A method for synthesizing
mesalazine is disclosed. The method comprises the following steps: 1) adding p-
nitrophenol, p-toluenesulfonic acid, absolute ethyl
alcohol and
hexamethylenetetramine, stopping heating after the reaction is finished, heating to
room temperature while stirring with
ice water, separating out solids, filtering, washing and
drying to obtain 5-nitrosalicylaldehyde; 2) adding the 5-nitrosalicylaldehyde,
potassium tert-butoxide,
copper salt and
acetonitrile, adding tert-butyl hydroperoxide while stirring, after the reaction is finished, performing vacuum concentration to remove the
solvent, pouring cold water into residues, stirring, performing suction
filtration, adjusting the pH value of the filtrate with
hydrochloric acid, performing suction
filtration, and
drying to obtain 5-nitrosalicylic acid; and 3) adding
stannous chloride dihydrate, concentrated
hydrochloric acid, the 5-nitrosalicylic acid and
ethanol, carrying out vacuum concentration after the reaction is finished, dissolving residues in water, adjusting the pH value with a concentrated
hydrochloric acid solution, standing for
crystallization, carrying out suction
filtration, washing
filter cake with water, and
drying to obtain
mesalazine. No isomer is generated, and the yield is high; the method does not need high-temperature and high-pressure conditions; the reaction cost is low; and raw materialsand auxiliary materials with high
toxicity and heavy environmental
pollution are not used.