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Synthesis of 2-isoxazolines

Recent Literature

tert-Butyl hypoiodite (t-BuOI), generated in situ from t-BuOCl and NaI, is a powerful reagent for the cycloaddition of oximes to alkenes or alkynes, leading to various isoxazolines or isoxazoles under mild conditions.
S. Minakata, S. Okumura, T. Nagamachi, Y. Takeda, Org. Lett., 2011, 13, 2966-2969.

The dehydration of primary nitro compounds can be performed by bases in the presence of dipolarophiles. Among the organic bases examined, DABCO gave the best results. The reaction is applicable to activated nitro compounds and to phenylnitromethane and affords isoxazoline derivatives in higher yields compared with those of other methods. The reaction, however, is not compatible with nitroalkanes.
L. Cecchi, F. De Sarlo, F. Machetti, Eur. J. Org. Chem., 2006, 4852-4860.

Iodobenzene diacetate efficiently oxidizes aldoximes to nitrile oxides in MeOH containing a catalytic amount of TFA. Nitrile oxides may be trapped in situ with olefins in a bimolecular or an intramolecular mode. Tandem oxidative dearomatization of phenols/intramolecular nitrile oxide cycloaddition sequences lead to useful synthetic intermediates.
B. A. Mendelsohn, S. Lee, S. Kim, F. Tayssier, V. S. Aulakh, M. A. Ciufolini, Org. Lett., 2009, 11, 1539-1542.

Unprotected O-propargylic hydroxylamines undergo cyclisations when exposed briefly to silver nitrate adsorbed onto silica gel to give 4,5-dihydroisoxazoles [2-isoxazolines] in very good yields, while N-acetyl derivatives give the corresponding 2,5-dihydroisoxazoles [3-isoxazolines] in similar yields.
D. W. Knight, A. J. Proctor, J. M. Clough, Synlett, 2010, 628-632.

3-alkylpropargyl or 3-arylpropargyl hydroxylamines hydrochlorides were converted to 2-isoxazolines in good yields in refluxing methanol in the presence of K₂CO₃. Methods for 3-unsubstituted compounds and the direct transformation of a O-propargyl phthalimide into 2-isoxazolines have been developed.
L. Pennicott, S. Lindell, Synlett, 2006, 463-465.

3-Acylisoxazoles were synthesized by the reaction of alkenes or alkynes with ketones (acetone or acetophenone), as both a reagent and the solvent, by three methods: iron(III) nitrate under reflux, iron(III) salt-nitrogen dioxide (NO₂) at room temperature, and iron(III) nitrate under microwave irradiation (MW).
K.-I. Itoh, H. Sakamaki, N. Nakazato, A. Horiuchi, E. Horn, C. A. Horiuchi, Synthesis, 2005, 3541-3548.