Compound 2

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Compound data: CIF

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

3-(2-(methylamino)-2-oxoethanoyl)-1H-indol-7-ylboronic acid S1 (3.57 g, 1 equiv) was combined with 2,2,2-trifluoroethanol (97 mL) and vigorously stirred at room temp. for 5 minutes. The heterogeneous mixture was then cooled to 0 °C and iodomesitylene diacetate (5.28 g, 1.0 equiv) was added. The reaction was stirred 5 minutes at 0 ºC, then it was warmed to room temperature and stirred 2 hours. The reaction was diluted with dichloromethane (200 mL) then stirred with 0.75 M LiClO₄ (aq) (200 mL) for 15 minutes. The layers were separated, and the organics were treated with the washing procedure twice more with fresh 0.75 M LiClO₄ (aq), with additional 2,2,2-trifluoroethanol being added as needed to keep the organic phase homogeneous. The organics were dried on magnesium sulfate, filtered and concentrated under reduced pressure. The crude material was dissolved in dichloromethane and concentrated again to remove the 2,2,2-trifluoroethanol until a red solid is obtained. The red solid was then suspended in dichloromethane and sonicated behind a blast shield for 1 hour. The mixture was then cooled to room temperature and filtered, and the collected solids were washed with dichloromethane. Drying in vacuo provided 2 (6.64 g, 84% yield) as an off white solid. ¹H NMR (500 MHz, DMSO-d₆) δ 13.08 (s, 1H), 8.98 (s, 1H), 8.80 (q, J = 4.8 Hz, 1H), 8.46 (d, J = 7.7 Hz, 1H), 7.83 (d, J = 7.7 Hz, 1H), 7.26 (t, J = 7.8 Hz, 1H), 7.17 (s, 2H), 2.77 (d, J = 4.8 Hz, 3H), 2.59 (s, 6H), 2.26 (s, 3H). ¹³C NMR (125 MHz, DMSO-d₆) δ 182.46, 163.43, 142.92, 141.28, 139.60, 135.75, 130.52, 129.76, 128.24, 125.27, 125.04, 124.17, 113.02, 97.69, 26.57, 25.65, 20.48. IR (thin film, cm^-1) 3379.0, 3228.5, 1666.6, 1642.7, 1513.0, 1431.7, 1055.1, 781.1, 618.9. HRMS (ESI-TOF) calculated for C₂₀H₂₁ClIN₂O₆ [M]⁺ m/z 447.05695, found 447.05688, difference 0.2 ppm. To prepare crystals for x-ray diffraction analysis, a saturated acetone solution (0.5 mL) of iodonium 2 in a small test tube was placed into a sealed vial containing diethyl ether. Overnight, clear crystals precipitated.