p-Toluenesulfonic acid → diethyl 4-oxo-4H-pyrano[2,3-b]pyridine-6,7-dicarboxylate
Reaction equation
CN(C)[CH:3]=[CH:4][C:5]([C:7]1[C:12](=[O:13])[NH:11][C:10]([C:14]([O:16][CH2:17][CH3:18])=[O:15])=[C:9]([C:19]([O:21][CH2:22][CH3:23])=[O:20])[CH:8]=1)=[O:6].C1(C)C=CC(S(O)(=O)=O)=CC=1>C(O)(=O)C>[O:6]=[C:5]1[C:7]2[C:12](=[N:11][C:10]([C:14]([O:16][CH2:17][CH3:18])=[O:15])=[C:9]([C:19]([O:21][CH2:22][CH3:23])=[O:20])[CH:8]=2)[O:13][CH:3]=[CH:4]1Participants
4
Procedure
Diethyl 5-[3-(dimethylamino)acryloyl]-1,6-dihydro-6-oxo-2,3-pyridinedicarboxylate (6 g, 0.0178 mol), and p-toluenesulfonic acid (4.5 g, 0.021 mol) in acetic acid (60 mL) are heated at reflux for three hours. The mixture is then evaporated to dryness, neutralized with a saturated NaHCO3 solution and extracted with methylene chloride. The organic solution is dried over Na2SO4, and concentrated to a thick oil, which solidifies after trituration with hexane-ether (4 g, 77%). The product is recrystallized from isopropanol to give a melting point 71°-72° C.