Fluoro cyclohexanes-III : 1H:4H/2H- and 1H/2H:4H-nonafluoro cyclohexane and derived compounds

Abstract

Two nonafluoro cyclohexanes of b.p. 92° and 101°, made by fluorination of benzene, 1 have each been dehydrofluorinated to give the same six unsaturated products. These were identified by oxidation and other studies as 3H:4H- and 4H:5H-octafluoro cyclohexene, 1H-1:4-, 1H-1:3-, and 2H-1:3-heptafluoro cyclohexadiene, and hexafluorobenzene, 2 thus indicating a 1H:2H:4H-structure for the saturated precursors. The stereochemistry of the adjacent > CHF groups was established by resolution, via the brucine salt, of the 3H:4H-hexafluoroadipic acid obtained by oxidation of the 4H:5H-mono-olefin, showing that the hydrogens were trans. The complete stereochemistry of the nonafluorides was suggested by the dehydrofluorinations and confirmed by further fluorination 3 to give known decafluoro cyclohexanes. Treatment of 4H/5H-octafluoro cyclohexene with lithium aluminium hydride in diethyl ether gave 1H,4H/5H-heptafluoro cyclohexene, a precursor of pentafluorobenzene. 4