Au- and In-Catalyzed Synthesis of 3- and 6-Sulfonylindoles

Significance

Unusual Au- and In-catalyzed reactions of ortho-alkynyl-N-sulfonylanilines to give the corresponding 3- and 6-sulfonylindoles are reported. In the Au-catalyzed process, the 3-sulfonylindoles are formed by a nucleophilic nitrogen-induced cyclization followed by an interesting intramolecular sulfonyl migration to the 3-position. In suprising contrast, the In-catalyzed reaction proceeds by an unprecedented 1,7-sulfonyl migration to produce the 6-sulfonylindoles as major product in good yields, together with minor 3-sulfonyl byproducts. Ir-arylsulfonyl complexation is suggested to play a crucial role in the selective production of 6-sulfonylindoles. Crossover experiments suggest the operation of an intramolecular migration pathway. Substrates with arylsulfonyl moieties bearing EDGs afforded products with higher regioselectivity.