反应详情

A mixture of 3.32 parts of 6,8-di-t-butyl-2,3-dihydro-4-oxo-4H-1-benzopyran-2-carboxylic acid, ethyl ester and 9.9 parts of lead tetraccetate was refluxed in 30 parts of glacial acetic acid for 6.5 hours. A further 9.9 parts of lead tetracetate were added and the reflux was continued for another 3.25 hours. After cooling, the reaction mixture was extracted with ether. The ether extract was washed with sodium bicarbonate solution and water and was dried. Evaporation of the ether gave an oil which was chromotographed on silica gel using a 9:1 mixture of toluene and ethanol for elution. This yielded 0.23 parts of 6,8-di-t-butyl-4-oxo-4H-1-benzopyran-2-carboxylic acid, ethyl ester, m.p. 130°-131.5° C (after crystallisation from light petroleum (b.p. 40°-60° C). This product was shown by spectral means to be the same as that of Example 13.

1. temperatureAfter cooling
2. extractionthe reaction mixture was extracted with ether
3. extractionThe ether extract
4. washwas washed with sodium bicarbonate solution and water
5. customwas dried
6. customEvaporation of the ether
7. customgave an oil which
8. washfor elution