Hetero Cope-Type Hydroamination of Hetero-Allenes with Oximes Having Olefin Moieties Leading to Nitrones, Causing Intramolecular Cycloaddition

Hetero-allenes such as isocyanates, isothiocyanates, and carbodiimides reacted with oxime having olefin moieties in the manner of hetero Cope-type hydroamination to generate <i>N</i>-modified nitrones, which underwent intramolecular cycloaddition to give intramolecular cycloadducts. Among them, the reaction of isocyanates with oximes proceeded at room temperature to provide the corresponding cycloadducts in very high yields. The efficiencies of these sequential cycloadditions were directly compared by competitive reactions. As a result, the order of reactivity to oxime <b>1a</b> is isocyanate <b>2a</b>, isothiocyanate <b>3a</b>, and carbodiimide <b>6a</b>. Theoretical studies were also conducted.