反应详情

The preparation of 2-amino-4-chloro-3-cyano-5-formylthiophene is known from EP-A-No. 193 885, according to which the intermediate triethylamine salt of 3-chloro-1,1-dicyano-2-hydroxy-1-propene is prepared from malononitrile, chloroacetyl chloride, and triethylamine and cyclized with ammonium sulfide to 2-amino-3-cyano-4-hydroxythiophene, which is then treated with a mixture of N,N-dimethylformamide and phosphoryl chloride; the N'-(4-chloro-3-cyano-5-formyl-2-thienyl)-N,N-dimethylformamidine that is formed is isolated and then hydrolyzed with formic acid, giving the required product. However, it has been found that the yield of 2-amino-4-chloro-3-cyano-5-formylthiophene obtained by this process is unsatisfactory.