Sulfuric Acid → 3-Chloro-o-cresol

A solution of concentrated sulphuric acid (7.3 mL) in water (97 mL) was added to 3-chloro-2-methylaniline (0.84 mL, 7.06 mmol) and the mixture heated at 90° C. until solution was achieved. The reaction mixture was cooled to 0° C. and a solution of sodium nitrite (510 mg, 12.75 mmol) in water (5 mL) was added dropwise. The reaction mixture was allowed to warm to ambient temperature over 2 h. Excess sodium nitrite was destroyed by the addition of urea. The resultant mixture was added to a solution of concentrated sulphuric acid (5.0 mL) in water (55 mL), heated to 90° C. and stirred at this temperature for a further 1 h. The resultant product mixture was filtered through dicalite and extracted with dichloromethane (2×200 mL). The organic phase was washed with NaHCO3 (aq.), dried (MgSO4) and evaporated under reduced pressure to afford the desired product (830 mg, 83%) as an off-white solid.