Pd-Catalyzed cascade cyclization of o-alkynylanilines via C–H/C–N bond cleavage leading to dibenzo[a,c]carbazoles

Abstract

A new and efficient Pd-catalyzed cascade cyclization of biaryl-tethered o-alkynylanilines for the formation of dibenzo[a,c]carbazole derivatives has been reported. The use of the alkyl-substituted tertiary anilines together with the combination of the PdCl2 catalyst with the MnO2 oxidant and PivOH is vital for giving rise to 5-endo cyclization, C-N bond cleavage, and C-H bond activation in a cascade manner to produce the corresponding products with structural diversity.

Rh(III)-Catalyzed Asymmetric Synthesis of Axially Chiral Biindolyls by Merging C–H Activation and Nucleophilic Cyclization

“…Despite the advances, asymmetric synthesis of biaryls is generally rare, and most studies relied on dynamic kinetic resolution of conformationally labile biaryls, , as in a notable report by Shi . Besides the C–H activation process, metal-aryls can also be accessed via nucleophilic cyclization of alkynes (Scheme a) . However, this important area almost evolved independently with intermolecular C–H activation. , …”

Pd-Catalyzed Indolization/peri-C–H Annulation/N-Dealkylation Cascade to Cyclopenta-Fused Acenaphtho[1,2-b]indole Scaffold

“…Recently, we and other groups have demonstrated that the Pd-catalyzed heteroannulation of the N,N-disubstituted o -alkynylanilines was an efficient approach for the synthesis of structurally diverse indole derivatives . The generated indolium-Pd intermediate is relatively stable to avoid the rapid protonation and is capable of undergoing subsequent coupling, amidation, and ortho -C­(sp 2 )–H activation reactions to form various indole-fused PHAs.…”

Copper(I)-Mediated Cascade Annulation via Dual C–H/C–H Activation: Access to Benzo[a]carbazolic AEEgens

“…Based on the mechanistic studies in Scheme , HRMS analysis of reaction aliquots (Figure S3), and earlier reports, a plausible mechanism for this transformation is proposed in Scheme . At first, in the presence of a silver salt, the transient silver–amine complex A is formed to prevent the transition metal poisoning from free −NH 2 of 1a .…”