Reaction Steps
To a solution of 3 (25 mg, 0.05 mmol) in EtOAc (5 mL) was added stannous chloride dihydrate (58 mg, 0.26 mmol). The resulting mixture was refluxed for one hour under N2. The reaction mixture was poured onto ice (5 g), and basified with a saturated NaHCO3 solution to pH 8. The white milky mixture was filtered through a Celite pad to remove tin oxides. The organic layer from the filtrate was dried over MgSO4, filtered, and then concentrated in vacuo. MPLC purification (Hex:EtOAc/4:1) of the crude product gave the desired intermediate methyl (2-bromo-5-(3-amino-4-(phenylethynyl)benzoyl)thiophen-3-yl)acetate as a yellow foam (21 mg, 90%). 1H NMR (400 MHz, CDCl3) δ 7.55 (m, 2H), 7.50 (s, 1H), 7.48 (d, J=1.6 Hz, 1H), 7.38 (m, 3H), 7.17 (m, 2H), 4.40 (brs, 2H), 3.73 (s, 3H), and 3.66 (s, 2H); 13C NMR (100 MHz, CDCl3) δ 186.7, 170.3, 148.1, 143.4, 138.1, 135.9, 135.1, 132.4, 131.8, 129.0, 128.7, 122.9, 122.8, 118.8, 114.5, 112.3, 97.6, 85.3, 52.6, and 35.0; HRMS-ESI calcd C22H16BrNO3S [M+Na] 475.9926. found 475.9923. To a 250 mL flask containing freshly distilled toluene (50 mL) was added methyl (2-bromo-5-(3-amino-4-(phenylethynyl)benzoyl)thiophen-3-yl)acetate (2.93 g, 6.45 mmol) and indium tribromide (1.14 g, 3.22 mmol) under N2. The resulting mixture was refluxed for one hour. The solvent was removed in vacuo. MPLC purification (Hex:EtOAc/4:1) of the crude product gave 4 as a yellow solid (2.50 g, 85%). 1H NMR (400 MHz, CDCl3) δ 9.38 (brs, 1H), 7.98 (s, 1H), 7.69 (d, J=7.8 Hz, 2H), 7.58 (m, 2H), 7.47 (s, 1H), 7.40 (t, J=7.5 Hz, 2H), 7.30 (m, 1H), 6.80 (s, 1H), 3.65 (s, 3H), and 3.59 (s, 2H); 13C NMR (100 MHz, CDCl3) δ 187.4, 170.5, 144.2, 142.3, 136.5, 135.7, 134.9, 133.3, 131.8, 130.9, 129.4, 128.8, 125.9, 121.9, 120.4, 113.5, 100.3, 52.6, and 35.2.
