Hydrochloric Acid → 5-methoxy-6-nitro-2,3-dihydro-1H-indole

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Reaction Steps

A roundbottom flask equipped with a reflux condenser, mechanical stirrer and thermowell was charged with 1-acetyl-5-(methyloxy)-6-nitro-2,3-dihydro-1H-indole (954 g, 4.04 mol) produced in accordance with Step C, immediately above, and aqueous 6N hydrochloric acid (9.5 L). The resulting suspension was heated to reflux for 4 hrs (became clear solution after 2 hrs). The reaction mixture was allowed to cool to room temperature then sodium hydroxide (50% w/w) was added to adjust the pH to 10. The resulting mixture was extracted with ethyl acetate (3×10L). The combined organic layers were washed with saturated potassium carbonate solution (10 L) and brine (10 L), then dried over sodium sulfate, evaporated in vacuo to afford 5-(methyloxy)-6-nitro-2,3-dihydro-1H-indole (737 g, 94%), which was used for the next step without further purification. 1H-NMR (DMSO, 300 MHz) δ 7.11 (s, 1H), 6.87 (s, 1H), 5.59 (brs, 1H), 3.78 (s, 3H), 3.43 (t, 2H), 2.97 (t, 2H).

Provenance & Evidence