Study of an in situcarbocationic system formed from trityl chloride (Ph3CCl) as an efficient organocatalyst for the condensation of dimedone with arylaldehydes

Organocatalysttrityl chloride (Ph3CCl), by in situ formation of trityl carbocation with inherent instability, efficiently catalyzes the condensation of dimedone (5,5-dimethyl-1,3-cyclohexanedione) (2 equiv.) with arylaldehydes (1 equiv.) under solvent-free conditions to afford 9-aryl-1,8-dioxo-octahydroxanthenes in high to excellent yields and in relatively short reaction times. Formation of the carbocationic system is confirmed by studying IR, 1H NMR and UV spectra according to the literature. Moreover, a plausible mechanism based on the literature and observations is proposed for the reaction.