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0 °C

Bromoethane (0.7 mL) was added to a mixture of 1,1-dimethylethyl 4-(3-hydroxyphenyl)-1-piperazinecarboxylate (Description 21, 500 mg, 1.8 mmol) and potassium carbonate (495 mg) in acetone (50 mL) and the mixture was heated under reflux for 13 h. The mixture was cooled, water (100 mL) was added and the mixture was extracted with ether (3×100 mL). The combined organic fractions were dried (MgSO4) and the solvent was evaporated under reduced pressure. The residue was purified by flash column chromatography on silica gel, eluting with hexane/EtOAc (95:5). The residue was dissolved in dichloromethane (14 mL), cooled to 0° C. and trifluoroacetic acid (9 mL) was added. The mixture was stirred at 0° C. for 1 h., then allowed to warm to room temperature and saturated aqueous sodium bicarbonate solution (40 mL) was added. The mixture was extracted with dichloromethane, the combined organic fractions were dried (MgSO4) and the solvent was evaporated under reduced pressure to give the title compound as a pale brown solid (210 mg, 46%). 1H NMR (250 MHz, CDCl3) δ1.43 (3H, t, J 7.6 Hz), 3.65-3.82 (8H, m), 3.98-4.13 (2H, m), 6.84-6.91 (2H, m), and 7.34-7.40 (1H, m).

1. temperaturethe mixture was heated
2. temperatureunder reflux for 13 h
3. temperatureThe mixture was cooled
4. extractionthe mixture was extracted with ether (3×100 mL)
5. dry with materialThe combined organic fractions were dried (MgSO4)
6. customthe solvent was evaporated under reduced pressure
7. customThe residue was purified by flash column chromatography on silica gel
8. washeluting with hexane/EtOAc (95:5)
9. dissolutionThe residue was dissolved in dichloromethane (14 mL)
10. additiontrifluoroacetic acid (9 mL) was added
11. temperatureto warm to room temperature
12. additionsaturated aqueous sodium bicarbonate solution (40 mL) was added
13. extractionThe mixture was extracted with dichloromethane
14. dry with materialthe combined organic fractions were dried (MgSO4)
15. customthe solvent was evaporated under reduced pressure