Dimethylformamide → 2-Amino-4-ethoxy-5-formylthiophene-3-carbonitrile

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Reaction Steps

168 parts of 2-amino-3-cyano-4-ethoxythiophene (Example 1) are dissolved in 500 parts of dimethylformamide, and 200 parts of phosphoryl trichloride are added dropwise to the stirred solution. The reaction is exothermic, and the rate of dropwise addition is adjusted so that the temperature of the reaction mixture does not exceed 50° C. Stirring is continued for 4 hours at 50° C., 50 parts of ice are added, and the mixture is stirred until a clear solution has formed. This solution is run into 2000 parts of 12.5% strength sodium hydroxide solution and the temperature is kept at 20°-30° C. Stirring is continued for 8 hours at room temperature, after which the product is filtered off under suction, washed with water and dried. 185 parts of 2-amino-3-cyano-4-ethoxy-5-formylthiophene are obtained. A sample recrystallized from pentanol melts at 245°-246° C. and has the following analytical values:

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