Method for ammonolyzing and synthesizing meloxicam under catalysis of Lewis acid

The invention relates to a method for ammonolyzing and synthesizing meloxicam under the catalysis of Lewis acid. Under the catalysis of silicate Lewis acid, the meloxicam is synthesized from 4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxylic acid ethyl ester 1,1-dioxide and 2-amino-5methylthiazol. Compared with the direct ammonolysis method, the method has the advantages that: (1) the reaction time is about 4 to 6 hours which is shortened by four times and ammonolysis is complete; and (2) the ammonolysis yield is high which is more than or equal to 85 percent; decomposers and carbides are avoided; the product is easy to purify; the method for synthesizing the meloxicam is suitable for mass production; the product purity reaches 99 percent through HPLC detection; the product is light yellow green; and the product quality meets Chinese pharmacopoeia 2005.