An efficient route to 1,8-dioxo-octahydroxanthenes and -decahydroacridines using a sulfated zirconia catalyst

Sulfated zirconia results to be a very efficient catalyst for the synthesis of 1,8-dioxo-octahydroxanthenes and 1,8-dioxo-decahydroacridines without tedious work-up procedures. While 1,8-dioxo-octahydroxanthenes are prepared from aldehyde and 5,5-dimethyl-1,3-cyclohexenedione (dimedone), 1,8-dioxo-decahydroacridines are prepared from this reactant mixture with amines. This method provides a mild catalytic protocol for the synthesis of functionalized xanthene and acridine derivatives. The catalysts were characterized by XRD, FT-IR, TGA-DSC, SEM-EDAX and surface acidity and showed excellent re-usability up to 6 consecutive cycles.