1,3‐Dipolar cycloaddition reactions of nitrile oxides and nitrile imines with 2‐methoxyvinyl phenyl ketone

Abstract Nitrile oxides react regioselectively with 2‐methoxyvinyl phenyl ketone 1 to give 4‐benzoylisoxazoles 4 via elimination of methanol from the primary cycloadducts 3. After heating with an excess of nitrile oxide bis‐cycloadducts 5 were also formed. Reactions of nitrile imines with 1 are less regioselective yielding both 4‐benzoylpyrazoles 9 and 5‐benzoytpyrazoles 10, whereas no bis‐cycloadducts were isolated.