Hydrochloric Acid → 4-[3E-(4-Hydroxy-2-methoxy-5-thiophen-2-yl-phenyl)-acryloyl]-benzoic acid

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4-Hydroxy-2-methoxy-5-thiophen-2-yl-benzaldehyde (Ex-47B, 0.30 g, 0.86 mmol) and 4-acetylbenzoic acid (0.13 g, 0.86 mmol) were dissolved in a dimethylformamide-methanol solution (6 mL, 7:3). After complete dissolution, lithium methoxide (0.12 g, 3.3 mmol) was added and the resulting red slurry was stirred in the dark at room temperature for 18 h. The mixture was diluted with water (15 mL), acidified with a 1 N hydrochloric acid solution, and extracted with ethyl acetate (4×25 mL). The combined organic extracts were dried over sodium sulfate and evaporated to dryness. The crude oil was subjected to silica gel chromatography (CH2Cl2:MeOH, 20:1) to yield an orange solid containing residual amounts of starting acid. The solid was taken up in ethyl alcohol (5 mL) to remove acid impurity and the resulting precipitate was collected on filter paper and dried in vacuo to yield 0.010 g (5%) of the title compound as an orange solid, mp 243° C. (dec). 1H-NMR (300 MHz, DMSO-d6) δ 8.18–8.23 (m, 3H), 8.06–8.09 (m, 2H), 8.02 (s, 1H), 7.85 (d, 1H, J=15.6 Hz), 7.68 (d, 1H, J=3.6 Hz), 7.47 (d, 1H, J=5.1 Hz), 7.11 (dd, 1H, J=5.1, 3.6 Hz), 6.67 (s, 1H), 4.13 (s, 1H), 3.89 (s, 3H). MS (ESI) m/z=381 ([M+H]30 , 100%). HRMS (ESI) Calcd. for C21H16O5S: 381.0796. Found: 381.0800.

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