Br[C:2]1(Br)[CH2:4][C:3]1(Br)[CH2:5][CH2:6][O:7][S:8]([C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1)(=[O:10])=[O:9].C[Li].O>C(OCC)C>[C:11]1([S:8]([O:7][CH2:6][CH2:5][C:3]2[CH2:4][CH:2]=2)(=[O:10])=[O:9])[CH:12]=[CH:13][CH:14]=[CH:15][CH:16]=1A solution of 0.745 g (0.00150 mol) of 1,1,2-tribromo-2-(2-benzenesulfonyloxyethyl)-cyclopropane in 4 ml of diethyl ether was placed under a nitrogen atmosphere by use of a Firestone valve. While cooling to −78° C. in a dry ice/acetone bath, 23.45 ml (0.00450 mol) of 1.4 M methyl lithium in diethyl ether was added slowly via syringe. After 15 minutes warmed to 0° C. in an ice water bath then returned to −78° C. for about 30 minutes before 2 ml of water was added via syringe. The resulting mixture was transferred to a separatory funnel and the phases were separated. The organic layer was dried over MgSO4 and filtered. The solvent was removed from the filtrate in vacuo with a bath temperature under 20° C. to yield >0.155 g of 70% pure 2-(2-benzenesulfonyloxyethyl)-cyclopropene contaminated with 30% 1-(2-hydroxethyl)cyclopropene as an oil.
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