Synthesis of Intermediate 2 via NaOH Reaction

A 4.3 g quantity of sodium hydroxide was dissolved in 10 times its weight of water, stirred, and then combined with 8 g of intermediate 2. The mixture was reacted at 90°C–100°C for 3–6 h, monitored using the TLC plate (DCM: MeOH = 10:1). Upon completion of the reaction, the mixture was subsequently cooled to room temperature, following which impurities were extracted once using dichloromethane (DCM). Verification was performed via TLC analysis. The aqueous phase was then adjusted to a pH range of 3–5 using 3 N hydrochloric acid, resulting in the precipitation of solid material. After filtration by suction, the solid was rinsed with water and dried at 60°C for approximately 4 h, yielding a 94.0% yield.