Accessing Polycyclic Heteroarenes Enabled by Copper-Catalyzed Aerobic Oxidative C–H/C–H [4 + 2] Annulation of 3-Arylindole Derivatives

Abstract

Several polycyclic aromatic hydrocarbons are delivered at room temperature by copper-catalyzed aerobic oxidative C−H/C−H [4 + 2] annulation of alkyl-substituted 3-arylindole derivatives. Specifically, dual aryl C−H functionalization is furnished under mild conditions through the 1,2-migration of copper catalyst and regioselective alkyne insertion. Mechanistic experiments demonstrate that the C−H bond cleavage on the indole and phenyl rings is not involved in the rate-limiting step.

Copper-catalyzed oxidative dehydrogenative dearomatization of indole derivatives: A new strategy to construct spirocyclic indolenines

“…Among these reactions, copper has been recognized as an effective catalyst for oxidative coupling and aerobic oxidation to construct C-C bonds and C-O bonds as a cheap and abundant transition metal catalyst. 52 , 53 , 54 , 55 , 56 In our efforts to develop copper-catalyzed oxidative annulation and aerobic oxidation transformations, 57 , 58 , 59 , 60 , 61 we recognized that copper catalysts showed excellent activity in introducing different groups into heterocyclic compounds. Combining these two concepts, we envisioned that copper-catalyzed oxidative annulation furnished the dearomatization of indole derivatives to generate spiroindolenines containing fluorene and indeno[2,1- b ]indole groups ( Scheme 1 d).…”

Synthesis of N-Fused Polycyclic Indole Derivatives via Ru(II)-Catalyzed C–H Bond Activation and Intramolecular Hydroarylation

“…For instance, Diels–Alder reactions have been known as a general way to access N -fused tetracyclic scaffolds. , Photocatalytic intramolecular coupling reactions and radical-based cascade approaches have also been well developed to synthesize polycyclic indole derivatives. Transition metal-catalyzed cyclization, intramolecular annulation/amination, oxidative coupling, and C–H functionalization are recently developed strategies to synthesize N -fused polycyclic indoles. During the past few decades, transition metal-catalyzed C–H functionalization has been explored as an increasingly major effective tool for building organic molecules with synthetic efficiency .…”

Access to Azepino-Annulated Benzo[c]carbazoles Enabled by Gold-Catalyzed Hydroarylation of Alkynylindoles and Subsequent Oxidative Cyclization

“…Within carbazole chemistry, there are interesting polycyclic frameworks called benzo­[ c ]­carbazoles. To date, many methodologies have been established to construct these molecules, including Pd­(II)-catalyzed C–H activation, − photochemical cyclization, Diels–Alder reaction of 2-alkenylindoles with arynes, , Brønsted acid mediated cycloaromatization, annulation of azide-diynes with arenes, and other methods. − Despite these significant contributions on the construction of benzo­[ c ]­carbazole skeletons as well as piperidine-annulated ones (Scheme a), ,, much less attention has been focused toward the construction of azepino-annulated ones, presumably due to their unfavorable transannular interactions and entropic effection for the synthesis of a seven-membered ring . To the best of our knowledge, there are only two examples reported by Zhang and co-workers in 2011 through photoinduced cyclization of highly functionalized indoles bearing a remote alkyne or alkene from N1 connection (Scheme b), which, however, suffers from preorganized indole cores and narrow substrates scope.…”

“…To the best of our knowledge, there are only two examples reported by Zhang and co-workers in 2011 through photoinduced cyclization of highly functionalized indoles bearing a remote alkyne or alkene from N1 connection (Scheme b), which, however, suffers from preorganized indole cores and narrow substrates scope. Very recently, Yue, Liu and co-workers reported a Cu­(II)-catalyzed polycyclization strategy to construct piperidine-annulated benzo­[ c ]­carbazoles . This method, unfortunately, could not be extended to a larger ring.…”