Oxidative cycloaddition of aldoximes with unsaturated substrates provides an efficient approach to the formation of heterocyclic compounds. More specifically, various isoxazoles can be easily prepared by the oxidative cycloaddition of aldoximes and alkynes in the presence of hypervalent iodine(III) reagents. Oxidation of aldoximes by hypervalent iodine (III) compounds will produce nitrile oxides which further react with respective alkyne substrates through a cycloaddition reaction resulting in various isoxazole products. Here, we report an efficient synthetic approach for preparation of various isoxazoles using Koser’s reagent. Several isoxazoles were prepared regioselectively by [hydroxy(tosyloxy)iodo]benzene mediated oxidative cycloaddition of aldoximes with trans-4-(dimethylamino)-3-buten-2-one (scheme 1). The oxidative cycloaddition proceeds at room temperature resulting in moderate to high yields. Structures of several isoxazole derivatives were established by X-ray crystallography. These isoxazole derivatives are stable compounds that have the potential to be useful for biological purposes.

Regioselective synthesis of isoxazoles by hypervalent iodine(III) reagent mediated oxidative cyclization

2019 Spring National Meeting

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