Potassium Hydroxide → 2,3,4,5-Tetrahydro-7-nitro-1,5-benzoxazepine

Participants

Reaction Conditions

Reaction Steps

1.00 M of Potassium hydroxide in Water (25 mL) was added to 2-Nitro-7,8-dihydro-6H-5-oxa-9-aza-benzocycloheptene-9-carboxylic acid ethyl ester (2.84 g, 10.7 mmol) in 2-Methoxyethanol (50 mL) and the reaction was heated at 110° C. After overnight heating, the mixture was cooled, extracted with DCM (2×50 mL); the combined organics were washed with water (50 mL) and brine (50 mL), dried and conc. in vacuo. The residue was chromatographed (120 g SiO2, ISCO, 0-20% EtOAc:Hex) to afford 2-Nitro-6,7,8,9-tetrahydro-5-oxa-9-aza-benzocycloheptene as an orange solid (1.64 g, 79%). 1697d) 2-Nitro-6,7,8,9-tetrahydro-5-oxa-9-aza-benzocycloheptene (278 mg, 1.43 mmol) was dissolved in Acetonitrile (15 mL) and Acetaldehyde (0.80 mL, 14 mmol) was added. Acetic acid (0.15 mL, 2.6 mmol) was added, followed by Sodium triacetoxyborohydride (0.85 g, 4.0 mmol), and the mixture was stirred under an atmosphere of Nitrogen at room temperature for 1 h. The solution was diluted with ethyl acetate (50 mL) and satd. sodium bicarbonate (50 mL). The layers were separated, the organic washed with brine (50 mL) and dried over sodium sulfate. Conc. in vacuo followed by chromatography (ISCO, g SiO2, 0-50% EtOAc:Hex) afforded 9-Ethyl-2-nitro-6,7,8,9-tetrahydro-5-oxa-9-aza-benzocycloheptene as an orange oil (272 mg, 85%). 1H-NMR (CDCl3) 7.58 (m, 2H), 6.87 (d, 1H, J=8.1 Hz), 4.31 (t, 2H, J=5.2 Hz), 3.40 (t, 2H, J=5.2 Hz), 3.33 (q, 2H, J=6.8 Hz), 2.05 (tt, 2H, J=5.2, 5.2 Hz), 1.24 (t, 3H, J=6.8 Hz).

Provenance & Evidence