Water → 7-methyl-2,3-dihydro-1,5-benzothiazepin-4(5H)-one

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Reaction Steps

6-Methyl-2,3-dihydro-4H-1-benzothiopyran-4-one (2g, 10.9 mmol) was dissolved in 80% ethanol (73 mL) and to this was added hydroxylamine hydrochloride (840 mg, 12.05 mmol) and sodium acetate (990 mg, 12.03 mmol). This mixture was heated at reflux for 3 hours. Water (150 mL) was added and then extracted with dichloromethane (3×100 mL), washed with brine (75 mL), water (75 mL), dried (sodium sulfate) and concentrated to residue. The residue was taken up in polyphosphoric acid (10 mL) and heated at reflux for 1 hour. Ice chips were added and water was added (100 mL) this was stirred for 1 hour. A solid formed and was filtered and purified by flashcolumn chromatography on 20 g of silica gel, eluting with (50%, 60%, and 70%) ethyl acetate in hexanes to give 7-methyl-2,3,4,5-tetrahydrobenzo[b]1,4-thiazepin-4-one (500 mg, 30%). 1H NMR (CDCl3, 300 MHz): δ7.87 (s-broad, 1H), 7.47 (d, 1H, J=7.7 Hz), 6.98 (d, 1H, J=8.1 Hz), 6.91 (s, 1H), 3.42 (t, 2H, J=6.9 Hz), 2.62 (t, 2H, J=6.9 Hz), 2.35 (s, 3H) ppm.

Provenance & Evidence