A study of the friedel‐crafts acylation of 1‐benzenesulfonyl‐1H‐pyrrole in the preparation of 3‐aroylpyrroles

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Abstract
In this work, we studied the aluminum chloride catalyzed reaction of 1‐benzenesulfonyl‐1H‐pyrrole with a series of eleven aroyl chlorides. The products formed were not isolated, but hydrolyzed to the target 3‐aroylpyrroles in overall yields, usually, higher than 50%. However, in the cases with the π electron rich 1‐phenyl‐1H‐pyrrole‐3‐carbonyl chloride and 1‐methyl‐1H‐indole‐3‐carbonyl chloride significant C‐2 substitution occured, resulting in the isolation of the corresponding 1‐benzenesulfonyl‐2‐aroylpyrroles as the predominant or the sole products. The desired C‐3 isomers were synthesized starting with 1‐triisopropylsilanyl‐1H‐pyrrole.