Regioselective Oxybromination of Activated Aromatic Compounds Catalysed by Ammonium Molybdate+

Transition metal free, green and facile halogenation of ketene dithioacetals using a KX–oxidant system

A facile oxidative halogenation of α-oxo ketene dithioacetals is achieved by using a potassium halide and an oxidant combination under transition metal free conditions at ambient temperature.

The Oxidative Bromination and Iodination of Dimethylacetanilides

The oxidative bromination and iodination of the six dimethylacetanilides have been examined; whereas bromination of 2,4-dimethyl- and 2,6-dimethylacetanilides using potassium bromide, sodium tungstate and peracetic acid gave predominantly the 6- and 4-bromo compounds respectively, the 5- and 3-iodo compounds were obtained using hydrogen iodide and peracetic acid.

A New Ring Bromination Method for Aromatic Compounds under Solvent-Free Conditions with Nbs/Al2O3

Alumina supported N-bromosuccinimide was found to be an efficient reagent for ring bromination of a number of aromatic compounds under solvent-free conditions. In the absence of the alumina the reactions are slow and some of the substrates are recovered unchanged. Under the reaction conditions aromatic oximes are converted into the corresponding carbonyl compounds. The method is simple, safe and rapid.

Sodium sulfate–hydrogen peroxide–sodium chloride adduct: selective protocol for the oxidative bromination, iodination and temperature dependent oxidation of sulfides to sulfoxides and sulfones

Sodium sulfate–hydrogen peroxide–sodium chloride adduct: selective protocols for anilines and sulfides oxidation.

Green halogenation reactions for (hetero)aromatic ring systems in alcohol, water, or no solvent

A new method of brominating aromatic and heteroaromatic ring systems is investigated. The combination of hydrobromic acid as the halogen source, hydrogen peroxide as the oxidant, and ethanol, water, or no solvent are evaluated as greener conditions than those that have been previously published. The new conditions give high yields and good regioselectivity for a variety of substrates when the ring is activated by electron-donating groups or heteroatoms. Phenols, anisole, thiophenes, and pyrrole give comparable or superior results when compared to a traditional bromination by N-bromosuccinimide in tetrahydrofuran. Other nitrogen-containing heterocycles do not react under the conditions because they are protonated and hence deactivated; similarly, substrates with electron-withdrawing groups are not brominated. The reaction is very tolerant of a variety of functional groups.

A H2O2/HBr system – several directions but one choice: oxidation–bromination of secondary alcohols into mono- or dibromo ketones

Convenience of application, multifaceted reactivity, and compliance with green chemistry principles: H₂O₂–HBr(aq) system for preparation of bromo ketones with yields up to 91%.

Green halogenation of aromatic heterocycles using ammonium halide and hydrogen peroxide in acetic acid solvent

The green generation of X+ (X = Br, I) using hydrogen peroxide in aqueous acetic acid allows access to aromatic heterocyclic halides in yields and purities comparable to syntheses employing N-bromosuccinimide. In activated and unsubstituted thiophene rings, regioselectivity is quantitative for positions α to the sulfur; pyrroles also give quantitative reactions, at least initially. Deactivated rings, including furans and thiazoles, as well as thiophenes with strongly electron-withdrawing groups showed little to no reactivity under the conditions investigated. The reaction shows remarkable functional group tolerance (to alcohol, nitro, alkyl, halo, and carbonyl groups), as shown through reaction with substituted phenols. In all bromination reactions, reaction yields and regiochemistry were very similar to reactions involving N-bromosuccinimide in tetrahydrofuran solvent.

Synthesis of 5′-Bromo-2′-Hydroxy-4,4′,6′-TrimetHoxychalcone from Garcinia Nervosa and of its Isomer 3′-Bromo-2′-Hydroxy-4,4′,6′-Trimethoxychalcone

The unambiguous syntheses of the naturally occurring 5′-bromo-2′-hydroxy-4,4′,6′-trimethoxychalcone 1, a constituent of Garcinia nervosa, and its positional isomer 3′-bromo-2′-hydroxy-4,4′,6′-trimethoxychalcone 6 are described.

A novel synthesis of bromobenzenes using molecular bromine

Certain substituted bromobenzenes have been synthesized in acceptable yields using a novel Sandmeyer type reaction. The reactions are relatively quick and possibly proceed via a radical mechanism.