1,3‐Dipolar Cycloadditions: Synthesis of Fused Bicyclic Pyrazolidinones Through Azomethine Imine Cycloaddition With Oxabicyclic Alkene

ABSTRACT The catalyst‐free 1,3‐dipolar cycloaddition of an oxabicyclic alkene with N,N′‐cyclic azomethine imine has been developed. Various fused N,N′‐bicyclic pyrazolidinone derivatives were conveniently synthesized in good yield with high diastereoselectivity. We utilized an oxabicyclic alkene as a dipolarophile for the first time in the [3 + 2] cycloaddition of N,N′‐cyclic azomethine imine. The relative configuration of the cycloaddition product was determined by single‐crystal X‐ray diffraction analysis.