[CH3:1][C:2]1[N:7]=[C:6]([C:8]([C:10]2[CH:15]=[CH:14][C:13]([O:16][CH3:17])=[C:12]([O:18][CH3:19])[CH:11]=2)=[O:9])[CH:5]=[CH:4][CH:3]=1.C1(C)C=CC(S(O)(=O)=O)=CC=1.[CH2:31](O)[CH2:32][CH2:33][OH:34].C(=O)(O)[O-].[Na+]>C1(C)C=CC=CC=1.O>[CH3:19][O:18][C:12]1[CH:11]=[C:10]([C:8]2([C:6]3[CH:5]=[CH:4][CH:3]=[C:2]([CH3:1])[N:7]=3)[O:34][CH2:33][CH2:32][CH2:31][O:9]2)[CH:15]=[CH:14][C:13]=1[O:16][CH3:17]About 77.1 g. of (3,4-dimethoxyphenyl) (6-methyl-2-pyridyl) ketone, 74.1 g. of p-toluenesulfonic acid and 22.8 ml of 1,3-propanediol in 600 ml of toluene were heated under reflux with stirring for 17 hours. The water evolved during the reaction was neutralized with 500 ml of saturated sodium bicarbonate. Two phases formed and the phases were separated. The organic layer was washed with saturated sodium bicarbonate solution and dried over magnesium sulfate. Removal of the desiccant and solvent gave a solid residue which, on recrystallization from a mixture of acetone and petroleum ether (b.p. 60°-80°C.), yielded 2-(3,4-dimethoxyphenyl)-2-(6-methyl-2-pyridyl)-1,3-dioxane, m.p. 124°-126°C.
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