Transition-metal-free and organic solvent-free conversion of N-substituted 2-aminobiaryls into corresponding carbazoles via intramolecular oxidative radical cyclization induced by peroxodisulfate

Abstract

An atom-economical and environmentally benign synthesis of N-substituted carbazoles is described. This methodology afforded products in 90–120 minutes.

Facial Syntheses of Bromobenzothiazines via Catalyst-Free Tandem C–H Amination/Bromination in Water

“…To overcome these drawbacks, a green bromination reaction has been developed using inorganic bromine salts and peroxides, where the key step in these reactions is the generation of “Br + ” . Recently, Natarajan’s group and Muñiz’s group almost simultaneously achieved intramolecular C–H amination using n Bu 4 NBr and peroxides. Obviously, the combination of inorganic bromine salts and peroxides is effective for both the intramolecular C–N bond formation and aromatic C–H bromination.…”

Oxidative Radical-Mediated Addition of Ethers to Quinone Imine Ketals: An Access to Hemiaminals

“…On the basis of literature reports, control experiments, and the EPR study, we believe that the reaction mechanism proceeds via the radical pathway. The reaction starts with homolytic cleavage of persulfate under thermal conditions in the presence of tetrabutylammonium chloride to form the sulfate radical anion as shown in Scheme . The formed sulfate radical anion abstracts the proton from the α-position to oxygen of ether and generates α-oxyalkyl radical A as a reactive intermediate.…”

Iodine(III)-Enabled Distal C–H Functionalization of Biarylsulfonanilides

“…The current work is encompassed toward organic transformations involving nitrenium ion intermediate by controlling the reactivity toward distal C–H functionalization . However, the prevalent intramolecular C–H amination techniques for synthesis of carbazoles are centered on proximal C–H bond functionalization (Figure b). , Abundance of carbazole scaffolds in numerous pharmaceutical agents and natural products have drawn significant attention of synthetic chemists to develop efficient methods for carbazole synthesis. Intramolecular oxidative C­(sp 2 )–H amination is one of the most followed synthetic protocols toward three-ring N -heterocycle carbazole synthesis. , Nishiyama used hypervalent iodine­(III) reagent to synthesize carbazoles using an anodic oxidation technique. , Buchwald and co-workers developed a Pd-catalyzed C–H amination protocol aided by Cu­(OAc) 2 as co-oxidant. , Later, Gaunt and Chang independently established Pd-catalyzed and Cu-catalyzed (or Cu-free) approaches, respectively, with the replacement of the metal oxidant by organic oxidant phenyliodine diacetate (PIDA) or phenyliodinetrifluoroacetate (PIFA).…”

“…41 However, the prevalent intramolecular C− H amination techniques for synthesis of carbazoles are centered on proximal C−H bond functionalization (Figure 2b). 42,43 Abundance of carbazole scaffolds in numerous pharmaceutical agents and natural products have drawn significant attention of synthetic chemists to develop efficient methods for carbazole synthesis. Intramolecular oxidative C(sp 2 )−H amination is one of the most followed synthetic protocols toward three-ring N-heterocycle carbazole synthesis.…”