反应详情

To a mechanically stirred solution of ethyl 4-aminobenzoate (165 g, 1 mol) in THF (1.2 L) and pyridine (200 mL) at ˜10° C. was added portionwise (˜10–20 g each time) of pyridine hydrobromide perbromide (tech. 90%, 365 g, 1.02 mol) over a period of 1 h. Internal temperature was kept at 10–15° C. After completion of addition, the mixture was stirred for 30 min, then filtered through celite and the filter cake was washed with THF (1 L). The filtrate was diluted with Et2O, washed with 0.5 M of aqueous NaHSO3 (2×, 400 mL), brine, dried (MgSO4) and concentrated. The residue contained too much H2O and therefore was dissolved in EtOAc (1 L), washed with brine, dried (MgSO4) and concentrated to give a semi-solid residue. The residue was swished with hexanes-Et2O (2:1) to yield 187 g (77%) of the title compound as a white powder. The mother liquor was evaporated and swished again to give 19 g (8%) of additional title compound as a light brown powder.

1. customwas kept at 10–15° C
2. additionAfter completion of addition
3. filtrationfiltered through celite
4. washthe filter cake was washed with THF (1 L)
5. additionThe filtrate was diluted with Et2O
6. washwashed with 0.5 M of aqueous NaHSO3 (2×, 400 mL), brine
7. dry with materialdried (MgSO4)
8. concentrationconcentrated
9. dissolutionwas dissolved in EtOAc (1 L)
10. washwashed with brine
11. dry with materialdried (MgSO4)
12. concentrationconcentrated
13. customto give a semi-solid residue