On water: Free catalysis approach for the synthesis of nitrones from hydroxamic acids and dimethy/diethyl acetylenedicarboxylate

Benzohydroxamic acid reacts with dimethyl acetylenedicarboxylate in the presence of 10 mol% NaOAc to generate (E)-N-(1,4-dimethoxy-1,4-dioxobutan-2-ylidene)-1-phenylcarboxamide oxide in good-to-excellent yield in water at room temperature for 2 h, which supplies a simple, efficient and environmentally friendly method to synthesize a wide range of nitrones. The benefits of this strategy not only conform to the requirment of green chemisty, but also possess atom economy.