Method for synthesizing diclofenac sodium

A method for synthesizing diclofenac sodium, comprising:

• (S1) subjecting aniline and chloroacetic acid to amidation in an organic solvent in the presence of a boric acid catalyst to obtain 2-chloro-N-phenylacetamide (II);
• (S2) subjecting 2-chloro-N-phenylacetamide (II) and 2,6-dichlorophenol to condensation reaction in the presence of potassium carbonate and a phase transfer catalyst to obtain 2-(2,6-dichlorophenoxy)-N-phenylacetamide (III);
• (S3) subjecting 2-(2,6-dichlorophenoxy)-N-phenylacetamide (III) to Smiles rearrangement in the presence of a basic catalyst to obtain N-(2,6-dichlorophenyl)-2-hydroxy-N-phenylacetamide (IV);
• (S4) subjecting N-(2,6-dichlorophenyl)-2-hydroxy-N-phenylacetamide (IV) and thionyl chloride to chlorination in the presence of a catalyst to obtain N-(2,6-dichlorophenyl)-2-chloro-N-phenylacetamide (V);
• (S5) subjecting N-(2,6-dichlorophenyl)-2-chloro-N-phenylacetamide (V) to Friedel-Crafts alkylation in the presence of a Lewis acid catalyst to obtain 1-(2,6-dichlorophenyl)-1,3-dihydro-2H-indol-2-one (VI);
• and
• (S6) subjecting 1-(2,6-dichlorophenyl)-1,3-dihydro-2H-indol-2-one (VI) to hydrolysis in the presence of an inorganic base to obtain diclofenac sodium (I).