[O:1]1[CH:6]=[CH:5][CH2:4][CH2:3][CH2:2]1.C1(C)C=CC(S(O)(=O)=O)=CC=1.[CH3:18][O:19][C:20]1[N:25]=[CH:24][C:23]([OH:26])=[CH:22][CH:21]=1.O.ClCCl>ClCCl>[CH3:18][O:19][C:20]1[CH:21]=[CH:22][C:23]([O:26][CH:6]2[CH2:5][CH2:4][CH2:3][CH2:2][O:1]2)=[CH:24][N:25]=110.1 g (119.9 mmol, 1.5 eq.) of 3,4-dihydro-2H-pyran and 1.4 g (8.0 mmol, 0.1 eq.) of 4-toluenesulphonic acid were added to a solution of 10.0 g (79.9 mmol) of 6-methoxypyridin-3-ol in 150 ml of dichloromethane, and the mixture was stirred at RT for 5 d. After addition of water/dichloromethane and phase separation, the aqueous phase was extracted with dichloromethane. The combined organic phases were dried (sodium sulphate), filtered and concentrated under reduced pressure. Yield: 17.3 g (100% of theory)
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