FLUORINATIONS WITH POTASSIUM TETRAFLUOROCOBALTATE. PART VIII. FLUORINATIONS OF TOLUENE AND OF PHENYLACETIC ACID

Article abstract of DOI:10.1016/S0022-1139(00)82734-7

At 340 deg C, toluene gave five 1-trifluoromethyl-substituted compounds: -2H,4H,5H-tetrafluorocyclohexa-1,4-diene (IX); -2H-4H/5H-hexafluorocyclohex-1-ene (X); -2H-octafluorocyclohex-1-ene (IV); -nonafluorocyclohex-1-ene (III); also perfluoromethylcyclohexane (II): traces of perfluorocyclohexane (I) were found.The 1-difluoromethyl-substituted analogues of these five were also obtained: - compounds XII, XV, VIII, VI, and V, respectively.A further five 1-difluoromethyl-substituted derivatives were found : -nonafluorocyclohex-3-ene (VII); an inseparable mixture of the -2H,4H- and -2H,5H-heptafluorocyclohex-1-enes (XI); -2H-3H/4H-hexafluorocyclohex-1-ene (probably) (XIV); and (difluoromethyl)benzene (XIII). Structures of the unknown products were established by analysis and by nmr and ir spectroscopy.Further, the key intermediate (XII) was oxidized to difluoromalonic acid, whilst compound IV was dehydrofluorinated, to give 2H-(difluoromethyl)tetrafluorobenzene (XXI), together with an inseparable mixture of 2H,4H- and 2H,5H-1-(difluoromethyl)pentafluorocyclohexa-1,4-diene (XX).Dehydrofluorination of mixed heptafluoro-enes XI afforded 2H-1-(difluoromethyl)hexafluorocyclohexa-1,4-diene (XVIII), and mixed 2H-1- and 1H-2-(difluoromethyl)hexafluorocyclohexa-1,3-diene (XIX). Difluoromethylundecafluorocyclohexane (V) did not dehydrofluorinate.Phenylacetic acid was fluorinated likewise, and gave a similar range of products, but also one (originally an acid fluoride?) which was converted to the methyl ester of tridecafluoro(cyclohexylacetic) acid (XVII).The probable pathway of the fluorination process could be worked out.