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

In this work, we studied the aluminum chloride catalyzed reaction of 1‐benzenesulfonyl‐1 H ‐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‐1 H ‐pyrrole‐3‐carbonyl chloride and 1‐methyl‐1 H ‐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‐1 H ‐pyrrole.