(1) Preparation of sodium 3,8-dimethyl-5-isopropylchrysanthemum-1-sulfonate
Under ice bath conditions, 4 mmol of guaiacol and 2 mL of acetic anhydride (Ac2O) were added to a 25 mL pear-shaped flask. Subsequently, a mixture of 1 mL of concentrated sulfuric acid (H2SO4) and 2 mL of acetic anhydride (Ac2O) was slowly added dropwise through a constant-pressure dropping funnel (with a drying tube fitted at the top). After the dropwise addition, the reaction mixture was stirred at room temperature for about 2 hours, during which the progress of the reaction was monitored by thin layer chromatography (TLC) until the feedstock completely disappeared. Upon completion of the reaction, the mixture solution was poured into 4 mL of water and the pH was adjusted to 8-9 by dropwise addition of sodium hydroxide (NaOH) solution.Subsequently, the mixture solution was cooled to promote the formation of a precipitate, filtration was carried out, and the precipitate was washed sequentially with cold water and petroleum ether, and was dried to give 1.05 g of a blue solid product. The yield was 87.5% and the melting point was 106-107 °C.
