Synthesis of coumarin derivatives via knoevenagel condensation under microwave irradiation

Coumarin is a therapeutic agent, found naturally as a secondary metabolite in plants, bacteria, fungi, and essentialoils, and can be chemically synthesized. The Knoevenagel reaction is one of the most useful C=C bond formation methodsinvolving the condensation between benzaldehyde and activated methylenes in the presence of an amine. This study aims to synthesize coumarin with microwave-assisted via Knoevenagel condensation. This study synthesized coumarin from 2-hydroxybenzaldehyde and various activated methylenes with various catalysts. The mixture was irradiated in the microwave for several reaction times (60 s, 70 s, 80 s, 10 minutes, and 15 minutes) at 5-10 intervals. TLC monitored the reaction using n-hexane and ethyl acetate (8:2). The product was purified by recrystallization. The product was tested for purity by TLC and melting point, followed by structural elucidation by UV-Vis spectrophotometry. It was found that the optimal time for 3-acetylcoumarin synthesis was 60 s and 10 minutes for ethyl coumarin 3-carboxylate.