Hydrochloric Acid → 3-(2',4'-Difluoro-4-biphenylyl)-2-butenoic acid ethyl ester

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Reaction Steps

20.5 g. of 4-amino-2',4'-difluorobiphenyl are dissolved in a mixture of 25 ml. of 35% hydrochloric acid, 50 ml. of acetic acid and 120 ml. of water. The solution is cooled to 0° and 6.0 g. of NaNO2 are added in portions. Subsequently, a solution of 1.5 g. of Cu2Cl2, 0.9 g. of LiCl and 100 g. of crotonic acid ethyl ester in 900 ml. of acetone is added dropwise at -10° to the stirred mixture under a N2 atmosphere. The mixture is stirred for 4 hours more at 0°-5° and for 14 hours at 20° and extracted with benzene. The extract is washed and evaporated to give 20 g. of crude 2-chloro-3-(2',4'-difluoro-4-biphenylyl)-2-butenoic acid ethyl ester. This is dissolved in 250 ml. of acetic acid to which 50 g. of zinc dust are added. The mixture is stirred for 3 hours at 20° and filtered. After the customary work up, 3-(2',4'-difluoro-4-biphenylyl)-2-butenoic acid ethyl ester, m.p. 54°-56°, is obtained from the filtrate.

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