General procedure for the synthesis of 2,6-di-tert-butyl-4-nitrophenol from 2,6-di-tert-butylphenol: 2,6-di-tert-butylphenol (8 g, 39 mmol) was dissolved in 25 ml of cyclohexane at 10 °C. A mixed acid (5 ml) consisting of nitric acid and acetic acid mixed 1:1 by volume was slowly added dropwise to the reaction system while maintaining the reaction temperature at 10 °C. After the dropwise addition was completed, the reaction mixture was stirred at room temperature for 15 minutes. Upon completion of the reaction, the precipitate formed was collected by filtration and washed sequentially with water and pentane. The resulting crude product of 2,6-di-tert-butyl-4-nitrophenol (6.34 g, 65% yield) was dried in an oven and used in subsequent steps without further purification. The product was a light yellow powder with a melting point of 167-168 °C. 1H NMR (CDCl3, 100 MHz, δ): 1.48 (s, 18H, 2×t-Bu), 5.93 (s, 1H, OH), 8.13 (s, 2H, Ar-H).
