反应详情

30 Parts of 3,4-dihydro-2H-1-benzopyran-2-carboxylic acid were added slowly, during a 30 minutes-period, to 79 parts of a solution of nitric acid 60% while cooling on an ice bath. The whole was stirred for 10 minutes at room temperature. The reaction mixture was poured onto ice water. The product was extracted with trichloromethane. The extract was dried, filtered and evaporated. The residue was purified by column chromatography over silica gel using a mixture of trichloromethane and methanol (90:10 by volume) as eluent. The pure fractions were collected and the eluent was evaporated. The residue was crystallized from a mixture of ethanol and water (80:20 by volume), yielding 17 parts (45%) of 3,4-dihydro-6-nitro-2H-1-benzopyran-2-carboxylic acid; mp. 180° C. (intermediate 22).

1. additionThe reaction mixture was poured onto ice water
2. extractionThe product was extracted with trichloromethane
3. customThe extract was dried
4. filtrationfiltered
5. customevaporated
6. customThe residue was purified by column chromatography over silica gel using
7. additiona mixture of trichloromethane and methanol (90:10 by volume) as eluent
8. customThe pure fractions were collected
9. customthe eluent was evaporated
10. customThe residue was crystallized from a mixture of ethanol and water (80:20 by volume)