Microwave assisted green synthesis of α, ά bis (substituted benzylidene) alkanones

The catalytic application of NbCl5 as a heterogeneous catalyst was explored for the synthesis of α, ά- bis (substituted- benzylidene) alkanones under solvent-free conditions. The results showed that aldehydes bearing electron–releasing substituents on phenyl-ring favored the formation of product in good to excellent yields with reaction times ranging between 3 and 7 min. In addition, furfural, cinamaldehyde, thiophene-2-carbaldehyde and 5-methylthiophene-2-carbaldehyde were investigated in aldol reaction, and the results showed excellent yields. The microwave irradiation gave excellent yields at lower reaction time compared to room temperature (1.5-5 h) and thermal conditions (80 ºC, 15-45 min). The microwave irradiation afforded selectively cross aldol products.