4,5,6,7-Tetrahydro-4-oxothionaphthene → Benzo(b)thiophen-4-ol

Participants

Reaction Steps

Phenyltrimethylammonium tribromide (11.4 g) was added in portions under nitrogen at ambient temperature over 35 minutes to a stirred solution of 6,7-dihydrobenzo[b]thiophen-4(5H)-one (4.6 g) in tetrahydrofuran (45 ml), the mixture was stirred for 1 hour and allowed to stand at ambient temperature overnight, then it was filtered and the solvent was removed in vacuo. The residue was dissolved in dimethylformamide (20 ml), the solution was added under nitrogen to a suspension of lithium carbonate (8.2 g) in dimethylformamide (50 ml), the mixture was heated under reflux for 4 hours, then it was cooled to ambient temperature and added to 10% aqueous acetic acid solution (500 ml). The product was extracted into dichloromethane (3×100 ml) and the combined extracts were washed with water (3×100 ml), dried (MgSO4), and the solvent was removed in vacuo. The residue was purified by flash chromatography over silica using dichloromethane as eluant. Appropriate fractions were combined and the solvents removed in vacuo to give benzo[b]thiophen-4-ol (4 g) as a white solid which was used without further purification.

Provenance & Evidence