[Et3NH][HSO4] catalyzed efficient and green synthesis of 1,8-dioxo-octahydroxanthenes

A simple and efficient procedure for synthesis of 1,8-dioxo-octahydroxanthenes by one-pot condensation of aromatic aldehydes with 5,5-dimethyl-1,3-cyclohexanedione under solvent-free conditions using ionic liquid [Et3NH][HSO4] as catalyst is described. The procedure offers several advantages including cleaner reaction profiles, use of easily available, cheap, recyclable and environmentally benign nature of catalyst, high yields, and simple experimental and work-up procedures.

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► [Et3NH][HSO4] was used as catalyst for the synthesis of 1,8-dioxo-octahydroxanthenes.
► The reaction conditions are mild and eco-friendly.
► Protic ionic liquid [Et3NH][HSO4] is efficient, green, cheap and recyclable.
► The plausible catalytic mechanism was proposed.