Patent ID: 7932415

Claim:
A process for manufacturing E-N,N-diethyl-2-cyano-3-(3,4 -dihydroxy-5-nitrophenyl) acrylamide, comprising: a) reacting 3,4-dihydroxy-5-nitrobenzaldehyde with N,N-diethyl-2 -cyanoacetamide in the presence of a catalyst in a C4 to C8 alcohol at reduced pressure and at a temperature of at least 70° C.; b) optionally cooling the resulting mixture from step a); c) optionally seeding the resulting mixture from step a) or step b) with N,N-diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide comprising at least 60% of the E-isomer by weight in the seeding crystals; d) cooling the mixture from step a) or step b) or step c) to a temperature of 30° C. or below; e) seeding the cooled mixture from step d) with N,N-diethyl-2-cyano-3 -(3,4-dihydroxy-5-nitrophenyl)acrylamide comprising at least 10% of the Z-isomer by weight in the seeding crystals; f) cooling the mixture from step e) to a temperature of 5° c or below; g) isolating the crystallized product from the mixture; and h) converting the obtained mixture of the E- and Z-isomers of N, N-diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide to the E-isomer of N, N-diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide.