[O:1]1[CH2:5][CH2:4][O:3][CH:2]1[C:6]1[CH:7]=[CH:8][C:9]2[O:13][CH:12]=[CH:11][C:10]=2[CH:14]=1.C([Li])CCC.C1C=CC(S(N(S(C2C=CC=CC=2)(=O)=O)[F:30])(=O)=O)=CC=1.O>C1COCC1.C(OCC)(=O)C>[F:30][C:12]1[O:13][C:9]2[CH:8]=[CH:7][C:6]([CH:2]3[O:3][CH2:4][CH2:5][O:1]3)=[CH:14][C:10]=2[CH:11]=15-[1,3]Dioxolan-2-yl-benzofuran (50 mg, 0.26 mmol) was dissolved in THF (2 mL) and the solution was cooled down to −78° C. Butyl lithium (180 uL, 1.1 eq.) was added dropwise. This mixture was stirred 30 min at 25° C. Then the reaction mixture was cooled down to −78° C. and N-fluorodibenzenesulfonamide (91 mg, 1.1 eq.), dissolved in 1 mL THF, was added dropwise to the reaction mixture. The mixture was stirred overnight between −78° C. and room temperature. Water and ethyl acetate were added to the mixture and the aqueous layer was extracted 3 times. Combined organic phases was dried over MgSO4, filtrated and evaporated, to give the 2-Fluoro-5-[1,3]dioxolan-2-yl-benzofuran (75 mg) mixed with side products. However it was sufficiently pure to be used for the next step.
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