High-purity isothiocyanate compound preparation method for industrial production

A process for the preparation of an isothiocyanate compound of formula (I),

• A-N═C═S (I)
• in formula I:
• —N═C═S is isothiocyanate group;
• A is —XR1 or —CR2R3R4, wherein
• X is —(CH2)n—, and n is an integer of 0-6;
• R1 is selected from the group consisting of methyl, tert-butyl, isopropyl, methylthio, methoxy, allyl, methallyl, cyclohexyl, methylsulfinyl, naphthyl, methyl cyclohexyl, morpholinyl, diethylamino, benzoyl, ethoxycarbonyl, tert-octyl, chlorine, trimethylsilyl, substituted or unsubstituted phenyl;
• wherein, the “substituted” means that one or more hydrogen in the group are substituted by substituents selected from the following group:
• halogen, methyl, bromomethyl, ethyl, methoxy, nitro, azido, trifluoromethyl, difluoromethoxy, methylthio, cyano, trifluoromethoxy, trifluoromethylthio, tert-butoxycarbonyl, ethoxycarbonyl;
• R2, R3, and R4 are each independently H, phenyl or C1-3 alkyl;
• wherein the process comprises the following steps:
• A-NH2dithiocarbamateA-N═C═S (I)
• (1) in the presence of an organic base, ANH2 reacts with CS2 in organic solvent to obtain a first reaction mixture containing dithiocarbamate;
• (2) in the presence of an optional base catalyst, adding desulfurizing agent to the first reaction mixture to carry out a desulfurization reaction so as to obtain a second reaction mixture containing isothiocyanate compound;
• (3) the second reaction mixture is purified by post-processing to obtain the isothiocyanate as shown in formula (I).