La(OTf)₃ catalyzed reaction of salicylaldehyde phenylhydrazones with β-ketoesters and activated alkynes: facile approach for the preparation of chromenopyrazolones

Abstract

A facile approach has been developed for the preparation of chromenopyrazolones (<bold>5a–o</bold>, <bold>7a–k</bold>) by the reaction of salicylaldehyde phenylhydrazones (<bold>3a–o</bold>) with β-ketoesters (<bold>4a</bold>, <bold>4f–g</bold>) and activated alkynes (<bold>6a–e</bold>) in the presence of La(OTf)₃ with good yields.