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In Dean-Stark apparatus, a mixture of 37 g (190.5 mmol) of 2-phenylbutanedioic acid, 6 mL of conc. H2SO4, 80 mL of toluene and 80 mL of EtOH is refluxed for 72 hours. After cooling to room temperature, the reaction mixture is concentrated under reduced pressure and then treated with 300 mL of water, and extracted with Et2O (2×400 mL). The organic phases are combined, dried over Na2SO4, filtered and then concentrated under reduced pressure. The residue obtained is purified by chromatography on a column of silica gel, eluting with a cyclohexane/EtOAc gradient of 0 to 10% EtOAc. 22 g of diethyl 2-phenylbutanedioate are obtained in the form of an oil.

1. temperatureis refluxed for 72 hours
2. concentrationthe reaction mixture is concentrated under reduced pressure
3. additiontreated with 300 mL of water
4. extractionextracted with Et2O (2×400 mL)
5. dry with materialdried over Na2SO4
6. filtrationfiltered
7. concentrationconcentrated under reduced pressure
8. customThe residue obtained
9. customis purified by chromatography on a column of silica gel
10. washeluting with a cyclohexane/EtOAc gradient of 0 to 10% EtOAc