Synthesis
The general procedure for the synthesis of 7-bromoindole and pinacol ester of bis(pinacolato) borate from 7-bromoindole and pinacol ester of bis(pinacolato) borate was as follows: 7-bromoindole (20 g, 0.102 mol) was dissolved in a 1 L single-necked flask containing DMSO (100 mL), and bis(pinacolato)diboron (39 g, 0.153 mol), [1,1'-bis(diphenylphosphinato)ferrocene]dichloro palladium (Pd(dppf)Cl2, 4 g, 0.005 mol) and potassium acetate (15 g, 0.153 mol). The reaction system was heated to 85 °C and the reaction was stirred for 2 hours. After completion of the reaction, the reaction was quenched by the addition of water. The mixture was extracted three times with ethyl acetate, the organic phases were combined and dried over anhydrous sodium sulfate. After concentration under reduced pressure, the product was purified by column chromatography to afford the target product 7-indoleboronic acid pinacol ester (25 g, 0.103 mol). The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3) and mass spectrometry (ESI): 1H NMR (400 MHz, CDCl3) δ 9.29 (s, 1H), 7.82 (d, J = 7.9 Hz, 1H), 7.70 (d, J = 7.0 Hz, 1H), 7.32-7.29 (m, 1H), 7.21- 7.14 (m, 1H), 6.62-6.57 (m, 1H), 1.44 (s, 12H); MS (ESI) m/z: [M + H]+ 244.1.
References
[1] Synlett, 2003, # 8, p. 1204 - 1206
[2] Advanced Synthesis and Catalysis, 2017, vol. 359, # 19, p. 3421 - 3427
[3] Journal of the American Chemical Society, 2017, vol. 139, # 24, p. 8267 - 8276
[4] European Journal of Organic Chemistry, 2016, vol. 2016, # 27, p. 4621 - 4628
[5] Patent: JP2015/528445, 2015, A. Location in patent: Paragraph 0047; 0065
