Preparation method of 4,5-dihydroxyl-2-methyl benzoic acid

The invention discloses a preparation method of 4,5-dihydroxyl-2-methyl benzoic acid and belongs to the fields of fine chemical engineering and medicine intermediates. The preparation method of 4,5-dihydroxyl-2-methyl benzoic acid comprises the following steps: preparing an intermediate III or V by taking 4-methylbenze-1,2-diphenol as a raw material, then preparing an intermediate IV by virtue of the intermediate III or V, then transforming the intermediate IV into an intermediate II, and finally preparing 4,5-dihydroxyl-2-methyl benzoic acid by virtue of the intermediate II. The preparation method of 4,5-dihydroxyl-2-methyl benzoic acid has the advantage that the problems that raw materials are difficult to acquire, byproducts are many, yield is low, cost is high, steps are miscellaneous, safety can not be guaranteed and serious pollution is produced in the prior art are overcome.