Grignard Reagent-Mediated Conversion of an Acyl Nitroso-anthracene Cycloadduct to a Nitrone

An intramolecular hetero-Diels−Alder cycloadduct of an acyl
nitroso compound and a 9,10-dimethyl anthracene derivative
was prepared as a potential nitroxyl (HNO) donor. This
compound did not release HNO under any of the conditions
tested. Treatment of this cycloadduct with excess MeMgCl
resulted in the formation of a nitrone, whose structure was
confirmed by X-ray crystallography. A mechanism where
MeMgCl acts as a nucleophile, strong base, and Lewis acid
possibly explains the formation of this product.