Hydrochloric Acid → 3-Oxo-3,4-dihydro-2H-1,4-benzothiazine-6-carbaldehyde

Temperature

0 °C

6-Hydroxymethyl-4H-benzo[1,4]thiazin-3-one. To a 0° C. suspension of 3-oxo-3,4-dihydro-2H-benzo[1,4]thiazine-6-carboxylic acid (400 mg, 2 mmol) in THF (19 mL) was added Et3N (0.32 mL, 2 mmol) and the resulting solution was treated with iso-butylchloroformate (0.3 mL, 2 mmol). The resulting suspension was stirred at 0° C. for 2 h, filtered and the solid was washed with THF. The filtrate was cooled to 0° C., treated with NaBH4 (150 mg, 4.3 mmol) and slowly treated with H2O (10 mL). The resulting suspension was warmed to RT and stirred for 18 h. The suspension was neutralized using 1 N HCl and diluted with H2O (100 mL). The organic layer was extracted with EtOAc (3×200 mL). The combined organic layers were dried (MgSO4), filtered and concentrated. The resulting residue was purified on SiO2 (0-10% CH3OH/CH2Cl2) to provide 330 mg (89%) of the title compound as a white solid. MS (ESI): exact mass calculated for C9H9NO2S, 195.04; m/z found, 196.1 [M+H]+. 1H NMR (500 MHz, CD3OD): 7.26 (d, J=7.9, 1H), 7.01-6.98 (m, 2H), 4.55 (s, 2H), 3.40 (s, 2H).

1. filtrationfiltered
2. washthe solid was washed with THF
3. temperatureThe filtrate was cooled to 0° C.
4. temperatureThe resulting suspension was warmed to RT
5. stirringstirred for 18 h
6. extractionThe organic layer was extracted with EtOAc (3×200 mL)
7. dry with materialThe combined organic layers were dried (MgSO4)
8. filtrationfiltered
9. concentrationconcentrated
10. customThe resulting residue was purified on SiO2 (0-10% CH3OH/CH2Cl2)

ORD record

ord-a9bfaf0c5d134547bc96a5863b2ed8b5

Source dataset

uspto-grants-2012_08

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08242275B2