Hydroximoyl fluorides as the precursors of nitrile oxides: synthesis, stability and [3 + 2]-cycloaddition with alkynes?

Organic & Biomolecular Chemistry Pub Date: 2018-11-15 DOI: 10.1039/C8OB02721H

Abstract

The transformation of hydroximoyl fluorides to nitrile oxides for [3 + 2]-cycloaddition with alkynes has been achieved for the first time. The hydroximoyl fluorides used in this work appeared to be not stable, which was proved by a series of experiments. A DFT calculation was performed to better understand the properties of hydroximoyl fluorides. Although not stable, the hydroximoyl fluorides could be successfully converted to the corresponding nitrile oxides for in situ [3 + 2]-cycloaddition with alkynes to yield the isoxazoles. Furthermore, it was feasible to conduct [3 + 2]-cycloaddition reaction without purification after the synthesis of hydroximoyl fluorides from gem-difluoroalkenes. By investigating a class of interesting yet previously rarely explored fluorinated compounds, this work sheds new light on the stability and reactivity of a C–F bond on a C[double bond, length as m-dash]N double bond.

Graphical abstract: Hydroximoyl fluorides as the precursors of nitrile oxides: synthesis, stability and [3 + 2]-cycloaddition with alkynes
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