Preparation method of imidocarb

The invention relates to a preparation method of imidocarb. The preparation method of the imidocarb comprises the following steps: (1) mixing nitrobenzoic acid with thionyl chloride and obtaining nitrobenzoyl chloride by carrying out a reflux reaction of the nitrobenzoic acid and the thionyl chloride, (2) adding the nitrobenzoyl chloride into acetonitrile and then adding P-Mo-V heteropolyacid and ethylenediamine, obtaining 2-(3-nitrophenyl) imidazoline by carrying out the reflux reaction of the nitrobenzoyl chloride, acetonitrile, the P-Mo-V heteropolyacid and the ethylenediamine (3) adding the 2-(3-nitrophenyl) imidazoline into a solvent, adding palladium carbon, and obtaining 2-(3-nitrophenyl) imidazoline hydrochloride by carrying out a reduction hydrogenation reaction of the 2-(3-nitrophenyl) imidazoline, the solvent and the palladium carbon, (4) adding the 2-(3-nitrophenyl) imidazoline hydrochloride into N-dimethylformamide, stirring and adding urea, and obtaining the imidocarb by carrying out a reaction of the 2-(3-nitrophenyl) imidazoline hydrochloride, N-dimethylformamide and urea for 4.5-5.5 hours. According to the method, purity of imidocarb liquid is more than 99%, and molar yield is stabilized at more than 71% and higher than the existing highest yield of 65%.