2,4,6-Trimethylphenol → 3,4,5-Tribromo-2,4,6-trimethyl-2,5-cyclohexadienone

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The preparation of a halogenated phenol such as 4-bromomethyl-3,5-dibromo-2,6-dimethylphenol (tribromomesitol) can involve the following sequence: bromination of 2,4,6-trimethylphenol (mesitol) with 2 moles of bromine in acetic acid to prepare 3,5-dibromo-2,4,6-trimethylphenol (dibromometisol) which is isolated by precipitation with water. K. Auwers & F. Rapp, Ann., 302, 153-71 (1898) and O. Jacobsen, Ann., 195, 265-92 (1879); the dibromomesitol is brominated in acetic acid sodium acetate buffer at low temperatures to afford an intermediate, 3,4,5-tribromo-2,4,6-trimethyl-2,5-cyclohexadienone, which is isolated by fast precipitation with water and filtration; this solid slowly rearranges to tribromomesitol at room temperature, more quickly at higher temperatures. K. Fries & E. Brandes, Ann., 542, 48-77 (1939). This procedure to prepare tribromomesitol is complex and not industrially viable.

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