反应详情

温度

78 °C

2.50 g of 4-methoxy-2,3-dimethylbenzoic acid (G1) are dissolved in 160 ml of tetrahydrofuran under a nitrogen atmosphere and cooled to (−) 78° C. 11.5 ml of sec-BuLi are subsequently added dropwise at such a rate that the temperature of the reaction solution does not exceed (−) 65° C. When the addition is complete, the reddish reaction solution is stirred for a further 30 min with cooling. 3.59 ml of methyl iodide are then slowly added drop-wise. The cooling is subsequently removed, and the mixture is stirred for 1 h. For work-up, 160 ml of water are carefully added. The solution is subsequently extracted twice with 130 ml of ethyl acetate each time. The aqueous phase is cooled in an ice bath with stirring, acidified using 1.0 M HCl and filtered after 30 min. The filter cake is rinsed with cold water and subsequently recrystallised from 2-propanol. The crystals are filtered off with suction and dried for 2 h at 70° C. in vacuo, giving 1.90 g of the title compound as a colourless, crystalline solid having a melting point of 176.7° C.; MS: 194.2 (M+); TLC: Rf=0.29 (diethyl ether/petroleum ether 1:1 parts by volume).

1. custom65° C
2. additionWhen the addition
3. temperaturewith cooling
4. customThe cooling is subsequently removed
5. stirringthe mixture is stirred for 1 h
6. additionFor work-up, 160 ml of water are carefully added
7. extractionThe solution is subsequently extracted twice with 130 ml of ethyl acetate each time
8. temperatureThe aqueous phase is cooled in an ice bath
9. stirringwith stirring
10. filtrationfiltered after 30 min
11. washThe filter cake is rinsed with cold water
12. customsubsequently recrystallised from 2-propanol
13. filtrationThe crystals are filtered off with suction
14. customdried for 2 h at 70° C. in vacuo