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

Temperature

110 °C

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).

1. temperatureAfter overnight heating
2. temperaturethe mixture was cooled
3. extractionextracted with DCM (2×50 mL)
4. washthe combined organics were washed with water (50 mL) and brine (50 mL)
5. customdried and conc. in vacuo
6. customThe residue was chromatographed (120 g SiO2, ISCO, 0-20% EtOAc:Hex)

ORD record

ord-b27372d9ed9e476ab94f945b01976a0a

Source dataset

uspto-grants-2013_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08552186B2