2E,2'E-3,3'-(1,4-Phenylene)bis(1-(2,5-dimethylfuran-3-yl)prop-2-en-1-one

Abstract

A bis-chalcone has been synthesized by reaction of 3-acetyl-2,5-dimethylfuran and terephthalaldehyde in ethanolic NaOH at room temperature: (2E,2'E)-3,3'-(1,4-phenylene)bis(1-(2,5-dimethylfuran-3-yl)prop-2-en-1-one) (3) was obtained in high yield. The structure of this compound was established by elemental analysis, IR, ¹H NMR, ¹³C NMR and EI-MS spectral analysis.

The Claisen-Schmidt condensation is the most important reaction for the formation of 1,3-diphenyl-2-propene-1-ones. The products, also known as chalcones, generally are synthesized by this method from suitable acetophenones and benzaldehydes. Chalcones are considered to be precursors of flavonoids when found as naturally-occurring compounds. The chemical importance of chalcones is extended in two branches: their biological activity, including anti-inflammatory [1], antimitotic [2], anti-leishmanial [3], anti-invasive [4], anti fungal [5], antimalarial [6] and anti-tumor [7] properties; as well as their recognized synthetic utility in the preparation of pharmacologically interesting hetero­cyclic systems such as thiazines, pyrimidines, and pyrazoles. Here we are reporting a novel bis-chalcone prepared from 3-acetyl-2,5-dimethylfuran and terephthalaldehyde. The product is assumed to exist as one E,E-diastereomer, since in the the ¹H-NMR spectrum the olefinic protons display coupling constants of 15.6 Hz indicative of the E-configuration.

A solution of 3-acetyl-2,5-dimethylfuran (2.34 mL, 0.028 mol) and terephthalaldehyde (2.0 g, 0.014 mol) in an ethanolic solution of NaOH (6.0 g in 10 mL of ethanol) was stirred for 20 h at room temperature. The solution was poured into ice cold water of pH~2 (pH adjusted by HCl). The solid was separated and dissolved in CH₂Cl₂, washed with a saturated solution of NaHCO₃ and evaporated to dryness. The residue was recrystallized from methanol/chloroform to give a yellow solid:

Yield: 78%; m.p. 182 °C.

EI-MS m/z (rel. int.%): 376 (76) [M+1]⁺,

IR (KBr) vmax cm⁻¹: 2956 (C-H), 1655 (C=O), 1567 (C=C).

¹H NMR (600 MHz, CDCl₃) δ: 7.72 (d, 2H, J = 15.6 Hz, C=CH), 7.22 (d, 2H, J = 15.6 Hz, CO=CH), 7.63 (s, 4H, Ar-H), 6.34 (s, 2H, 2×furan-H), 2.62 (s, 6H, 2×CH3), 2.30 (s, 6H, 2×CH₃).

¹³CNMR (150 MHz, CDCl₃) δ: 185.65, 158.20, 150.17, 141.60, 136.70, 128.99, 125.00, 122.41, 105.54, 14.53, 13.05.

Anal. calc. for C₂₄H₂₂O₄: C, 76.99, H, 5.92, O, 17.09; Found: C, 76.95, H, 5.88, O, 19.98.