Simple preparation method of thioether dianhydride

The invention discloses a simple preparation method of thioether dianhydride of following structual formula, wherein the substituted position of sulfur on the phenyl ring can be 3,3' position, 4,4' position, or 3,4' position. The method comprises the following steps: using 3-chlorophthalic anhydride or/and 4-chlorophthalic anhydride as a raw material, mixing the raw material with the equimolar quantity of aniline in a mixed solvent composed of polar aprotic solvents and benzene solvents to combine the anhydride end group protection with coupling reaction process to complete the two processes in a first pot to obtain corresponding N,N'-disubstituted thioether imide, and then combining a process of acidifying after hydrolysis deprotection to obtain thioether tetracid with a process of dehydrating thioether tetracid to obtain thioether dianhydride to complete the two processes in a second pot, so as to obtain thioether dianhydride. Compared with a four-step reaction used in the prior art, the method of the invention has the advantages of simpleness, short flow, low cost, little three wastes (waste gas, waste water and industrial residue), and recyclable partial raw materials and solvents, and is a green preparation method with low cost.