Elsevier

Tetrahedron

Volume 53, Issue 5, 3 February 1997, Pages 1787-1796
Tetrahedron

Cycloadditions of nitrile oxides to amidoximes. A general synthesis of 3,5-disubstituted 1,2,4-oxadiazole-4-oxides.

Dedicated to Prof. Gianfranco Bettinetti on the occasion of his 72nd birthday and his retirement from teaching duties.
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Abstract

The cycloaddition of nitrile oxides to amidoximes is a general method for the sinthesis of 3,5-disubstituted 1,2,4-oxadiazole-4-oxides with the same or different substituents. The yields are only moderate since an equivalent amount of the nitrile oxide is consumed by reaction with the amine released in the fragmentation of the primary cycloadducts and reforms the amidoxime. With excess nitrile oxides the 1,2,4-oxadiazole-4-oxides undergo a disproportionation reaction to yield nitroso carbonyl intermediates and 1,2,4-oxadiazoles.

The cycloadditions of nitrile oxides to amidoximes afford 1,2,4-oxadiazole-4-oxides, 1,2,4-oxadiazoles, nitroso carbonyl intermediates and amidoximes.

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