Trifluoroacetic acid → (S)-1-(7,8-Difluoro-1,2,3,4-tetrahydrocyclopent[b]indol-4-yl)-2-propylamine fumarate

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Reaction Steps

A solution of (S)-4-[2-(tert-butoxycarbonylamino)propyl]-7,8-difluoro-1,2,3,4-tetrahydrocyclopent[b]indole (0.4 g, 1.1 mmol) and trifluoroacetic acid (5 mL) in dichloromethane (15 mL) was stirred at room temperature for 1 h. The mixture was made basic by the addition of aqueous sodium hydroxide solution (2 N), then extracted with dichloromethane (3×50 mL). The organic extracts were combined, dried (magnesium sulfate), filtered and concentrated in vacuo to give an orange oil. The oil was dissolved in 2-propanol (5 mL) and the solution was heated to boiling then fumaric acid (0.38 g, 3.3 mmol) was added. The mixture was cooled to room temperature and filtered The filter-cake was washed (2-propanol, ether) and dried in vacuo to give the title compound (0.89 g, 68%) as a pale orange solid. mp. 154-156° C. (dec.); NMR δH (400 MHz, DMSO-d6) 1.13 (3H, d, J 7 Hz), 2.43-2.52 (2H, m), 2.78-2.94 (4H, m), 3.5-3.57 (1H, m), 4.13 (1H, d, J 8 Hz), 4.29 (1H, dd, J 6.5 Hz), 6.55 (2H, s), 7.01-7.10 (1H, m) and 7.26-7.31 (1H, m).

Provenance & Evidence