反应详情

210 parts of 2-acetylamino-3-cyano-4-ethoxythiophene (Example 7) are introduced into 1000 parts of dimethylformamide, and 200 parts of phosphoryl trichloride are added dropwise in the course of 4 hours. Stirring is continued for 4 hours at 60° C., after which the resulting crystal slurry is brought into solution by adding 600 parts of ice. This solution is stirred into 2000 parts of 12.5% strength sodium hydroxide solution, and acidified with hydrochloric acid after 6 hours. The precipitated product is filtered off under suction, washed with water and dried to give 201 parts of 2-acetylamino-3-cyano-4-ethoxy-5-formylthiophene. A sample recrystallized from dimethylformamide has a melting point of 276°-277° C. and possesses the following analytical values:

1. additionare added dropwise in the course of 4 hours
2. additionby adding 600 parts of ice
3. filtrationThe precipitated product is filtered off under suction
4. washwashed with water
5. customdried