Acid‐Catalyzed Recyclization of Aroyl‐Containing Thieno[2,3‐ <i>b</i> ]Pyridin‐6( <scp> 5 <i>H</i> </scp> )‐Ones Into Substituted Thieno[2,3‐ <i>b</i> ]Pyrroles

ABSTRACT In the present communication a novel method for the synthesis of thieno[2,3‐ b ]pyrrole derivatives was developed. The considered approach is based on a previously undescribed recyclization of thieno[2,3‐ b ]pyridin‐6(5 H )‐ones bearing aroyl fragment under the action of p‐toluenesulfonic acid in alcoholic media. The elaborated general protocol allowed us to obtain a set of 22 target esters of (thieno[2,3‐ b ]pyrrol‐4‐yl)acetic acids with yields up to 84%. Readily accessible starting materials, mild reaction conditions, atom economy, and convenient isolation of the final products without chromatographic purification are the advantages of the presented procedure. The structure of one of the prepared thieno[2,3‐ b ]pyrroles was proved by X‐ray diffraction.