Photosensitization of organogold intermediates is an emerging field in catalysis. In this context, an access to 2,3-disubstituted indoles from o-alkynyl aniline and iodoalkyne derivatives via a gold-catalyzed sequence under visible-light irradiation and in the absence of an exogenous photocatalyst was uncovered. A wide scope of the process is observed. Of note, 2-iodo-ynamides can be used as electrophiles in this cross-coupling reaction. The resulting N-alkynyl indoles lend themselves to post-functionalization affording valuable scaffolds, notably benzo[a]carbazoles. Mechanistic studies converge on the fact that a potassium sulfonyl amide generates emissive aggregates in the reaction medium. Static quenching of these aggregates by a vinylgold(I) intermediate yields to an excited state of the latter, which can react with an electrophile via oxidative addition and reductive elimination to forge the key C-C bond. This reactant-induced photoactivation of an organogold intermediate opens rich perspectives in the field of cross-coupling reactions.

A pathway for the synthesis of 3-sulfonylindoles has been devised. Upon blue LED irradiation, in the presence of a gold­(I) or a silver­(I) salt, ortho-alkynyl N-sulfonyl precursors readily undergo a 5-endo-dig cyclization concomitant with a 1,3-sulfonyl migration. While the gold-catalyzed reaction takes place in photocatalyst-free conditions, an iridium photocatalyst (Ir­[dF­(CF3)­ppy]2(dtbbpy)­PF6) is necessary with silver catalysis. Mechanistic studies featuring the generation of a sulfonyl radical support this dichotomy.