Thoai Nguyen

Transformation de l'hexafluoropropène en alcool trifluoroallylique, précurseur des α-fluoroacrylates

Abstract The α-fluoroacryloyl fluoride precursor of α-fluoroacrylic acid esters can arise from an allylic transposition of trifluoroallylic alcohol of which two methods of preparation are presented. In the first, dehydrofluoration of the alcohol CF 3 CFHCH 2 OH ( 4 ) is used. This alcohol is generated from the ester CF 3 CFHCOOC 2 H 5 ( 3 ). In the second, dehalogenation of the alcohol CF 3 CFBrCH 2 OH ( 10 ) by zinc is used. The latter is formed by the selective reduction of the ester CF 3 CFBrCOOC 2 H 5 ( 9 ).

Perfluorothioalkanoyl halides. Preparation from sulfides

Abstract Perfluorothioalkanoyl halides were generated from alkyl perfluoroalkyl sulfides by reaction with TiF 4 , TiCl 4 or ClS0 3 H. The alkyl groups were benzyl or methyl, the former was more suitable. An α-bromoperfluoroalkyl-sulfide gave a perfluorothioalkanoyl halide more easily than the corresponding α-chloro sulfide which gave the thioalkanoyl chloride. An exchange between the α-halogen atom X of the sulfide R F CFXSR H (X=Cl, Br) and the halogen atom of the Lewis acid can occur.

Transformation d'oxydes d'alkyles et de polyfluoroalkyles par les acides de Lewis. Influence des radicaux alkyles.

Abstract The generation of perfluoroalkanoyl fluorides from perfluoroalkyl ethers by Lewis acids R H OCF 2 R F → FR H + R F COF depends mainly upon the nature of the alkyl R H radical. It is necessary to use R H groups with donor character and also electrophilic groups present on the radicals can facilitate the breaking of the R H -O bond. As examples, ethers with Me 3 SiCH 2 CH 2 or CH 2 =CH-CH 2 groups allowed reactions to occur readily at room temperature or below using common Lewis acids such as ZnCl 2 , BF 3 -Et 2 O, AlCl 3 .

Access to 2-fluoroacrylates and their 3-chloro derivatives by chemical hydrogenolysis of 3,3-dichloro-2-fluoroacrylates

Abstract The formation of 3-chloro-2-fluoroacrylates 2 and 2-fluoroacrylates 3 by hydrogenolysis of 3,3-dichloro-2-fluoroacrylates 1 was studied by using Bu 3 SnH, zinc, the sodium sulphite/sodium formate mixture or iron pentacarbonyl in the presence of a hydrogen donor (Et 3 SiH or CH 3 OH). The two last couples can be used to prepare the 3-chloro derivatives 2 , whereas for the preparation of the 3,3-dihydro derivatives 3 , zinc is the most appropriate reducing agent. Keywords: 2-Fluoroacrylate; 3-Chloro-2-fluoroacrylate; 3,3-Dichloro-2-fluoroacrylate; Tributyltin hydride; Zinc; Sodium sulphite; Sodium formate; Iron pentacarbonyl; NMR spectroscopy; IR spectroscopy

Condensation du chloroforme avec des oléfines fluorées en milieu basique

The condensation of CHCl3 with CF3CFCF2 under phase-transfer catalysis leads mainly to CF3CFHCFCCl2 (1a). In the case of CF2CFCl, a cyclopropane adduct 3b is obtained along with CHClFCFCCl2 (1b). The yields of adducts 1a,b or 3b are ca. 30%. As the working conditions are simple and the starting materials are readily available, the method could provide an interesting route to some perhalogeno-cyclopropanes and to short-chain hydro-halogeno alkenes.

Synthesis of 3,3-dichloro-2-fluoroacrylic esters by thermal opening of alcoxy perhalogeno cyclopropanes

Abstract Alcoxyperhalogenocyclopropanes I are easily prepared by dichlorocarbene addition to the halogenated enol ether derived from chlorotrifluoroethylene, under PTC conditions. Thermal opening of the cyclopropane ring leads to the formation of 3,3-dichloro -2-fluoroacrylic ester II by chlorine atom departure from the CFCl group in preference to the one from the CCl 2 group. This selectivity could be due to the slowing down of the substitution by the other geminal chlorine atom in the latter case.

A short synthesis of α-fluoro acrylic derivatives

Abstract Primary polyfluoroallylic alcohols CFXCF-CH 2 OH 2 (XF, Cl) were obtained by action of an alkyl lithium at 0° on 3-Hydropolyfluoro propanols HCFX-CF 2 -CH 2 OH 1 In acidic medium allylic alcohols 2 rearranged into 2-Fluoro acryloyl fluoride CH 2 CFCOF 3 . The whole procedure constitutes a two steps process of obtaining 3 . By extension of the method to alcohols R-CF-CH 2 OH 4 , which were obtained by action of alkyl lithium at 20°C on alcohols 1 , 1-Fluorovinyl ketones CH 2 CF-CO-R 5 were prepared: