Metal-free regioselective bromination of imidazo-heteroarenes: the dual role of an organic bromide salt in electrocatalysis

Abstract

This electrochemical protocol demonstrates an organic bromide salt i.e., tetra-n-butylammonium bromide (TBAB) as a brominating agent as well as an electrolyte for the regioselective bromination of several imidazo heteroaromatic motifs....

Recent progress in the oxidative bromination of arenes and heteroarenes

“…Roy's group 19 reported an electrochemical bromination by demonstrating the dual role of an organic bromide salt (tetra- n -butylammonium bromide, TBAB) as a brominating agent and as an electrolyte for the regioselective bromination of several imidazo-heteroaromatic molecules (Scheme 10). Mechanistic investigation revealed that this electrochemical bromination proceeded through the formation of molecular bromine by the anodic oxidation of bromide ions.…”

Photocatalytic cross-dehydrogenative coupling reaction toward the synthesis of N,N-disubstituted hydrazides and their bromides

“…Then, isomerization of intermediate 85 produces intermediate 86 , which reacts with BrCCl 3 to afford intermediate 87 in the presence of TBAB through this photoredox catalysis. 44 Next, deprotonation of 87 gives compound 82 . Subsequently, compound 82 is oxidized by Ir( iv ) to afford the cation radical intermediate 88 by a SET process, which is further transformed into radical 89 .…”

Synthesis of C‐3‐Functionalized Imidazo[1,2‐a]pyridines via Direct para‐Position Arylation of Electron‐Rich Anilines under Transition‐Metal‐Free Conditions

“…(Scheme 1c). [12] Inspired by these studies, we herein design a one-pot reaction using 2-bromo-1phenylethan-1-one, 2-aminopyridine and N,N-dimethylaniline.…”

“…Inspired by this work, several solvents such as MeCN, THF, dioxane, toluene, MeOH, DMF, DMSO, and H 2 O were evaluated; DMSO was found to be the best solvent (Table 1, entries 2-9). Based on these results, the effect of the reaction time was evaluated, and the desired product 4 a was obtained in 75% yield by prolonging the reaction time to 24 h. However, when the reaction time was increased to 48 h, the yield decreased slightly (Table 1, entries [10][11][12][13][14]. Temperature is also an important factor for the synthesis of the desired compounds.…”