A new synthesis of some indolecarboxylic acids

1‐Substituted isatins are transformed into indole derivatives by means of ethyl chloroacetate. In fact, under the conditions of the Darzens reaction they give two glycidic ester isomers 4 and 5 which, by hydrolysis in alkaline medium, undergo a transposition to indole‐2,3‐dicarboxylic acids 2 together with minor amounts of indole‐3‐carboxylic acids 3 . From isatin itself, 2,3‐dicarboxyindole‐1‐acetic acid ( 6 ) was obtained.