反应详情

A mixture of 60 parts of 3,4-dihydro-6-nitro-2H-1-benzopyran-2-carboxylic acid, 480 parts of ethanol and 5.52 parts of concentrate sulfuric acid was stirred for 2 hours at reflux temperature. The reaction mixture was evaporated. The residue was crystallized from 2,2'-oxybispropane (activated charcoal). The product was filtered off and dried, yielding 65 parts (95%) of ethyl 3,4-dihydro-6-nitro-2H-1-benzopyran-2-carboxylate; mp. 80.8° C. (intermediate 23).

1. temperatureat reflux temperature
2. customThe reaction mixture was evaporated
3. customThe residue was crystallized from 2,2'-oxybispropane (activated charcoal)
4. filtrationThe product was filtered off
5. customdried