Preparation method of synthetic 5-substituted-2-thiophenic acid

The invention relates to a preparation method of synthetic 5-substituted-2-thiophenic acid. The preparation method specifically comprises the following steps of using 2-halothiophene shown in formula 1 as the raw material, using a zeolite molecular sieve as a catalyst, using trichloro-acetic chloride as an acylating agent, uniformly mixing under the condition of non solvent or organic solvent, and reacting for 15 to 72h at the temperature of 60 to 130 DEG C, so as to obtain a compound (2) shown in formula 2; adding an alkaline solution into the compound (2) shown in formula 2, uniformly stirring, and hydrolyzing for 3 to 4h at the temperature of 70 to 100 DEG C, so as to obtain a target compound (3) shown in formula 3. The preparation method has the advantages that the cost of raw material is low, the obtaining is easy, the operation is simple and convenient, the operation cost is low, and the green and environment-friendly effects are realized; the yield rate in each reaction step is higher than the yield rate of the existing synthesis route, and the preparation method is suitable for the industrialized production; the industrial application value is stronger.