An alternative method for the regio- and stereoselective bromination of alkenes, alkynes, toluene derivatives and ketones using a bromide/bromate couple

Abstract

Mixtures of NaBr and NaBrO 3 in two different ratios have been used for highly stereoselective bromination of alkenes and alkynes, and regioselective bromine substitution at the a-carbon of ketones and at the benzylic position of toluene derivatives. The reactions were conducted in an aqueous acidic medium under ambient conditions. The solid reagents were prepared from the intermediate obtained in the ''cold process'' of bromine manufacture and are stable, nonhazardous and inexpensive to prepare. This procedure provides an efficient and practical alternative to conventional procedures using liquid bromine directly or indirectly.

Magnetic‐Nanoparticle‐Supported 2,2′‐Bis[3‐(triethoxysilyl)propyl]imidazolium‐Substituted Diethyl Ether Bis(tribromide): A Convenient Recyclable Reagent for Bromination

“…1 4 OH solution (25 %, 50 mL) was then added dropwise to the stirred mixture at room temperature to reach a reaction pH of 11. The resulting black dispersion was continuously stirred for 1 h at room temperature and then heated at reflux for 1 h to yield a brown dispersion.…”

“…A possible solution would be the development of a solid green reagent by utilizing the liquid bromine precursor of bromine manufacture. [4,5] Another is the application of recyclable reagents with byproducts that can be efficiently separated from reaction mixtures and reused. For example, to dress the recovery issue, many highly efficient strategies have been used to immobilize the reagent onto various supports such as organic polymers (Figure 1, ad), [6][7][8][9] silica sol-gel ( Figure 1, e), [10] and ionic liquids (Figure 1, f).…”

Synthesis and Fluorescence Properties of Novel indol-3yl-thiazolo[3,2-a][1,3,5]triazines and indole-3-carbaldehyde Schiff Bases

“…Preparation of α-bromoarylethanones and 2-amino-4-substituted phenyl-1,3-thiazole derivatives is shown in Scheme 1. To minimize the use of the hazardous brominating agents, potassium bromide-potassium bromate mixture was used for the regioselective bromination of acetophenones [18]. And, we found that the rate of bromination of acetophenone, p-chloro, p-fluoro, p-methoxyand o-hydroxyacetophenones were faster.…”

“…Synthesis of 2-amino-4-substituted phenyl-1,3-thiazoles (1b-7b) α-Bromoarylethanones (deliquescent) were prepared according to the reported method [18]. The ethanolic mixture of α-bromoarylethanone (1a, 1 mmol) and thiourea in the boiling tube was ultrasonicated at 45°C in an ultrasonic bath.…”

Solvent-Free Dibrominations of Alkenes and -Unsaturated Carbonyl Compounds using Cetyltrimethyl Ammonium Tribromide

“…Moreover, bromo compounds are important as intermediates in synthesis of organometallic compounds, in transition metal coupling reactions and as intermediates in various other organic transformations [4][5][6] . In this regard the quaternary ammonium tribromides (QATB) have become quite popular as reagents [7][8][9][10][11][12][13][14][15] .…”