SO2F) gives either bidirectional addition products [CH2CH2CH2OCH(CF2CH3) (1), CH2CH2CH2OCH(CH2CHF2) (2), CH2CH2CH2OCH(CF2CH2F) (3), and CH2CH2CH2OCH(CFHCHF2) (4)] or unidirectional products [CH2CH2CH2OCH(CH2CH 2CF3) (5), CH2-CH2CH2OCH(CF2CHFCF3) (6), CH2CH2CH2OCH(CF2CHFC 5F11) (7), and CH2CH2CH2OCH(CF2CHFOCF 2CF-(CF3)OCF2CF2SO2F) (8)] depending on the structure of the alkene. Reaction of dioxane with CF2=CFOCF2-CF(CF3)OCF2CF 2SO2F gives a single product, CH2OCH2CH2OCH(CF2CHFOCF 2CF(CF3)OCF2CF2SO2F) (9). In the case of hexafluoropropene or perfluoroallylbenzene, reaction with an excess of tetrahydrofuran gives only the monosubstituted products CH2CH2CH2OCH(CF2CHFCF2) (6) and CH2CH2CH2OCH(CF2CFHCF 2C6F5) (11) respectively. When tetrahydrofuran is reacted with a 3:1 molar excess of the same two perfluoroalkenes, the disubstituted products CH2CH2CH(CF2CHFCF3)OCH(CF 2CHFCF3) (10) and CH2CH2CH(CF2CFHCF2C 6F5)OCH(CF2-CFHCF2C 6F5) (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)OCF 2CF2SO2F (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)trirnethylsilane reacts with 11 in the presence of a catalytic amount of cesium fluoride to give compound 19, CH2CH2CH2OCH(CF2-CFHCF 2C6F4OC6F5). Two molecules of 11 are bridged by reaction with Me3SiOCH2CF2CF2CF2CH 2OSiMe3 to give CH2CH2CH2OCHCF2CFHCF2C 6F4OCH2CF2CF2CF 2CH2OC6F4CF2CHFCF 2CHOCH2CHCH2 (20), while 12 forms the macroheterocycle OCHCH2CH2CHCF2CFHCF2C 6F4OCH2CF2CF2CF 2CH2OC6F4CF2CFHCF 2 (21) under similar reaction conditions. The lanthanum inflate 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(OSO2CP3)3(18-crown-6-CF2CFHCF 2C6F5)(H2O) (24) and [La(OCH2CH2)5OCH2CHCF 2CFHOCF2C(CF3)FOCF2CF 2SO2F]3+[CF3SO3-]3 (25) respectively. The acid salt La[N(SO2CF3)2]3 (26) was also prepared and characterized, and reacted with dibenzo-18-crown-6 to give the complex dibenzo-18-crown-6-La[N(SO2CF3)2]3 (27).