反应详情

To a suspension of 2-carboxymethyl-5-methyl-benzoic acid (2.544 g, 13.1 mmol) in anhydrous dichloromethane (70 ml) held at 0° C. was added tert-butyl 2,2,2-trichloroacetimidate (11.47 mg, 52.4 mmol, 2 equivalents) in cyclohexane (85 ml). BBr3 (0.52 ml) was then added, and the reaction mixture was raised to room temperature and stirred for 16 hr. Solid NaHCO3 was added to quench the reaction, the solid precipitate was filtered off and washed with ether. The combined organic washing was evaporated to dryness, and the residue obtained was purified by silica gel chromatography to obtain 2-tert-butoxycarbonylmethyl-5-methyl benzoic acid tert-butyl ester 3.345 g (83.3%) as an oil. 1H NMR (CDCl3): 7.718 (1H, s), 7.227 (1H, d, J=7.57 Hz), 3.910 (2H, s), 2.362 (3H, s), 1.584 (9H, s), 1.443 (9H, s). FABMS (+Ve) m/z 307 [MH+], 251 [MH+—C4H8], 195 [MH30 —2C4H4]. Anal. calcd. for C18H26O4: C, 70.6; H, 8.6. Found: C, 70.82; H, 8.53.

1. customheld at 0° C.
2. customto quench
3. customthe reaction
4. filtrationthe solid precipitate was filtered off
5. washwashed with ether
6. washThe combined organic washing
7. customwas evaporated to dryness
8. customthe residue obtained
9. customwas purified by silica gel chromatography