Oxidative Halogenation of Aromatic Compounds with Metal Halides and Sodium Bismuthate

Abstract

A new mild and efficient method for aromatic halogenation with a wide variety of halides in the presence of sodium bismuthate NaBO 3 in AcOH is reported. Metal halides of groups Ia, IIa, IIIa, IVa, Va, and the first row of transition elements are suitable for this method.There has been a growing interest in the last few years in metal halides as alternatives to molecular halogens in halogenations of aromatic compounds [1] [2]. Halides of transition metals of groups I, IV, and V have received particular attention [3 ± 6]. Generation of halogens from these metal halides requires very drastic conditions [7] [8]. Other methods involve oxidation of certain halides with hardly available and expensive oxidizing agents such as peroxyacetic acid [9], lead tetraacetate [10], and nitrogen dioxide [11].Bismuthate ion is a strong oxidizing agent, but little attention has been paid to its potential in organic synthesis [12]. It has long been known that the ion oxidizes halides to the corresponding halogen in aqueous HClO 4 [13] [14]. No studies have been carried out regarding the exploitation of the reagent in the halogenation of organic compounds with metal halides. XWe hereby wish to report a new method for aromatic chlorination and bromination with various halides in the presence of NaBiO 3 .Results and Discussion. ± Appropriate amounts of the aromatic substrate and the halide were allowed to react with NaBiO 3 in AcOH at room temperature. The reaction was monitored with a moist starch-iodide paper held over the reaction vessel. The blue color indicated the presence of free halogen in the reaction mixture.All metal halides of groups Ia, IIa, IIIa, IVa, Va, and the first row of transition metals react with NaBiO 3 in AcOH and produce the corresponding halogen. The reactivity of NaBiO 3 with halides varies from metal to metal. We found that the rate of halogen production increases as we go from the top of the group to the bottom. The reactivity is also affected by the amount of H 2 O present in the halide crystals. Anhydrous forms are more reactive than their hydrated forms.Naphthalene was chosen for a comparative study of aromatic chlorination and bromination with various metal chlorides and bromides. The results are summarized in Tables 1 and 2.

Molecular genetic evidence supporting the neoplastic nature of stromal cells in ‘fibrosis’ after chemotherapy for testicular germ cell tumours

“…The later trait was of special significance, since the reaction conditions involve both elevated temperatures (∼400 °C) and the partaking of a catalytically active species, opening up potential pathways to many undesired decomposition and condensation reactions. One such pathway of aromatic nitrile decomposition involves CH bond cleavage,14 but also the oxidative halogenation of the aromatic unit in the presence of a metal halide 15–17. Homolytic cleavage of the carbon nitrile bond at temperatures above 400 °C and the associated depletion of nitrogen content within the structure were observed previously for a set of studied model compounds in this type of reaction 13, 18…”

Rational Extension of the Family of Layered, Covalent, Triazine‐Based Frameworks with Regular Porosity

“…One such pathway of aromatic nitrile decomposition involves CÀH bond cleavage, [14] but also the oxidative halogenation of the aromatic unit in the presence of a metal halide. [15][16][17] Homolytic cleavage of the carbon nitrile bond at temperatures above 400 8C and the associated depletion of nitrogen content within the structure were observed previously for a set of studied model compounds in this type of reaction. [13,18] The framework CTF-2 was synthesized heating zinc chloride and 2,6-naphthalenedicarbonitrile in a quartz glass ampoule at 400 8C for 40 h. The set-up in a closed system was chosen since the monomer starts to sublimate at temperatures around 220 8C.…”

Ecofriendly Oxidative Nuclear Halogenation of Aromatic Compounds Using Potassium and Ammonium Halides

“…Some other reports are also available on oxidative bromination using titanium(IV) grafted MCM-48, 26 titanium phosphate, 27 and titanium-modified zirconium phosphate. 28 A method for the bromination of aromatic compounds was reported by Mauthen, 19 in which several metal bromides, including potassium bromide, were used as brominating agents and NaBiO 3 as an oxidant in acetic acid. Less-activated aromatic compounds afforded monobrominated products, whereas highly activated aromatics such as anilines and phenols afforded tribrominated products.…”