反应详情

10.0 g of 2-ethyl-4-methoxy-3-methylbenzoic acid (F1) are suspended in 50 ml of dichloromethane under a nitrogen atmosphere. 29.3 ml of boron tribromide are subsequently slowly added dropwise with cooling in an ice bath. The transparent, red solution obtained is stirred at room temperature for 1 h. The mixture is subsequently carefully poured with stirring into 600 ml of ice-water. The aqueous phase is stirred for 30 min and subsequently extracted twice with 200 ml of ethyl acetate each time. The combined organic phases are washed once with 200 ml of water, dried over Na2SO4, evaporated in vacuo and purified by flash column chromatography on silica gel (solvent gradient: cyclohexane/0-100% by vol. of ethyl acetate), giving 9.37 g of the title compound as a colourless, amorphous solid having a melting point of 139° C.; MS: 180.0 (M+); TLC: Rf=0.33 (cyclohexane/methyl tert-butyl ether 3:2 parts by volume).

1. temperaturewith cooling in an ice bath
2. customThe transparent, red solution obtained
3. additionThe mixture is subsequently carefully poured
4. stirringThe aqueous phase is stirred for 30 min
5. extractionsubsequently extracted twice with 200 ml of ethyl acetate each time
6. washThe combined organic phases are washed once with 200 ml of water
7. dry with materialdried over Na2SO4
8. customevaporated in vacuo
9. custompurified by flash column chromatography on silica gel (solvent gradient: cyclohexane/0-100% by vol. of ethyl acetate)