反应详情

温度

0 °C

To a solution of 4-(2-tert-butoxycarbonyl-ethyl)-3,5-dimethyl-benzoic acid methyl ester (10.8 g, 37.0 mmol) in ethanol (100 mL) a 2 M aq. solution of LiOH (50 mL) is added at 0° C. The turbid mixture is stirred at 0° C. for 30 min, then at rt for 4 h. The mixture is diluted with 10% aq. citric acid solution and extracted three times with diethyl ether. The combined org. extracts are dried over MgSO4, filtered and concentrated. The solid residue is suspended in diethyl ether/heptane, stirred at rt, and filtered. The slurry procedure in diethyl ether/heptane is repeated. The solid material is collected and dried under HV to give 4-(2-tert-butoxycarbonyl-ethyl)-3,5-dimethyl-benzoic acid (5.09 g) as a white crystalline powder; LC-MS: tR=0.95 min, [M+1]+=279.14; 1H NMR (CDCl3): δ 1.47 (s, 9H), 2.30-2.40 (m, 2H), 2.39 (s, 6H), 2.94-3.03 (m, 2H), 7.75 (s, 2H).

1. waitat rt for 4 h
2. extractionextracted three times with diethyl ether
3. dry with materialextracts are dried over MgSO4
4. filtrationfiltered
5. concentrationconcentrated
6. stirringstirred at rt
7. filtrationfiltered
8. customThe solid material is collected
9. customdried under HV