efficient solvent free synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[a]-xanthen-11-ones and 3h-spiro[isobenzofuran-1,9'-xanthen]-3-one derivatives using cobalt hydrogensulfate as a green, heterogeneous and reusable catalyst

cobalt hydrogensulfate is an efficient catalyst for the condensation of β-naphthol, aromatic aldehydes and 5,5-dimethyl-1,3-cyclohexanedione at 120 °c to afford 9,9-dimethyl-12-phenyl-8,10,11,12-tetrahydro-9-h-benzo[a]xanthen-11-one derivatives in high yields. also, polycondensation reactions of phenols with phthalic anhydride were carried out in the presence of cobalt hydrogensulphate under solvent-free conditions. simple and convenient procedure, high conversion, reusability of catalyst, easy purification and short reaction time are the advantageous features of this method.