Bicyclic Pyrazolidinone Derivatives from Diastereoselective Catalytic 3 + 3-Cycloaddition Reactions of Enoldiazoacetates with Azomethine Imines

A highly regio- and diastereoselective synthesis of bicyclic pyrazolidinone derivatives by rhodium(II) acetate catalyzed 3 + 3-annulation with enoldiazoacetates and azomethine imines has been achieved in high yield. A vinylogous reaction of the metal enol carbene with the azomethine imine initiates 3 + 3-cycloaddition, whereas reaction at the carbene center effects N-N-cleavage of the azomethine imine.