反应详情

A solution of the crude (±)-2-cyano-4-(2,5-diacetoxy-3,4,6-trimethylphenyl)butan-2-ol prepared in Example 60 in 2000 ml. of anhydrous methanol was cooled in a dry ice-ethanol bath. When the internal temperature reached -50°, HCl gas was passed rapidly into the solution. Over the next 45 minutes, the external and internal temperatures were allowed to come to -20° and +5°, respectively. These temperatures were maintained until the solution was saturated with HCl. The clear, dark brown solution was kept at +2° overnight, stripped of solvent at reduced pressure, diluted with 2000 ml. of H2O, heated at 40° under N2 for 2.0 hours, cooled and extracted with ethyl acetate and ether. The organic solutions were washed with saturated brine, dried over Na2SO4 and stripped of solvent to give (±)-methyl 4-(2,5-dihydroxy-3,4,6-trimethylphenyl)-2-hydroxy-2methylbutanoate as a dark green-black oil. TLC indicated that under these conditions, virtually no (±)-methyl 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylate had been formed.

1. customreached -50°
2. customOver the next 45 minutes
3. customto come to -20° and +5°
4. temperatureThese temperatures were maintained until the solution
5. additiondiluted with 2000 ml
6. temperaturecooled
7. extractionextracted with ethyl acetate and ether
8. washThe organic solutions were washed with saturated brine
9. dry with materialdried over Na2SO4