[OH:1][C:2]1[CH:9]=[CH:8][C:7]([O:10][CH3:11])=[CH:6][C:3]=1[CH:4]=[O:5].[C:12](=O)([O-])[O-].[Cs+].[Cs+].C1(C)C(S(O[CH2:28][CH2:29][O:30][S:31]([C:34]2[C:35](C)=[CH:36][CH:37]=[CH:38][CH:39]=2)(=[O:33])=[O:32])(=O)=O)=CC=CC=1>CN(C=O)C>[CH3:11][O:10][C:7]1[CH:8]=[CH:9][C:2]([O:1][CH2:28][CH2:29][O:30][S:31]([C:34]2[CH:39]=[CH:38][C:37]([CH3:12])=[CH:36][CH:35]=2)(=[O:32])=[O:33])=[C:3]([CH:6]=1)[CH:4]=[O:5]To a vigorously stirred solution of 15,2 g (100 mmol) 2-hydroxy-5-methoxy-benzaldehyde and 42.4 g (130 mmol) caesium carbonate in 350 ml DMF at 0° C. was added 46.3 g (125 mmol) ethylene glycol bis-toluene sulfonate (Aldrich) in 50 ml DMF dropwisely. The reaction mixture was stirred vigorously at 70° C. for 5 h. The solvent was evaporated. 200 ml water and 200 ml ethyl acetate were added. The organic phase was separated. The aqueous phase was extracted three times with 100 ml ethyl acetate each. The combined organic phases were washed with 50 ml water and 50 ml brine. The organic phase was dried with magnesium sulfate and evaporated. The crude product was purified by silica column chromatography (gradient ethylacetate:hexane 1:6, ethyl acetate→1:2). The desired product 5a was obtained in 75% yield (26.3 g, 75 mmol) as yellow oil.
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