To a solution of compound 2b (619 mg, 1 mmol) in toluene (20 mL) under argon atmosphere were added K2CO3 (276 mg, 2 mmol), phenylmethanethiol (125 mg, 1 mmol), Pd2(dba)3 (200 mg, 0.22 mmol) and Xantphos (75 mg, 0.16 mmol). Then the mixture was stirred at 115° C. for 4 h. After being cooled to rt, the reaction was diluted with water (100 mL) and extracted with EA (100 mL×2). The combined organic layers were washed with brine (100 mL×2), dried over Na2SO4 and concentrated to dryness. Purification by CC gave compound the compound 5a (200 mg; 30%) as a pale yellow solid. 1H NMR (400 MHz, CDCl3) δ: 7.36-7.32 (m, 3H), 7.28-7.07 (m, 9H), 7.01 (d, J=7.2 Hz, 1H), 6.82 (d, J=2.0 Hz, 1H), 6.66 (dd, J=8.8, 2.0 Hz, 1H), 4.75 (s, 2H), 4.04 (s, 2H), 3.06-3.00 (m, 2H), 2.84-2.78 (m, 2H), 2.44-2.38 (m, 3H), 2.09 (m, 1H), 1.24-1.18 (m, 2H), 1.11-1.08 (m, 2H). MS (ESI+) m/z: 662 [M+1]+.
