Synthesis
A) 38 g (0.16 mol) of 1-acetyl-5-bromoindoline, 31 g of concentrated hydrochloric acid and 41 g of ethanol were added to the reaction flask and stirred thoroughly to obtain reaction mixture I; B) reaction mixture I was reacted at 78 °C for 4 h. Complete disappearance of the raw materials was confirmed by chromatographic monitoring; C) the reaction mixture was neutralized using 55 g of sodium hydroxide solution; D) the organic phase J and the aqueous phase K were separated; E) the organic phase J was extracted three times using 445 g of chloroform. K; E) Organic phase J was extracted three times with 445 g of chloroform. The organic layers were combined and the solvent was recovered to give 30.74 g of 5-bromodihydroindole in 98.04% yield and ≥99% purity.
References
[1] Patent: CN106432040, 2017, A. Location in patent: Paragraph 0108-0113; 0135-0140; 0162-0167
[2] European Journal of Medicinal Chemistry, 2006, vol. 41, # 1, p. 88 - 100
[3] Tetrahedron Letters, 2004, vol. 45, # 25, p. 4827 - 4830
[4] Patent: CN106966950, 2017, A. Location in patent: Paragraph 0022
[5] Patent: US2011/98311, 2011, A1
