Tandem Palladium/Copper-Catalyzed Decarboxylative Approach to Benzoimidazo- and Imidazophenanthridine Skeletons

Abstract

A protocol for a tandem Pd/Cu-catalyzed intermolecular cross-coupling cascade between o-bromobenzoic acids and 2-(2-bromoaryl)-1H-benzo[d]imidazoles or the corresponding imidazoles is presented. The protocol provides conceptually novel and controlled access to synthetically useful N-fused (benzo)imidazophenanthridine scaffolds with high efficiency, a broad substrate scope, and excellent functional group compatibility.

Palladium-catalyzed decarboxylation [2 + 2 + 2] annulation approach to chromone-containing polycyclic compounds

“…On the basis of relevant literatures [14][15][16] and our previous works, 12 a plausible mechanism for the construction of 4a via the palladium-catalyzed three-component domino annulation among 3-iodochromone (1a), norbornene (2a), and o-bromobenzoic acid (3a) was proposed in Scheme 7. Initially, CNP intermediate C was smoothly generated through successive oxidative addition of Pd(0) to 1a, migratory insertion of NBE and intramolecular ortho-C(sp 2 )-H activation.…”

“…Recently, decarboxylative cyclization reactions involved a carboxylic-assisted palladacycle capture strategy using o-bromobenzoic acids as coupling reagents have been developed by Kwong, 14 Yang, 15 and Wang. 16 In these reactions, the direct transformation of C(sp 2 )-Br and C(sp 2 )-COOH bonds into two new C-C bonds were found as the bond-forming mode. In view of these achievements in the palladium catalyzed domino annulations with o-bromobenzoic acids, [14][15][16] we envisioned that o-bromobenzoic acids could also be acted as electrophilic reagents to couple with the CNP through successive oxidative addition, reductive elimination, decarboxylation and reductive elimination process to give chromone-containing polycyclic compounds (Scheme 1D).…”

“…16 In these reactions, the direct transformation of C(sp 2 )-Br and C(sp 2 )-COOH bonds into two new C-C bonds were found as the bond-forming mode. In view of these achievements in the palladium catalyzed domino annulations with o-bromobenzoic acids, [14][15][16] we envisioned that o-bromobenzoic acids could also be acted as electrophilic reagents to couple with the CNP through successive oxidative addition, reductive elimination, decarboxylation and reductive elimination process to give chromone-containing polycyclic compounds (Scheme 1D). Herein, we will report our most recent endeavor on the palladium-catalyzed decarboxylation [2 + 2 + 2] annulation.…”

Copper-Catalyzed Consecutive Ullmann, Decarboxylation, Oxidation, and Dehydration Reaction for Synthesis of Pyrrolo or Pyrido[1,2-a]imidazo[1,2-c]quinazolines

“…Despite these considerable advances, there is still a need to develop synthetic methods for assembling such nitrogen-containing fused heterocyclic skeletons from basic chemicals in heterocyclic chemistry. As part of our continuous study on the synthesis of polycyclic fused heterocycles catalyzed by transition metal, the readily prepared 4,5-diaryl-2-(2-bromophenyl)-1 H -imidazole ( 1a ) was used to react with 2-bromobenzoic acid in the presence of palladium and a copper catalyst via a benzyne intermediate, resulting in the synthesis of heterocyclic compounds in our recent work . Unexpectedly, 4,5-diaryl-2-(2-bromophenyl)-1 H -imidazole could react with the ligand to give pyrrolo­[1,2- a ]­imidazo­[1,2- c ]­quinazoline without adding the reactant 2-bromobenzoic acid.…”

“…As part of our continuous study 11 on the synthesis of polycyclic fused heterocycles catalyzed by transition metal, the readily prepared 4,5-diaryl-2-(2-bromophenyl)-1H-imidazole (1a) was used to react with 2bromobenzoic acid in the presence of palladium and a copper catalyst via a benzyne intermediate, resulting in the synthesis of heterocyclic compounds in our recent work. 11…”