反应详情

A solution of crude 5-chloro-2-methyl-3-nitrobenzoic acid (13.2 g) in dry methanol (100 mL) was cooled to 0° C. (3 mL) was added conc. H2SO4 dropwise. After the addition, the mixture was heated to reflux for 16 hr. After removal of solvents under reduced pressure, the crude product was purified by silica gel chromatography (petroleum ether to petroleum ether/EtOAc=50:1) to give the title compound (6.3 g, yield 35% for two steps) as a white solid. LC-MS (ESI) m/z: 230 (M+1)+, 231 (M+2)+. 1H-NMR (400 MHz, CDCl3) δ (ppm): 2.59 (s, 3H), 3.95 (s, 3H), 7.84-7.85 (d, 1H), 7.98-7.99 (d, 1H).

1. additionAfter the addition
2. temperaturethe mixture was heated
3. temperatureto reflux for 16 hr
4. customAfter removal of solvents under reduced pressure
5. customthe crude product was purified by silica gel chromatography (petroleum ether to petroleum ether/EtOAc=50:1)