Synthetic method of salicylic acid compound

The invention discloses a method of selectively achieving hydroxylation at an o-position of an oriented group to synthesize a salicylic acid compound with low-cost copper as a catalyst under the effect of a N,O-bidentate oriented group. The method includes the following steps: (1) adding aromatic acylaminopyridine-1-oxide, basic cupric carbonate, potassium carbonate, water and DMPU successively into a reaction tube; (2) performing a reaction at 105-115 DEG C for 20-30 h; (3) performing extraction, concentration and chromatographic separation to obtain an o-position hydroxylated product; (3) dissolving the o-position hydroxylated product in an ethanol solution of NaOH, performing a reaction at 85-95 DEG C for 20-30 h; and (4) after the reaction is finished, adding diluted hydrochloric acid to neutralize residual NaOH, and performing extraction, concentration and column chromatography to obtain the salicylic acid compound. The method is mild in reaction conditions, is good in tolerance of functional groups, and can selectively achieve the hydroxylation of a C-H bond at the o-position with the oriented group being easily to remove. The raw materials are low in cost and are easy to obtain. The method is simple in operations and is high in yield and good in suitable range.