O

ch2-c-oh n ch3

According to the other scheme, phenylhydrazone (3.2.46) undergoes cyclization in the presence of the same p-chlorobenzoic acid chloride, during which acylation of hydrazone and its cyclization into methyl ester of 5-methoxy-2-methyl-2-(p-chlorobenzoyl)-3-indoly-lacetic acid (3.2.52) simultaneously take place. The resulting product is further hydrolyzed by an alkali to give indomethacin (3.2.51) [113,114].

Cl Cl

The same substance has been suggested to be synthesized directly from 4-methoxyphenyl-n-chlorobenzoylhydrazine and levulinic acid by cyclization of the respective hydrazone in the presence of hydrogen chloride. In order to do this, condensation of acetaldehyde with n-methoxyphenylhyrazine gives hydrazone (3.2.53), which is acylated by p-chlorobenzoyl chloride, forming hydrazone (3.2.54). The product is hydrolyzed into hydrazine (3.2.55). Interacting the product with levulinic acid gives hydrazone (3.2.56), which undergoes Fischer cyclization into indomethacin (3.2.51) [115].

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