Fe(HSO4 )3 /SiO2: an efficient and heterogeneous catalyst for one-pot synthesis of 2-aryl-chromene-4-ones (flavanones)

Abstract

Silica ferric hydrogensulphate is an efficient heterogeneous catalyst for cyclisation of 2-hydroxychalcones to their corresponding flavanones (chromanone). This intramolecular oxa-Michael reaction was carried out in high yields in the presence of electron donating and electron withdrawing groups in the chalcone structure. Also, we found that aniline can act as an organic co-catalyst in direct synthesis of flavanones from 2-hydroxyacethophenone and aldehydes in the presence of Fe(HSO4)3/SiO2. Flavanones were prepared in high yields in a new catalytic system with similar substituted effect in the indirect cyclisation method. The catalyst in all the above reactions is reusable without significant decreases in its activity after four times of recycling.