Beneficial effect of carboxylic acid additives on the Pd-catalyzed intramolecular N-arylation of 2-amino-3-(2-chlorophenylsulfonyl)pyrroles

Carboxylic acid additives have been shown to significantly improve the yield of the Pd-catalyzed intramolecular N-arylation of 2-aminopyrroles containing a 2-chlorophenylsulfonyl group at the 3-position to give a novel tricyclic ring system. Pivalic and phenylacetic acid provided the best yield enhancement, while acetic acid showed moderate enhancement. Other acids showed limited to no enhancement or even a detrimental effect on the reaction.