N-methyl-2-pyrrolidone → 3-nitro-7,8-dihydro-6H-5-oxa-9-aza-benzocycloheptene-9-carboxylic acid 3-dimethylamino-propyl ester

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Reaction Steps

3-Dimethylamino-propan-1-ol (346 uL, 2.92 mmol) was dissolved in N-methylpyrrolidinone (25.0 mL, 259 mmol) and sodium hydride 60% dispersion in mineral oil (93.5 mg) was added. The reaction was stirred for 5 minutes and then 3-(3-chloro-propyl)-6-nitro-3H-benzoxazol-2-one (500 mg, 1.95 mmol) was added. The reaction was stirred at room temperature for 4 hours and then partitioned between ethyl ether (100 mL) and water (50 mL). The layers were separated and the organic layer was washed twice with water (50 mL). The organic layer was dried over sodium sulfate, filtered, and concentrated under reduced pressure. Purification by basic alumina chromatography using a gradient of 0-50% EtOAc/hex as the eluting solvent to obtain 3-nitro-7,8-dihydro-6H-5-oxa-9-aza-benzocycloheptene-9-carboxylic acid 3-dimethylamino-propyl ester as a yellow oil (437 mg, 69%). LCMS (m/e) 324 (M+H); 1H-NMR (CDCl3, 400 MHz) δ 7.89-7.80 (m, 2H), 7.53-7.36 (m, 1H), 4.29-4.17 (m, 4H), 3.89-3.77 (m, 2H), 2.39-2.08 (m, 4H), 2.19 (s, 6H), 1.88-1.73 (m, 2H).

Provenance & Evidence