O[CH2:2][CH2:3][C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=1[CH2:10][CH2:11][O:12]S(C)(=O)=O.[H-].[Na+].[H][H]>O1CCCC1>[CH:6]1[C:5]2[CH2:10][CH2:11][O:12][CH2:2][CH2:3][C:4]=2[CH:9]=[CH:8][CH:7]=1.[CH2:2]=[CH:3][C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1Methanesulfonic acid 2-[2-(2-hydroxy-ethyl)-phenyl]-ethyl ester (2.2 g/9.0 mmol) was dissolved in tetrahydrofuran (400 mL). Sodium hydride (540 mg/14.5 mmol) was added (hydrogen evolution) and the reaction allowed to stir at room temperature overnight. The reaction was quenched by the addition of water (10 mL) and the reaction concentrated to a volume of ca. 50 mL by rotary evaporation. The residue was partitioned between water (50 mL) and ethyl ether (50 mL). The aqueous layer was extracted with an additional portion of ethyl ether (50 mL) and the combined organics were washed with brine (100 mL), dried over magnesium sulfate, filtered and concentrated onto silica gel. Column chromatography on silica gel (eluting with 0→50% ethyl acetate/hexanes) afforded 5,6,8,9-Tetrahydro-7-oxa-benzocycloheptene as a colorless oil (240 mg/18%) along with a styrene by-product formed by mesylate elimination (600 mg/45%). Oxapene: 1H NMR (400 MHz, CDCl3) δ 7.11 (m, 4H), 3.80 (m, 4H), 3.00 (m, 4H).
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