Quantum Chemical-GuidedSteglich Rearrangement ofAzlactones and Isoxazolones

The theoretical guided evaluation of the Steglich rearrangement of azlactones and isoxazolones allowed the determination of the reactivity patterns in these heterocycles, including the factors that drive the regioselectivity towards both possible sites. These results allowed the first experimental report on the regioselective Steglich rearrangement of isoxazolones, affording the nitrogen- or carbon-acyloxy adducts.