Synthesis
General procedure for the synthesis of 4-nitroisoxazole from isoxazole: ammonium nitrate (1.8 g, 22.5 mmol) was added to a solution of trifluoroacetic anhydride (7 mL, 50.7 mmol) of isoxazole (1 g, 14.5 mmol) in batches of 0.3 g each, and the temperature of the reaction was controlled to be between 25 and 30 °C. After the addition was completed, the reaction mixture was slowly poured into ice water and extracted with dichloromethane (15 mL x 4). The organic phases were combined, washed with water and the aqueous layer was then extracted with dichloromethane. The combined dichloromethane extracts were dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give a yellow-green oil. The oily material was ground with hexane under the condition of cooling to 50 ℃, a solid was precipitated, and 4-nitroisoxazole was obtained by filtration (0.72 g, 44% yield).
References
[1] Journal of Organic Chemistry, 1987, vol. 52, # 13, p. 2714 - 2726
[2] Helvetica Chimica Acta, 1989, vol. 72, p. 556 - 569
[3] Patent: WO2009/154769, 2009, A1. Location in patent: Page/Page column 37-38
[4] Zhurnal Obshchei Khimii, 1959, vol. 29, p. 535,538; engl. Ausg. S. 533
[5] Patent: WO2011/38572, 2011, A1. Location in patent: Page/Page column 76
