Reaction of Polyhaloalkyl-Substituted Chromones, Pyrones, and Furanones with Salicylaldehydes as a Direct Route to Fused 2H-Chromenes

Polyhaloalkyl-substituted chromones, γ-pyrones, and β-furanones react with salicylaldehydes in the presence of piperidine to give a wide variety of fused 2H-chromenes in good yields. This novel annulation reaction presumably proceeds by a tandem intermolecular oxa-Michael addition and subsequent intramolecular Mannich condensation.