2,3-Dimethylaniline → tert-butyl 6-[2-(2,3-dimethylanilino)-2-oxoethyl]-1,4,5,6-tetrahydroazepino[4,5-b]indole-3(2H)-carboxylate

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Reaction Steps

(3-(tert-butoxycarbonyl)-2,3,4,5-tetrahydroazepino[4,5-b]indol-6(1H)-yl)acetic acid (3.38 mmol) was dissolved in THF (20 mL) and 2,3-dimethylaniline (0.43 mL, 0.43 g, 3.6 mmol, 1.05 equiv.), dimethylaminopyridine (0.415 g, 3.40 mmol, 1.01 equiv.), and diisopropylcarbodiimide (0.60 mL, 0.48 g, 3.8 mmol, 1.13 equiv.) were added. The reaction mixture was stirred at rt under N2 for 18 h. The reaction mixture was taken up in EtOAc (100 mL) and this solution was washed with 10% aqueous citric acid (2×50 mL), 5% aqueous NaHCO3 (2×50 mL), and brine (50 mL). The organic layer was dried over MgSO4, filtered, and concentrated. The crude product (1.7223 g) was chromatographed (SiO2 187 g, eluted with 10:1 toluene:acetone followed by 9:1 toluene:acetone) to give tert-butyl 6-[2-(2,3-dimethylanilino)-2-oxoethyl]-1,4,5,6-tetrahydroazepino[4,5-b]indole-3(2H)-carboxylate (1.1066 g) in 67% yield. 1H NMR (300 MHz, CD3OD) δ 1.50, 2.01-2.03, 2.27, 2.29-3.12, 3.66-3.75, 3.75-3.83, 5.03, 7.04-7.19, 7.37, 7.49; MS (ESI+) for C27H33N3O3 m/z 448.1 (M+H)+.

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