Synthesis
General procedure for the synthesis of 6-chloroindoline from 6-chloroindole:
1. reduction of indole to indoline: 6-chloro-1H-indole (2 g, 0.013 mol) was dissolved in acetic acid (10 mL) under nitrogen protection.
2. Sodium cyanoborohydride (1.24 g, 1.5 eq.) was added to the above solution and the reaction was stirred at room temperature for 20 min.
3. Upon completion of the reaction, the reaction mixture was diluted with ethyl acetate.
4. The organic phase was separated by extraction using 5N aqueous sodium hydroxide solution.
5. The organic phase was dried with magnesium sulfate, filtered and concentrated to give the crude product 6-chloro-2,3-dihydro-1H-indole (2.35 g, 116% yield).
6. The product was analyzed by material spectrum (ES, m/z): 154.0 (M + 1).
References
[1] Patent: WO2003/76398, 2003, A2. Location in patent: Page/Page column 41
[2] Patent: US2011/21500, 2011, A1. Location in patent: Page/Page column 49
[3] Patent: JP2015/193573, 2015, A. Location in patent: Paragraph 0043
[4] Patent: WO2012/143726, 2012, A1. Location in patent: Page/Page column 129
[5] Journal of Medicinal Chemistry, 2015, vol. 58, # 16, p. 6574 - 6588
