p-Toluenesulfonic acid → Ethyl 2-[4-(2-oxothiolan-3-ylidenemethyl)phenyl]propionate
Reaction equation
O[CH:2]([CH:16]1[CH2:20][CH2:19][S:18][C:17]1=[O:21])[C:3]1[CH:8]=[CH:7][C:6]([CH:9]([CH3:15])[C:10]([O:12][CH2:13][CH3:14])=[O:11])=[CH:5][CH:4]=1.C1(C)C=CC(S(O)(=O)=O)=CC=1>C1(C)C=CC=CC=1>[O:21]=[C:17]1[C:16](=[CH:2][C:3]2[CH:8]=[CH:7][C:6]([CH:9]([CH3:15])[C:10]([O:12][CH2:13][CH3:14])=[O:11])=[CH:5][CH:4]=2)[CH2:20][CH2:19][S:18]1Participants
4
Procedure
Ethyl 2-{4-[hydroxy(2-oxothiolan-3-yl)methyl]phenyl}propionate (300 mg) obtained in Example 32 was dissolved in toluene (3.0 ml), and to the solution was added p-toluenesulfonic acid (200 mg), and stirred for 1 hour under reflux by heating. The solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (hexane/ethyl acetate=5/1) to give the title compound (251 mg, 89%).