N-bromobutanimide → 7-Bromo-1,3,4,5-tetrahydro-2H-1-benzazepin-2-one

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Reaction Steps

To a solution of the title compound from Example 2 Step B (17.0 g, 106 mmol) in N,N-dimethylformamide (500 mL) was added N-bromosuccinimide (25.2 g, 141 mmol) at room temperature, and then the mixture was refluxed for 16 hours. The reaction mixture was diluted with ethyl acetate (1 L), and the separated organic layer was washed with 0.1 M aqueous sodium hydroxide solution and saturated aqueous sodium chloride solution, dried over Na2SO4, filtered and concentrated. Purification by flash chromatography on silica gel (petroleum ether:ethyl acetate=12:1 to 3:1) provided a crude product that was recrystallized from ethyl acetate and petroleum ether (v:v=1:10) to give the title compound: LCMS m/z=241 [M+2+H]+. 1H NMR (400 MHz, d6-DMSO): δ 9.56 (s, 1H), 7.46 (s, 1H), 7.37 (d, J=8.4 Hz, 1H), 6.87 (d, J=8.4 Hz, 1H), 2.65 (m, 2H), 2.12-2.07 (m, 4H).

Provenance & Evidence