Synthesis of Intermediate 4: 2-bromobenzyl bromide (250 mg, 1.00 mmol), sodium methanesulfinate (303 mg, 2.97 mmol) and DMF (2.5 mL) were added to a 10 mL conical flask. The reaction flask was sealed and the reaction was stirred at 60 °C for 1 hour. After completion of the reaction, it was cooled to room temperature, water was added and extracted with ethyl acetate (3×). The organic phases were combined, washed sequentially with water (2×) and saturated saline (1×), dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to give 235 mg of white solid product (94% yield). Thin layer chromatography (TLC) showed Rf = 0.34 (unfolding agent: ethyl acetate/petroleum ether, 1:2). The structure of the product was confirmed by the following characterization data: 1H NMR (CDCl3) δ 7.67-7.63 (m, 1H), 7.61 (dd, J = 7.7 Hz, 1.5 Hz, 1H), 7.40 (td, J = 7.6 Hz, 0.9 Hz, 1H), 7.27 (td, J = 7.8 Hz, 1.6 Hz, 1H), 4.52 (s 2H), 2.82 (s, 3H); 13C NMR (CDCl3) δ 133.4, 133.1, 130.8, 128.5, 128.3, 125.0, 60.4, 39.9; ESI-MS m/z 270.9 ([M + Na]+).
