C([O:4][C@H:5]1[CH:9]=[CH:8][C@@H:7]([OH:10])[CH2:6]1)(=O)C.N1C=CN=C1.[Si:16](Cl)([C:19]([CH3:22])([CH3:21])[CH3:20])([CH3:18])[CH3:17].C(=O)([O-])[O-].[K+].[K+]>O1CCCC1>[C:19]([Si:16]([CH3:18])([CH3:17])[O:4][C@H:5]1[CH2:6][C@@H:7]([OH:10])[CH:8]=[CH:9]1)([CH3:22])([CH3:21])[CH3:20]To a solution of (1R,3S)-(+)-4-cyclopentene-1,3-diol 1-acetate (1.0 g, 7.03 mmol) (Aldrich) and imidazole (960 mg, 14.06 mmol) (Aldrich) in tetrahydrofuran (35 mL) was added tert-butyldimethylsilyl chloride (1.27 g, 8.44 mmol) (Aldrich). The mixture was allowed to warm slowly to room temperature, stirred overnight and then partitioned between ethyl acetate and water. The organic layer was collected, dried over sodium sulfate, filtered and concentrated to a residue that was dissolved in methanol (45 mL). To this solution was added potassium carbonate (1.17 g, 8.44 mmol) and the mixture stirred overnight. The next morning the reaction mixture was partitioned between ethyl acetate and water. The organic layer was collected, dried over sodium sulfate, filtered and concentrated to a residue that was purified by silica gel column chromatography with a 0–30% diethyl ether in hexanes gradient to give (−)-(1R,4S)-4-(tert-butyl-dimethyl-silanyloxy)-cyclopent-2-enol as a colorless oil. (Yield 1.29 g, 85%).
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