Palladium‐Catalyzed Ring‐Expansion Reaction of Indoles with Alkynes: From Indoles to Tetrahydroquinoline Derivatives Under Mild Reaction Conditions

Abstract

Ausbaufähiges Indol: Die hoch selektiv mit O2 als Oxidationsmittel und unter doppelter C‐H‐Aktivierung verlaufende Titelreaktion öffnet einen neuen Zugang zu polysubstituierten 4,5‐Dihydrocyclopenta[c]chinolinen (siehe Schema). Außerdem wurden Einblicke in den Mechanismus dieser Ringerweiterung erhalten.

Palladium‐Catalyzed Oxidative Carbocyclizations

“…Later, Jiao and co-workers found that treatment of indoles 63 with disubstitued ethynes in the presence of Pd-A C H T U N G T R E N N U N G (OAc) 2 in CH 3 CN/AcOH under O 2 atmosphere exclusively afforded polysubstituted 4,5-dihydroquinolines 64 (Scheme 73) without formation of carbazoles, [74] which is totally different from the results obtained in Scheme 72. It is worth noting that this ring-expansion reaction involves a dual CÀH bond activation, one CÀC bond cleavage, and five new C À C bond formations.…”