2,6-Pyridinedicarboxylic acid as an efficient and mild organocatalyst for the one-pot synthesis of xanthene derivative

Simple and efficient protocols have been developed for the one-pot synthesis of aryl-14H-dibenzo[a,j]xanthenes and 1,8-dioxo-octahydro-xanthenes. (i) A cost-effective, simple and convenient procedure for the synthesis of aryl-14H-dibenzo[a,j]xanthenes has been developed via a one-pot condensation from substituted benzaldehydes (1 equiv) and β-naphthol (2 equiv) in the presence of 2,6-pyridinedicarboxylic acid (2,6-PDCA) under solvent-free conditions. (ii) The one-pot condensation of substituted benzaldehydes (1 equiv) and 5,5-dimethyl-1,3-cyclohexanedione (dimedone) (2 equiv) in the presence of 2,6-pyridinedicarboxylic acid (2,6-PDCA) under solvent-free conditions leads to 1,8-dioxo-octahydro-xanthenes. In these protocols several advantages such as: Excellent yields, very short reaction times, easy work-up, simple methodology and ease of preparation and regeneration of the catalyst are offered. In these protocols several advantages such as: Excellent yields, very short reaction times, easy work-up, simple methodology and ease of preparation and regeneration of the catalyst are offered.