Cycloaddition reaction of 4-oxo-4H-pyrazole 1,2-dioxides with epoxynaphthalene. X-ray analysis of the cycloadduct and some comments on cycloaddition behavior

The crystal structure of the cycloadduct of 2,5-bis(methoxy- carbonyl)-4-exo-4H-pyrazole 1,2-dioxide with epoxynaphthalene was elucidated. The result indicates that the cycloadduct resulted from the direct 1,3-dipolar cycloaddition