Due to the wide range of biological activities that they exhibit, isoxazolines and their derivatives have attracted considerable attention. Moreover, from a synthetic point of view, isoxazolines have found many utilities and are precursors of imino alcohols, hydroxyketones or amino alcohols. Isoxazoline N-oxides, precursors of isoxazolines, are also interesting and have found applications as biologically active compounds In the course of our work on the synthesis of β-aminocyclopropane phosphonates through the cyclopropanation of the (1,2-dibromoethyl)-phosphonate with nitroalkanes, we were interested in reversing the selectivity of this C-alkylation toward the O-alkylation to prepare isoxazoline N-oxides. A comprehensive study was undertaken to establish the parameters that reverse this selectivity. To control the O-alkylation we prepared an α-tosylate vinylphosphonate which, according to the HSAB theory, favors the O-alkylation adduct. Thus a series of 5-phosphono isoxazoline N-oxides was prepared and reduced to produce 5-phosphono isoxazolines in two steps. This new approach appear to be more efficient that the classical methods. These results will be presented in this communication.

Selective cyclization of ambident nitronate anions: C- vs. O-alkylation

251st National Meeting (2016)

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