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 are offered.