The preparation method is obtained by removing two hydrogen atoms from 2-p-chlorophenyl-1-methyl-5-trifluoromethyl-2-pyrroline -3-nitrile.
2.3g(0.011mol) of bromine was added to carbon tetrachloride solution containing 3.2g(0.01mol)2-p-chlorophenyl -1-methyl -5-trifluoromethyl pyrrole -3-nitrile, and stirred at room temperature for 1.5h,. Then heat to 70 ℃ for 2.5h and cool to room temperature. Dilute with water, extract with ethyl acetate for 3 times, wash the extract with water once, wash with sodium metabisulfite aqueous solution for 2 times, and then wash with water once, dry with anhydrous magnesium sulfate, filter, vacuum Dissolve to obtain a brown-yellow solid product, and then recrystallize with a mixed solvent of n-heptane and ethyl acetate to obtain 2-p-chlorophenyl -1-methyl -5, 83% yield.