Efficient synthesis of 1,2,4-oxadiazine-5-ones via [3+3] cycloaddition of in situ generated aza-oxyallylic cations with nitrile oxides

1,2,4-Oxadiazin-5-ones were prepared via [3+3] cycloaddition of in situ generated aza-oxyallylic cations with nitrile oxides in good yields and excellent functional group compatibility. This efficient transformation is metal-free and is promoted by an inorganic base Cs2CO3. In addition, this reaction features simple-operation, mild conditions, and high regioselectivity. (C) 2018 Elsevier Ltd. All rights reserved.