Fluoro-olefin chemistry. Part 18. Thermal reaction of hexafluoropropene with diphenylmethane, butylbenzenes, benzyl alcohol, and benzyl methyl ether

Abstract

The thermal reaction of hexafluoropropene with diphenylmethane gives the 1 : 1 adduct Ph₂CHCF₂CHFCF₃(4a) and the rearranged adduct PhCH₂CF₂CFPhCF₃(5a)via benzylic hydrogen abstraction. Analogous 1 : 1 adducts are formed from benzyl alcohol in low yield, i.e. PhCH(OH)CF₂CHFCF₃(4e) and HOCH₂CF₂CFPhCF₃(5b), but the reaction is complicated by decomposition of the alcohol to benzaldehyde, toluene, and water followed by the formation of the toluene–hexafluoropropene adduct PhCH₂CF₂CHFCF₃(4c). A similar decomposition is observed with benzyl methyl ether and compound (4c) is the only fluorinated product isolated. With n-butylbenzene the 1 : 1 adduct PhCHPrⁿCF₂CHFCF₃ is formed in relatively low yield due to rearrangement of the intermediate radical PhCHPrⁿCF₂ĊFCF₃ by a 1,5-hydrogen shift followed by β-scission to give the radical PhĊHCF₂CHFCF₃ and propene and hence (4c) and the cyclobutane CF₃·[graphic omitted]HMe (8a), respectively. With isobutylbenzene the only 1 : 1 adduct isolated is PhCH₂CMe₂CF₂CHFCF₃, although benzylic hydrogen abstraction does occur as shown by the formation of compounds (4c) and (8a). 1 : 1 Adducts are not detected in the products from the reaction with S-butylbenzene; the intermediate radical PhCMeEtCF₂ĊFCF₃ undergoes (i) cyclisation to give the indan (12), (ii) decomposition to give the olefin CF₂:CMeEt and the radical PhĊFCF₃ and (iii) rearrangement followed by β-scission to give ethylene and the radical PhĊMeCF₂CHFCF₃.