Polyfluorocycloalkenes. Part XIX. Some reactions and compounds from 1,2-bis(trifluoromethyl)octafluorocyclohexene

Convenient synthesis of fluorinated alkanes and cycloalkanes by hydrogenation of perfluoroalkylalkenes under ultrasound irradiation

“…It should be noted that we observed a total lack of reactivity with the cyclohexene substrates using the same conditions ( Table 2, entry 2). These last three fluorinated alkenes are less hindered showing the sensitivity of this catalyst to steric interactions and explaining the previous literature results [18,19].…”

“…The addition of an excess of thionyl chloride to the mixture of alcohol and pyridine in the presence of a catalytic amount of 4-dimethylaminopyridine gave the corresponding alkene derivatives 4. The dehydration proceeds first with the formation of an intermediate chlorosulfite, which can be observed by 19 F NMR of the reaction mixture. The chloride can subsequently act as a base to promote the b-elimination process but the reaction is very slow and gives mainly to degradation products.…”

“…Whilst the chemistry of perfluorinated alkenes is well established, alkenes with both alkyl and trifluoromethyl, or pentafluoroethyl substituents, are less common and only a few examples concerning their reactivity with hydrogen have been published [19,20]. In these reports, the reactions were performed under high pressure (100 bar) with palladium on charcoal as catalyst and during a long time, until the conversion of the alkenes was complete.…”

“…The experiments were performed in a commercially available laboratory bath system ultrasonic generator. The reactions were followed by 19 F NMR observing the disappearance of the vinyl trifluoromethyl signal around À70 ppm with the concomitant formation and growth of the fluoroalkane compound's signals (Scheme 4, Table 2). …”

“…19 F NMR spectra were taken on a Bruker AC300 (282 MHz) or AC200 (188 MHz) spectrometer using CFCl 3 as external standard. 13 C NMR were recorded on a Bruker AC300 (75 MHz) or AC200 (50 MHz) spectrometer.…”