Synthesis and bromodemercuration of some permercurated arenes

Pentabromonitrobenzene, pentabromobenzoic acid, pentabromobenzamide, pentabromoacetanilide, barium pentabromobenzenesulphonate, 1, 2, 4, 5 - tetrabromo-3-chloro-6-(trifluoromethyl)benzene, 2, 3, 5, 6-tetrabromo-4-methoxytoluene 2, 3, 5, 6-tetrabromo-4-methoxybenzamide, methyl 2, 3, 5, 6-tetra-bromo-4-methoxybenzoate, and 1, 2, 5-tribromo-3, 4-dichloro-6-fluorobenzene have been synthesized in good yield by bromodemercuration of the corresponding fully mercurated (permercurated) arenes, e.g. C₆(HgO₂CCF₃)₅NO₂, which were prepared by reaction of an excess of molten mercuric trifluoroacetate with suitable arenes at c. 180-245°. Permercuration of p-methoxybenzoic acid was accompanied by complete decarboxylation giving, after bromodemercuration, pentabromo(methoxy)-benzene, which was also obtained in low yield from preparations of methyl 2, 3, 5, 6-tetrabromo-4-methoxybenzoate and 2, 3, 5, 6-tetrabromo-4-methoxybenzamide. Conditions have been devised for conversion of phenylmercuric chloride into either a pentamercurated or a hexamercurated benzene derivative, and hence into pentabromo-or hexabromobenzene. The results establish permercuration/bromodemercuration as a simple and versatile route to polybromobenzene.