Zn(OAc)2/US system for the synthesis of 1,8-dioxo-octahydroxanthene derivativesa.
Reaction conditions: dimedone or 1,3-cyclohexanedione (2 equiv.), aldehydes (1 equiv.); the yields were calculated after recrystallization in diethyl ether/n-hexane in (6 : 4).