3-(acryloylamino)-2,2-dimethylpropionaldehyde oximes underwent thermally induced 1,3-dipolar cycloaddition under mild conditions, leading to perhydroisoxazolo[4,3-c]pyridine derivatives. The features of the intramolecular oxime–olefin cycloaddition in this system and the roles of the geminal methyl groups at the 2-position and the alkenylamino nitrogen in the oxime–nitrone isomerization process are discussed based on