Sulfuric Acid → 6-tert-Butyl-4-chloro-m-cresol

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The starting compound 2-tert-butyl-4-chloro-5-methyl-phenol was prepared by t-butylation in the following manner: 4-chloro-3-methyl-phenol (10.0 g, 70 mmol) was dissolved in glacial acetic acid (30 mL) at ambient temperature. tert-Butanol (10.1 mL, 1.5 equivalents) was added, and subsequently 95% sulfuric acid (3.75 mL, 1 equiv.). The reaction vessel was closed with a drying tube and heated at 50° C. After 1 d, additional amounts of tert-butanol (5 mL) and sulfuric acid (1.8 mL) were added and heating was continued. After 3 d, dichlormethane (150 mL) was added, and the solution was washed three times with saturated aqueous sodium chloride (150 mL). Drying and evaporation of the solution provided 14.9 g of a pale yellow oil. Pure 2-tert-butyl-4-chloro-5-methyl-phenol was obtained by flash chromatography (silica/toluene-heptane 7:3) as a colourless oil, 1H NMR (CDCl3): δ 7.19 (s, 1H), 6.52 (s, 1H), 4.70 (s, 1H), 2.26 (s, 3H), 1.37 (s, 9H); TLC (silica/toluene-heptane 7:3) Rf=0.45.

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