Benzo[b]thiophene-2-carboxylic acid (1-A, 14.4 g, 80.6 mmol) was used as starting material and mixed with N,N-diisopropylethylamine (15.5 mL, 88.6 mmol) and diphenylphosphoryl azide (20.8 mL, 96.7 mmol) in tert-butanol (150 mL). The reaction mixture was heated to reflux for 8 hours. Upon completion of the reaction, the solvent was removed by vacuum evaporation. The resulting residue was purified by silica gel fast column chromatography using dichloromethane as eluent to afford the target product tert-butyl benzo[b]thiophene-2-yl-carbamate (1-B) as a colorless solid (18.9 g, 94% yield). The structure of the product was confirmed by 1H-NMR (DMSO-d6) and mass spectrometry (MS): 1H-NMR (DMSO-d6) δ 1.50 (s, 9H), 6.78 (s, 1H), 7.16 (d, J=7.5Hz, 1H), 7.27 (d, J=7.5Hz, 1H), 7.58 (d, J=7.5Hz, 1H), 7.77 ( d, J=7.5Hz, 1H), 10.70 (br s, 1H); MS: m/z 250.2 (MH+).
![tert-butyl benzo[b]thiophen-2-ylcarbaMate](/CAS/GIF/89673-36-9.gif)