Potassium Carbonate → 4-[(2-Chloro-4-formylphenyl)sulfanyl]-2-methylphenoxy-acetic acid ethyl ester

An oven-dried 500 mL round-bottomed flask was charged with finely powdered K2CO3 (31.8 g, 230 mmol) and anhydrous DMF (104 mL). Next, a solution of compound 10.3 (26.1 g, 115 mmol) and 3,4-dichlorobenzaldehyde (21.0 g, 120 mmol) in anhydrous DMF (52 mL) was added dropwise at 90° C., and the reaction was vigorously stirred at same temperature for 1 h. The reaction mixture was poured into 468 mL of ice-water and extracted with 3×200 mL of AcOEt. The combined organics were sequentially washed with 2×200 mL of water and 100 mL of brine, dried over Na2SO4, and concentrated to a yellow oil, which was then purified by flash chromatography (SiO2 gel 60 N, eluted with 10% AcOEt/hexane—20% AcOEt/hexane). The fractions containing only desired product were combined and concentrated to a slightly yellow oil (34.9 g). 1H NMR (300 MHz) (CDCl3) δ 9.85 (1H, s); 7.81 (1H, d, J=1.5 Hz); 7.50 (1H, dd, J=1.8, 8.1 Hz); 7.37-7.35 (2H, m); 6.80-6.74 (2H, m); 4.71 (2H, s); 4.30 (2H, q, J=7.2 Hz); 2.32 (3H, s); 1.32 (3H, t, J=7.2 Hz).