[CH2:1]([O:8][CH2:9][C:10]([F:19])([F:18])[CH2:11][CH2:12]OS(C)(=O)=O)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[C:20]1(=[O:30])[NH:24][C:23](=[O:25])[C:22]2=[CH:26][CH:27]=[CH:28][CH:29]=[C:21]12.[K]>CN(C=O)C>[CH2:1]([O:8][CH2:9][C:10]([F:19])([F:18])[CH2:11][CH2:12][N:24]1[C:23](=[O:25])[C:22]2=[CH:26][CH:27]=[CH:28][CH:29]=[C:21]2[C:20]1=[O:30])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1A mixture of 1-benzyloxy-2,2-difluoro-4-methanesulfonyloxybutane (63.44 g, 0.216 moles), potassium phthalimide (44 g, 0.238 moles) and dry DMF (500 mL), distilled from CaH2) is stirred and heated at 100° C. After a short time the mixture solidifies, and an additional dry DMF (500 mL) is added. Upon heating at 90°-100° C. for another 20 hours, salts are removed by filtration, and the DMF is distilled under vacuum (oil pump). The residue is dissolved in CH2Cl2 (800 mL) and washed with 1N KOH (twice) and 1N HCl (twice). Drying (Na2SO4) and evaporation yields N-(4-benzyloxy-3,3-difluorobutyl)-phthalimide as a yellow oil: 68.5 g (92%).
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