FC(F)(C(F)F)COC1C=CC(C=O)=CC=1.C(CC(O)=O)#N.N1CCCCC1.[F:29][C:30]([F:46])([CH:43]([F:45])[F:44])[CH2:31][O:32][C:33]1[CH:42]=[CH:41][C:36](/[CH:37]=[CH:38]\[C:39]#[N:40])=[CH:35][CH:34]=1.FC(F)(C(F)F)COC1C=CC(/C=C/C#N)=CC=1>N1C=CC=CC=1>[F:29][C:30]([F:46])([CH:43]([F:44])[F:45])[CH2:31][O:32][C:33]1[CH:42]=[CH:41][C:36]([CH:37]=[CH:38][C:39]#[N:40])=[CH:35][CH:34]=1A mixture of 500 g of 4-(2,2,3,3-tetrafluoropropoxy)benzaldehyde, 183 g of cyanoacetic acid, 250 ml of pyridine and 250 ml of piperidine are heated with stirring and allowed to react for 1 hour at 110° C. A further 36.6 g of cyanoacetic acid are then added and the mixture is allowed to react for a further 30 minutes at 110° C. The reaction mixture is cooled, distilled under reduced pressure and 433.1 g of 4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile are obtained (yield: 78%; purity 95%) in the form of a mixture of isomers which contains cis-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile and trans-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile in a molar ratio cis:trans of approximately 1.35 to 1.8:1 (corresponding to a weight ratio of about (58 to 64):(42 to 36)) and in addition up to about 3% by weight of piperidine and 2% by weight of unidentified impurities and resins.
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