Microwave assisted solvent free synthesis of α,ά-bis (arylidene) cycloalkanones by sulfated zirconia catalyzed cross aldol condensation of aromatic aldehydes and cycloalkanones

The catalytic application of sulfated zirconia as solid Brønsted acid catalyst was explored for cross aldol condensation reactions (Claisen Schmidt reaction). The synthesized catalyst was highly active for solvent free synthesis of α,ά-bis(arylidene)cycloalkanones by cross aldol condensation of aromatic aldehydes with cycloalkanones. The microwave assisted synthesis resulted increased yields of the products (79–99%) at significantly lower reaction temperature (120–140 °C) and reaction time (20 min) as compared to the synthesis by thermal heating (63–96% yield at 170 °C after 4 h). The microwave irradiation afforded selectively cross aldol products. The catalyst could be easily regenerated and reused several times with similar efficiency.