Microwave-Driven Claisen-Schmidt Preparation Of 4-Nitrochalcone And 2,4-Dimethoxy-4-Nitrochalcone: Yield, Purity, and Spectroscopic Differentiation

Abstract

Abstract

Chalcones remain valuable synthetic intermediates in pharmaceutical chemistry because their alpha,betaunsaturated carbonyl system allows efficient structural diversification and supports broad biological screening.This study evaluated microwave-assisted Claisen-Schmidt condensation for preparing 4'-nitrochalcone and 2,4dimethoxy-4'-nitrochalcone and compared the influence of a 2,4-dimethoxy-substituted acetophenone precursor on isolated yield and structural confirmation.Equimolar aryl ketone substrates were reacted with 4'-nitrobenzaldehyde in ethanolic sodium hydroxide, stirred for 5 min, and irradiated at 160 W for 2 min.Products were purified by recrystallization and evaluated by melting point, thin-layer chromatography, FTIR, and 1H-NMR spectroscopy.4'-Nitrochalcone was obtained as yellow crystals in 58.19 +/-1.052%yield with a melting range of 165.7-166.2degrees C. Its FTIR spectrum showed bands at 3076 cm-1 for aromatic C-H, 1668 cm-1 for C=O, 1597 and 1444 cm-1 for aromatic C=C, 1514 and 1334 cm-1 for NO2, and 844 cm-1 for para substitution; 1H-NMR confirmed trans olefinic coupling with J = 16.9Hz. 2,4-Dimethoxy-4'-nitrochalcone was obtained in 19.07 +/-0.63%yield with a melting range of 184.7-185.2degrees C. Its FTIR spectrum showed C=O at 1662 cm-1, NO2 bands at 1512 and 1332 cm-1, C-O-C absorptions at 1298 and 1282 cm-1, and para substitution at 831 cm-1; 1H-NMR confirmed two methoxy singlets and trans geometry with J = 13.3Hz.Microwave irradiation enabled rapid formation of both nitrochalcones, while the dimethoxy-substituted substrate produced a substantially lower isolated yield.