Trifluoroacetic anhydride → 2,2,2-Trifluoro-1-(7-methoxy-8-nitro-1,2,4,5-tetrahydro-benzo[d]azepin-3-yl)-ethanone

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Reaction Steps

Into a 1-neck round-bottom flask 7-methoxy-2,3,4,5-tetrahydro-1H-benzo[d]azepine (17.00 g, 0.096 mol) was dissolved in acetonitrile (100 mL). Trifluoroacetic anhydride (47.4 mL, 0.34 mol) was added at −20° C. After 10 minutes potassium nitrate (9.7 g, 0.096 mol) was added at the same temperature, and the reaction mixture was stirred for 1.5 hours. The reaction was quenched by addition of diluted NaHCO3, and allowed to warm to room temperature. Partition between saturated aqueous Na2CO3 and dichloromethane, extraction, drying (MgSO4), filtration, and concentration, provided the crude product. Flash chromatography separation on SiO2 with dichloromethane (100%) provided 2,2,2-trifluoro-1-(7-methoxy-8-nitro-1,2,4,5-tetrahydro-benzo[d]azepin-3-yl)-ethanone (11.5 g, 38%) and 2,2,2-trifluoro-1-(7-methoxy-6-nitro-1,2,4,5-tetrahydro-benzo[d]azepin-3-yl)-ethanone (7.5 g, 25%). 2,2,2-Trifluoro-1-(7-methoxy-8-nitro-1,2,4,5-tetrahydro-benzo[d]azepin-3-yl)-ethanone: 1H-NMR (CDCl3; amide rotamers observed) δ 7.72 (1H), 6.89 (1H), 3.95 (3H), 3.65-3.85 (4H), 2.95-3.07 (4H); LC/MS (ESI+): 319.20 (M+H). 2,2,2-Trifluoro-1-(7-methoxy-6-nitro-1,2,4,5-tetrahydro-benzo[d]azepin-3-yl)-ethanone: 1H-NMR (CDCl3; amide rotamers observed) δ 7.24 (1H), 6.85 (1H), 3.88 (s, 3H), 3.65-3.81 (4H), 2.80-3.05 (4H).

Provenance & Evidence