Hydrochloric Acid → 3-oxo-3,4-dihydro-2H-1,4-benzoxazine-7-sulfonyl chloride

Participants

Reaction Conditions

Reaction Steps

Into a 500 mL 3-necked round bottom flask was placed a solution of 7-amino-2H-benzo[b][1,4]oxazin-3(4H)-one (5 g, 28.96 mmol) in CH3CN (200 mL). To the above was added acetic acid (24.9 g) dropwise with stirring, while cooling to a temperature of 0° C. To the above was added HCl (16.2 g) dropwise with stirring, while cooling to a temperature of 0° C. This was followed by the addition of a solution of NaNO2 (2.52 g, 36.52 mmol) in H2O (2 mL), which was added dropwise with stirring, while cooling to a temperature of 0° C. The resulting solution was allowed to react, with stirring, for 30 minutes while the temperature was maintained at 0-5° C. in a bath of H2O/ice. This was followed by and maintained with an atmosphere of sulfur dioxide, the resulting solution was allowed to react, with stirring, for an additional 2 hours while the temperature was maintained at 0-5° C. in a bath of H2O/ice. To the mixture was added CuCl2.2H2O (5.11 g, 29.97 mmol), while cooling to a temperature of 0-5° C. The resulting solution was allowed to react, with stirring, maintained with an atmosphere of sulfur dioxide for an additional 2 hours while the temperature was maintained at 0-5° C. in a bath of H2O/ice. The resulting solution was allowed to react, with stirring, overnight while the temperature was maintained at room temperature. The reaction progress was monitored by TLC (petroleum ether/ethyl acetate=1:1). The reaction mixture was then quenched by the adding 200 mL of H2O/ice. The resulting solution was extracted one time with 500 mL of ethyl acetate and the organic layers combined. Then the mixture was washed 3 times with 200 mL of brine. The mixture was dried over MgSO4 and concentrated by evaporation under vacuum using a rotary evaporator. The residue was dissolved in 100 mL of CH2Cl2. A filtration was performed. The filtrate was concentrated by evaporation under vacuum using a rotary evaporator. This resulted in 0.9 g (11%) of 3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-7-sulfonyl chloride as a yellow solid. 1HNMR (400 MHz, CDCl3) δ 4.73 (s, 2H), 7.00 (m, 1H), 7.28 (d, 1H), 7.71 (d, 1H), 8.27 (s, 1H).

Provenance & Evidence