Water → 9-Ethyl-3-nitro-6,7,8,9-tetrahydro-5-oxa-9-aza-benzocycloheptene

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Reaction Steps

2-Ethylamino-5-nitro-phenol (2.50 g, 13.7 mmol) was azeotroped with toluene to ensure dryness, then dissolved in Tetrahydrofuran (300 mL). 3-Bromo-1-propanol (1.50 mL, 16.6 mmol), Tributylphosphine (5.5 mL, 22 mmol), and 40% w/w DEAD in Toluene (40:60, Diethyl Azodicarboxylate:Toluene, 9.6 g) were added, and the reaction was stirred under an atmosphere of Nitrogen overnight. Solvent was partially removed (300 mL removed) and the mixture was diluted with 300 mL EtOAc, then washed with satd. sodium bicarbonate (100 mL), water (2×100 mL) and brine (100 mL). The organics were dried over sodium sulfate and conc. onto 15 g SiO2 and chromatographed (ISCO, 120 g, 0-30% EtOAc:Hex) to afford [2-(3-Bromo-propoxy)-4-nitro-phenyl]-ethyl-amine as a yellow solid. [2-(3-Bromo-propoxy)-4-nitro-phenyl]-ethyl-amine was dissolved in Tetrahydrofuran (200 mL) and Sodium hydride, 60% disp. in mineral oil 0.55 g) was added. After 2 h, no reaction was observed, so N,N-Dimethylformamide (10 mL) was added. After overnight stirring, the reaction was near completion and was quenched with water, diluted with 500 mL ether then washed with water (50 mL), satd. sodium bicarbonate (2×50 mL) and brine (100 mL), dried over sodium sulfate and conc. in vacuo onto 8 g SiO2, then chromatographed (ISCO, 0-30% EtOAc:Hex, 120 g SiO2). The isolated product was ˜85% purity, with the alkyl bromide as the major impurity. The mixture was redissolved in DMF (20 mL). Potassium tert-Butoxide (0.23 g, 2.0 mmol) was added and the mixture stirred under nitrogen for 1 h, then water (100 mL) was added. The precipitate was cooled for 20 min, then collected by filtration, washing with water (2×50 mL) to give 9-Ethyl-3-nitro-6,7,8,9-tetrahydro-5-oxa-9-aza-benzocycloheptene (1.99 g, 48%). 1H-NMR (CDCl3): 7.83 (dd, 1H, J=2.5, 8.4 Hz), 7.72 (d, 1H, J=2.5 Hz), 6.61 (d, 1H, J=8.4 Hz), 4.25 (t, 2H, J=6.4 Hz), 3.60 (t, 2H, J=5.4 Hz), 3.38 (q, 2H, J=7.2 Hz), 2.11 (m, 2H), 1.25 (t, 3H, J=7.2 Hz).

Provenance & Evidence