ChemInform Abstract: Copper‐Catalyzed Aerobic Oxidative Cyclization of Hydrazones to Pyrazolidinones.

Abstract

Copper-Catalyzed Aerobic Oxidative Cyclization of Hydrazones to Pyrazolidinones. -Cascade [3 + 2]-cycloaddition/oxidation reactions of N-aryl hydrazones lead to the various bicyclic pyrazolidinones with moderate to good yields. Aryl substituents at the diazo group is essential. The authors suggest that the amount of air in the reaction system despite working under routine argon conditions is sufficient for oxidation. The reaction carried out on air is difficult to control. Under prolonged heating of (Ia) a complex cascade of multiple oxidation and cyclization steps leads to a tetracyclic product (III). -(DOS SANTOS, A.; EL KAIM, L.; GRIMAUD*, L.; RONSSERAY, C.; Eur. J. Org. Chem. 2011, 17, 3117-3121, http://dx.