反应详情

N-tert-butylphenylnitrone (44.8 g, 0.25 mol) was dissolved in toluene (134 g) in a 500 ml bottle. Sulphuric acid (27.5 g, 95 to 97%, 0.27 mol, 1.1 equiv.) was diluted in water (134 g) and added to the reaction bottle. The two-phase mixture was then heated to +50° C. and stirred vigorously for approximately 2 h. At that time, GC indicated that only 0.2 area % of N-tert-butylphenylnitrone remained. After cooling to +20° C., the dark red organic phase was discarded and the clear, yellow water phase was extracted once with toluene (46 g). To the remaining water phase was then added acetic acid (14.8 g, 0.25 mol, 1.0 equiv.) followed by sodium hydroxide (45% aqueous solution) until the pH of the water phase was approximately 5.5. Ethyl acetate (224 g) was then added and the mixture was stirred vigorously. The organic phase was then separated and the aqueous phase was extracted once more with ethyl acetate. The combined organic fractions were then evaporated to leave an oil (35.2 g). This material was purified by distillation under reduced pressure. A stable distillation point was achieved at 19 mbar/ +78° C. Fraction 1, retrieved below +70° C., contained 2.7 g and fraction 2, collected between +70° C. and +80° C., con a highly viscous oil (28.7 g, 76%) that crystallized as a white solid upon standing. pKa 6.4 Chromatographic purity (GC): 99.4 area %

1. additionadded to the reaction bottle
2. temperatureThe two-phase mixture was then heated to +50° C.
3. temperatureAfter cooling to +20° C.
4. extractionthe clear, yellow water phase was extracted once with toluene (46 g)
5. stirringthe mixture was stirred vigorously
6. customThe organic phase was then separated
7. extractionthe aqueous phase was extracted once more with ethyl acetate
8. customThe combined organic fractions were then evaporated