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To a solution of the product of step C (50 mg, 0.13 mmol) and trifluoroacetic acid (0.75 mL) at 0° C. was added triethylsilane (64 μL, 0.40 mmol). The reaction was allowed to warm to ambient temperature over 14 h then quenched by addition of aqueous sodium bicarbonate solution. The mixture was extracted with dichloromethane (2×20 mL) and the combined organic extracts dried over anhydrous Na2SO4, filtered, and the filtrate concentrated in vacuo. The residue was purified by flash column chromatography (SiO2, 9:1 to 1:1 hexanes/ethyl acetate) to give ethyl 9-bromo-7-chloro-4,5-dihydro-1H-benzofuro[2,3-d]azepine-3(2H)-carboxylate (48 mg, 96%) as a colorless oil: 1H NMR (CDCl3, 300 MHz) δ 7.45-7.38 (m, 1H), 7.35 (d, J=1.4 Hz, 1H), 4.20 (q, J=7.1 Hz, 2H), 3.78-3.67 (m, 4H), 3.20-3.10 (m, 2H), 2.88-2.75 (m, 2H), 1.29 (t, J=7.0 Hz, 3H).

1. customthen quenched by addition of aqueous sodium bicarbonate solution
2. extractionThe mixture was extracted with dichloromethane (2×20 mL)
3. dry with materialthe combined organic extracts dried over anhydrous Na2SO4
4. filtrationfiltered
5. concentrationthe filtrate concentrated in vacuo
6. customThe residue was purified by flash column chromatography (SiO2, 9:1 to 1:1 hexanes/ethyl acetate)