[C:1]1([OH:7])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.[H-].[Na+].[N+]([C:13]1[S:17][C:16]([CH:18]=[O:19])=[CH:15][CH:14]=1)([O-])=O.O>CS(C)=O>[O:7]([C:13]1[S:17][C:16]([CH:18]=[O:19])=[CH:15][CH:14]=1)[C:1]1[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1Phenol (3.3 g, 35 mmol) is added in portions to a suspension of 60% NaH (1.3 g, 35 mmol) in DMSO (100 mL). The resulting mixture is stirred for 30 min then 5-nitrothiophene-2-carboxaldehyde (5 g, 32 mmol) is added. After 1 hr the reaction mixture is poured into water (1L) and washed with ether (4×500 mL). The combined organic layers are dried over Na2SO4, filtered and evaporated to dryness. The resulting material is dissolved in MeOH and passed through a column (2.5 cm×20 cm) of Amberjet 4400 (OH− form). The eluent is dried in vacuo then evaporated twice from CH3CN. The crude product is purified by column chromatography in EtOAc-hexanes (1:1) to yield 5-phenoxy-thiophene-2-carboxaldehyde (304 mg, 5%). 1H NMR (300 MHz, CDCl3) δ 6.52, 7.20, 7.27, 7.45, 7.55, 9.75.
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