tert-Butyl thiophen-2-ylcarbamate

White to off-white crystalline powder

To a solution of thiophenecarboxylic acid (0.5 g, 3.90 mmol) in tBuOH (10 ml) was added Et3N (0.571 ml, 4.10 mmol) and DPPA (0.883 ml, 4.10 mmol). The solution was heated at 90 °C for 4 hours. The reaction mixture was cooled to RT, and the solvent was removed from the vacuum. The residue was treated with benzene, and the solution was washed with 5 per cent citric acid and NaHCO3. Solid was filtered off, and the filtrate was washed with brine. The organic layer was dried (MgSO4), concentrated in vacuo and the residue was purified by silica gel column chromatography (EtOAc/hexanes) to obtain tert-butyl thiophen-2-ylcarbamate (0.39 g, 50percent yield). 1H NMR (400 MHz, DMSO-d6): δ 10.4 (brs, 1H), 6.84 (dd, J = 1.6, and 5.2 Hz, 1H), 6.75 (dd, J = 4.0, and 5.6 Hz, 1H), 6.48 (dd, J= 1.6, and 4.0 Hz, 2H), 1.45 (s, 9H); MS (ESI) m/z: 222.0 (M+22+H+).