Polyfluoro-compounds based on the cycloheptane ring system. Part 4. Reactions of nucleophiles with dodeca- and with 1H-undeca- fluorocyclohept-1-ene; decafluorocycloheptyne as a reactive intermediate

Abstract

Dodecafluorocycloheptene exchanged its vinylic fluorines with nucleophiles; it gave 1H-undeca- and 1H,2H-deca- (with sodium borohydride), and 1-methylundeca- and 1,2-dimethyldeca- -fluorocycloheptene (with methyl lithium). No isomeric products were detected. 1 Methylundecafluorocycloheptene and lithium aluminium hydride afforded 1H-2-methyldecafluorocyclohept-1-ene. Dodecafluorocycloheptene and ammonia gave a little 1-amino-undecafluorocycloheptene, and 1-amino-3-iminononafluorocyclohept-1-ene, the latter being easily hydrolysed to the 3-one. 1H-Undecafluorocyclohept-1-ene did not give simple addition-elimination with methyl lithium; 1,2-dimethyloctafluorocyclohepta-1,3-diene was the product generally isolated, with 1,2,4-trimethylheptafluorocyclohepta-1,3-diene if methyl lithium was in excess. Methyl lithium in the presence of furan gave a Diels-Alder adduct in good yield, 8,11-epoxy-2,2,3,3,4,4,5,5,6,6-decafluorobicyclo-[5,4,0]undeca-1(7), 9(10)-diene. Oxidation of this gave decafluoropimelic acid. This is clear evidence for exchange of hydrogen by lithium in the starting olefin, followed by loss of lithium fluoride, to give decafluoro-cycloheptyne as a transient intermediate.