Synthesis
The general procedure for the synthesis of tert-butyl 5-aminoindoline-1-carboxylate from tert-butyl 5-nitro-1H-indole-1-carboxylate is as follows:
XII; tert-butyl 5-amino-2,3-dihydro-indole-1-carboxylate; 6.8 g of tert-butyl 5-nitro-1H-indole-1-carboxylate was dissolved in 120 mL of methanol. To this solution was added 600 mg of 10% palladium carbon catalyst, followed by a hydrogenation reaction at room temperature for 1.5 hours. Upon completion of the reaction, the catalyst was removed by filtration and the solvent was evaporated under reduced pressure. The final product was 6 g of tert-butyl 5-aminoindoline-1-carboxylate in 100% yield of the theoretical value. The product was analyzed by mass spectrometry (ESI+) and showed m/z = 235 [M + H]+.
References
[1] Patent: WO2008/113760, 2008, A2. Location in patent: Page/Page column 92
[2] Patent: US2017/50964, 2017, A1. Location in patent: Paragraph 0734
[3] Bioorganic and Medicinal Chemistry Letters, 2007, vol. 17, # 23, p. 6481 - 6488
[4] Synthesis, 2007, # 10, p. 1509 - 1512
