O[C:2]1[CH:3]=[CH:4][C:5]2[S:9][CH2:8][CH2:7][C:6]=2[CH:10]=1.[C:11](O)([CH3:14])([CH3:13])[CH3:12].OS(O)(=O)=O>C1C=CC=CC=1.O>[C:11]([C:3]1[CH:2]=[CH:10][C:6]2[CH2:7][CH2:8][S:9][C:5]=2[CH:4]=1)([CH3:14])([CH3:13])[CH3:12]To a solution of 5-hydroxy-2,3-dihydrobenzothiophene (500 mg, 3.28 mmoles) in 20 mL benzene in a sealable tube was added t-butanol (729 mg, 9.84 mmoles, 3.0 eq) and 0.4 mL concentrated H2SO4. The tube was sealed and the reaction mixture heated at 60° C. for 24 hours. The reaction mixture was cooled, diluted with water (50 mL) and extracted 2×25 mL ether. The combined extracts were washed with sodium bicarbonate (1×25 mL), H2O (1×25 mL) and brine (1×25 mL). The organic layer was then dried over Na2SO4, filtered and concentrated to give 220 mg crude product. Purification by flash chromatography (90/10, hexane/EtOAc) afforded 125 mg pure product (18%) mp 90°-93° C.
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