Sodium Carbonate → 4-Bromo-3-(4-hydroxyphenyl)thiophene-2-carbaldehyde

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A mixture of 3,4-dibromothiophene-2-carbaldehyde (see Intermediate 1 (see Example 15 for Intermediate synthesis)) (2.0 g, 7.5 mmol), 4-hydroxyphenylboronic acid (Scheme II, 8A, X1=4-hydroxyphenyl) (1.0 g, 7.5 mmol), Na2CO3 (1.6 g, 15 mmol), and Pd(PPh3)4 (431 mg, 0.37 mmol) in toluene/EtOH/H2O (30 mL, 5:3:2) was heated to 80° C. and stirred overnight under nitrogen. When TLC indicated that the starting material was consumed, the mixture was diluted with water, neutralized to pH=4-5 with HCl (1M), extracted with EtOAc, concentrated, and purified by column chromatography (PE:EtOAc=20:1) to give 4-bromo-3-(4-hydroxyphenyl)thiophene-2-carbaldehyde (Scheme II, 8, X1=4-hydroxyphenyl) (350 mg, yield 17%) as a white solid. 1H NMR (DMSO-d6 400 MHz): δ9.90 (s, 1H), 9.53 (s, 1H), 8.33 (s, 1H), 7.33 (d, J=8.4 Hz, 2H), 6.91 (d, J=8.4 Hz, 2H).

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