General procedure for the synthesis of tert-butyl 2-aminophenylcarbamate from di-tert-butyl dicarbonate and o-phenylenediamine:
1. In a dry reaction flask, o-phenylenediamine (22 g, 200 mmol) and triethylamine (30 mL) were dissolved in THF (150 mL) and stirred until completely dissolved.
2. Prepare a solution by dissolving di-tert-butyl dicarbonate (44 g, 200 mmol) in THF (50 mL).
3. Slowly add the di-tert-butyl dicarbonate solution prepared in step 2 dropwise to the solution in step 1 at room temperature, keeping stirring during the dropwise addition.
4. after the dropwise addition, continue to stir the reaction mixture at room temperature for 15 hours.
5. upon completion of the reaction, the reaction mixture was concentrated to remove most of the solvent.
6. Ethyl acetate was added to the concentrated mixture and the resulting white solid was collected by filtration. 7.
7. The collected solid was dried under reduced pressure to give 21 g tert-butyl 2-aminophenylcarbamate.
8. The filtrate was further concentrated to give another solid which was filtered with ethyl acetate and dried, again under reduced pressure, to give 11 g of tert-butyl 2-aminophenylcarbamate.
9. The two obtained products were combined to give an overall yield of 76%.
Product characterization: 1H-NMR (400 MHz, DMSO-d6) δ 1.48 (s, 9H), 4.84 (s, 2H), 6.55 (td, J = 7.6, 1.4 Hz, 1H), 6.70 (dd, J = 7.6, 1.3 Hz, 1H), 6.86 (td, J = 7.6, 1.5 Hz, 1H), 7.20 (d, J = 7.6 Hz, 1H), 8.30 (br s, 1H).
