The invention discloses a preparation method of tralopyril, and particularly relates to the technical field of
agriculture. The preparation method provided by the invention comprises the steps of 1, dissolving p-chlorobenzonitrile in
acetonitrile, and carrying out a salt forming reaction under the
catalysis of an
organic base to obtain an
alkali metal salt (I) of p-chlorophenyl amino
acrylonitrile; 2, dissolving 1, 1, 1-trichloroacetone in
alkyl chloride, carrying out a one-step bromination reaction with
bromine, and carrying out extraction and
distillation to obtain 1-bromo-3, 3, 3-trifluoroacetone (II); 3, dissolving the intermediate I in
alkane, carrying out a ring closing reaction with the intermediate II through
acid catalysis to obtain a 2-(4-chlorphenyl)-5-(
trifluoromethyl)-1H-
pyrrole-3-
nitrile crude product, and carrying out
distillation and recrystallization to obtain a pure product; and 4, performing two-step bromination on the intermediate III through
bromine to obtain tralopyril. According to the intermediate obtained by the preparation method disclosed by the invention, the final product tralopyril is low in
impurity content and high in product purity, the raw materials are simple and easy to obtain, the preparation process is simple, the
reaction conditions are mild, and the preparation method is economical and environment-friendly and meets the requirements of industrial
mass production.