Rare Earth Triflate-Catalyzed Addition Reactions of Acylhydrazones with Silyl Enolates. A Facile Synthesis of Pyrazolone Derivatives

Abstract

In the presence of a catalytic amount of a rare earth triflate, benzoylhydrazones reacted with silyl enolates to afford the corresponding β-N′-benzoylhydrazino esters in high yields. The hydrazino esters thus obtained were readily converted to pyrazolone derivatives by treatment with a base. A three-component reaction between an aldehyde, an acylhydrazine, and a silyl enolate was also performed successfully.