Synthesis of 1,2,4-oxadiazolidines via [3+2] cycloaddition of nitrones with carbodiimides

An efficient [3+2] cycloaddition of nitrones and carbodiimides has been developed. This 1,3-dipolar cycloaddition features high regioselectivity, mild and metal-free conditions, excellent functional group compatibility, and a broad substrate scope. The X-ray structures of two regio-isomers confirmed the regioselectivity of this transformation.