[CH3:1][O:2][C:3](=[O:21])[CH:4](I)[CH2:5][CH2:6][N:7]1[CH:11]=[CH:10][CH:9]=[C:8]1[C:12](=[O:19])[C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1.OO.CCCCCC.C(OCC)(=O)C>CS(C)=O.O.O.O.O.O.O.O.S([O-])([O-])(=O)=O.[Fe+2].S([O-])([O-])(=O)=O.[Fe+2].O>[CH3:1][O:2][C:3]([CH:4]1[C:11]2=[CH:10][CH:9]=[C:8]([C:12]([C:13]3[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=3)=[O:19])[N:7]2[CH2:6][CH2:5]1)=[O:21]4-(2-Benzoylpyrrol-1-yl)-2-iodobutyric acid methyl ester (IV, 3.17 grams, 8 mmol) was dissolved in dimethylsulfoxide (32 mL). Iron (II) sulfate heptahydrate (230 mg, 0.827 mmol) was added, and the mixture was stirred for 5 minutes. Hydrogen peroxide (30% aqueous solution, 6 mL) was added dropwise while the internal temperature of the reaction was kept below 35° C. by application of an external water bath. After 45 minutes, TLC (4:1 hexane:ethyl acetate, silica) indicated the reaction was about 60% complete. Additional hydrogen peroxide (2 mL) was added. After 20 minutes more, an additional 2 mL of peroxide and 70 mg of iron sulfate were added) and 15 minutes later, an additional 0.5 mL of peroxide. 20 Minutes after the final peroxide addition, the mixture was poured into water (200 mL). The resulting mixture was extracted with ether (50 mL), then saturated with sodium chloride and extracted twice more with ether. The combined organic extracts were washed twice with water (50 mL each), then once with brine (25 mL), dried over magnesium sulfate, and evaporated in vacuo to afford ketorolac methyl ester (2.095 g, still containing traces of ether (1%) and DMSO (<0.3%) by NMR. Yield calculated on the basis of weight and NMR purity is 96%. The product may be crystallized from methanol, m.p. 80°-82° C.
Loading…
