2,3-Dihydro-1,4-benzothiazine → 4-nitroso-3,4-dihydro-2H-benzo[b][1,4]thiazine

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Reaction Steps

To a solution of 3,4-dihydro-2H-1,4-benzothiazine (50.0 g, 330.8 mmol) in acetic acid (170 mL.), cooled at −10° C. in an ice/acetone bath, was added sodium nitrite (27.4 g, 397.1 mmol) in 75 mL of water over 35 min. After the addition, the mixture was warmed to room temperature and stirred for additional 1.5 hours. Cold water (150 mL) was added and the resulting mixture was extracted with dichloromethane (4×250 mL). The combined organic extracts were washed with water and brine, dried over anhydrous sodium sulfate, and concentrated to dryness under reduced pressure to give 4-nitroso-3,4-dihydro-2H-1,4-benzothiazine as a semi-solid (60.26 g, 101%), which was used in the next step without further purification. 1H NMR (300 MHz, DMSO-d6) δ2.99-3.05 (m, 2H), 4.16-4.24 (m, 2H), 7.15-7.31 (m, 3H), 7.88-7.97 (m, 1H) ppm.

Provenance & Evidence