RSC Adv., 2016,6,11023

Catalyzed Claisen–Schmidt reaction by protonated
aluminate mesoporous silica nanomaterial focused
on the (E)-chalcone synthesis as a biologically
active compound

The mesoporous silica structure (MSN) was synthesized using the sol–gel method followed by aluminum
grafting and protonation and was then denoted as HAlMSN (Si/Al ¼ 18.9). N2 physisorption confirmed
the mesoporous structure with a pore diameter of 3.38 nm. 27Al NMR showed the presence of
framework and extra-framework aluminum structures, which led to the formation of strong Lewis and
Brønsted acidic sites. HAlMSN catalyzed the synthesis of (E)-chalcones through the Claisen–Schmidt
reaction. Chalcone derivatives have been applied as biologically active compounds with anti-cancer,
anti-inflammatory and diuretic pharmacological activities. The products were obtained via reactions on
the protonic acid sites of HAlMSN. The significant advantages of this reaction are high yield, easy work
up, short reaction time and also compatibility with various organic solvents. The products were obtained
in an excellent conversion of 97% at 298 K. The results show that the electron donating substituents
exhibit higher conversion in comparison to electron withdrawing substituents. The stability of the
catalyst was investigated by reusing it five times for (E)-chalcone production and there was only a slight
decrease in its catalytic activity. The highest product of (E)-chalcone was observed with a 1 : 2 molar
ratio of benzaldehyde/acetophenone. A comparative study in chalcone synthesis using the
heterogeneous catalysts demonstrated that HAlMSN has a significantly high activity at low temperature.