Br[C:2]1[S:6][C:5]([CH:7]=[O:8])=[CH:4][CH:3]=1.[C:9]1(B(O)O)[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=1.C([O-])([O-])=O.[Na+].[Na+].CCOCC>C1COCC1.C1C=CC([P]([Pd]([P](C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)([P](C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)[P](C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)=CC=1>[C:9]1([C:2]2[S:6][C:5]([CH:7]=[O:8])=[CH:4][CH:3]=2)[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=15-Bromothiophene-2-carboxaldehyde (1.0 g, 5.2 mmol) is added to a solution of tetrakis(triphenylphosphine)palladium(0) (180 mg, 0.16 mol) in degassed THF (10 mL). The resulting solution is stirred for 5 minutes and then a solution of phenylboronic acid (760 mg, 6.2 mmol) in THF (10 mL) is added followed by aqueous Na2CO3 (2M, 5.2 mL). The mixture is heated at reflux for 24 h. The reaction mixture is allowed to cool, poured into ether, and washed twice with water. The ether layer is dried over Na2SO4 and concentrated in vacuo. The crude product is purified by flash column chromatography (1:1 hexanes/CH2Cl2) to yield 900 mg (91%) of 5-phenylthiophene-2-carboxaldehyde. 1H NMR (300MHz, CDCl3)δ7.38-7.45, 7.65-7.68, 7.73, 9.88.
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