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.