Reaction Steps
A solution of 23 (250 mg, 0.67 mmol) in 10 mL of THF-CH3OH (1:1) at -40° C. was treated with a catalytic amount of TsOH-H2O (20 mg) and NIS (180 mg, 0.80 mmol, 1.2 equiv) in 2 mL of THF. The reaction mixture was stirred under Ar at -40° C. for 1 h, and then warmed to 0° C. Additional TsOH-H2O (10 mg) and NIS (75 mg, 0.5 equiv) were added. After the reaction mixture was stirred for 1 h at 25° C., it was quenched with the addition of 5 mL of saturated aqueous NaHCO3 and extracted with Et2O (4×15 mL). The combined organic layer was washed with saturated aqueous Nacl and dried (Na2SO4). PCTLC (2 mm SiO2, 0-10% EtOAc-hexane gradient) afforded 27 (230 mg, 338 mg theoretical, 68%) as a solid: mp 177° C. dec (needles, EtOAc-hexane); 1H NMR (CDCl3, 400 MHz) δ8.38 (d, 1H, J=1.5 Hz), 8.26 (d, 1H, J=8.6 Hz), 8.21 (s, 1H), 7.52 (dd, 2H, J=1.0, 7.8 Hz), 7.47 (dd, 1H, J=1.5, 8.6 Hz), 7.45-7.35 (m, 3H), 7.33 (br s, 1H), 5.26 (s, 2H), 1.59 (s, 9H); 13C NMR (CDCl3, 100 MHz) δ155.4, 152.5, 140.2, 137.0, 135.9, 134.2, 128.7, 128.4, 127.9, 125.1, 125.0, 124.3, 119.0, 112.2, 102.2, 81.8, 78.8, 70.7, 28.3; IR (film) vmax 3383, 2978, 2228, 1732, 1600, 1563, 1495, 1397, 1366, 1331, 1230, 1154, 987, 879, 735 cm-1 ; FABHRMS (NBA-CsI) m/z 632.9674 (M+ +Cs, C23H21IN2O3 requires 632.9651).
