反应详情

3,5-Dimethylnitrobenzene (30 g, 0.198 M) was heated with stirring to 80° in a mixture of pyridine (400 ml) and water (250 ml). KMnO4 (62.7 g, 0.396 M) was added in portions over 0.75 hours, and heating continued at 85-90° for 1.75 hours. The hot solution was filtered through celite, washing with hot water (150 ml). The pink filtrates were decolourised with a few drops of sodium metabisulfite, and evaporated to dryness. The residue was dissolved in water (250 ml), and extracted with diethyl ether (2×90 ml). The aqueous layer was acidified (concentrated hydrochloric acid), and extracted with ethyl acetate (3×120 ml). Combined organic extracts were washed with NaH2PO4 solution, brine, and dried over MgSO4. Crude product was eluted through a pad of silica, using a mixture of ethyl acetate/dichloromethane/acetic acid (25:25:1), to give 3-methyl-5-nitrobenzoic acid (14.5 g, 40%), mp 171-172°. Nmr (DMSO-d6): δ 2.51 (s, 3H); 8.17 (s, 1H); 8.30 (t, 1H); 8.42 (t, 1H); 13.58 (br, 1H).

1. temperatureheating
2. filtrationThe hot solution was filtered through celite
3. washwashing with hot water (150 ml)
4. customevaporated to dryness
5. dissolutionThe residue was dissolved in water (250 ml)
6. extractionextracted with diethyl ether (2×90 ml)
7. extractionextracted with ethyl acetate (3×120 ml)
8. washCombined organic extracts were washed with NaH2PO4 solution, brine
9. dry with materialdried over MgSO4
10. washCrude product was eluted through a pad of silica
11. additiona mixture of ethyl acetate/dichloromethane/acetic acid (25:25:1)