Antimony trichloride/SiO2 promoted synthesis of 9-ary-3,4,5,6,7,9-hexahydroxanthene-1,8-diones

Antimony trichloride absorbed on silica gel (SbCl3/SiO2) has been found to be an efficient catalyst for the synthesis of 9-ary-3,4,5,6,7,9-hexahydroxanthene-1,8-diones by condensation of aromatic aldehydes and 5,5-dimethyl-1,3-cyclohexanedione under solvent-free conditions. The present methodology offers several advantages such as high yields, short reaction times, simple operation and convenient work-up.