Bromo Compounds Research Articles

ChemInform Abstract: Trihaloisocyanuric Acid/Triphenylphosphine: An Efficient System for Regioselective Conversion of Epoxides into Vicinal Halohydrins and Vicinal Dihalides under Mild Conditions.

AbstractTribromoisocyanuric acid gives the corresponding bromo compounds in similar yields.

ChemInform Abstract: Use of Bromine and Bromo‐Organic Compounds in Organic Synthesis

AbstractReview: 2263 refs.

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.

2-Bromo-1-(1H-pyrazol-4-yl)ethanone: versatile precursors for novel mono-, bis- and poly{6-(1H-pyrazol-4-yl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines}

A simple synthesis of novel mono-, bis- and poly{6-(1H-pyrazol-4-yl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines} is reported. The formation of the target compounds was achieved by the reaction of 2-bromo-1-(5-methyl-1-phenyl-1H-pyrazol-4-yl)ethanone with the appropriate aminotriazolethiol or by the reaction of 6-pyrazolyl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine-3-thiol with the appropriate di- and poly(bromo) compounds. The structures of the newly synthesized compounds were established by spectroscopy and elemental analyses.

Photodegradation of methylene blue using magnetically reduced graphene oxide bismuth oxybromide composite

A magnetically reduced graphene oxide–bismuth oxybromide (MRGO–BiOBr) composite was successfully synthesized and found to possess magnetic, adsorptive and photocatalytic properties. The synthesized composite have been characterized by Fourier transform infrared spectroscopy (FT-IR), X-Ray Diffraction (X-RD), Scanning electron microscopy (SEM) and UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). Presence of FeO bond stretching vibrations and bromo compounds have been confirmed using FT-IR and the diffraction peaks of the composite obtained from X-RD showed a combination of peaks of both MRGO and BiOBr. SEM images further confirmed the presence of minute flakes of BiOBr scattered onto the surface of MRGO. Reduction in band gap energy from 2.76eV for pure BiOBr to 1.91eV for the composite was determined using UV–vis DRS. Photocatalytic degradation of Methylene Blue dye under visible light irradiation (150W Tungsten filament lamp) was examined using MRGO–BiOBr and around 96.84% of dye of 50ppm was degraded in 2h. Kinetic studies were done by splitting the kinetic data into 2 regions at 30min of irradiation and using the Langmuir–Hinshelwood (L–H) model to determine the rate constants. The composite was found to be easily separable in the presence of a magnet and on regeneration, studies showed no significant decrease in the photocatalytic activity of the composite even after 3 runs.

Assembling molecular Sierpiński triangle fractals.

Fractals, being "exactly the same at every scale or nearly the same at different scales" as defined by Benoit B. Mandelbrot, are complicated yet fascinating patterns that are important in aesthetics, mathematics, science and engineering. Extended molecular fractals formed by the self-assembly of small-molecule components have long been pursued but, to the best of our knowledge, not achieved. To tackle this challenge we designed and made two aromatic bromo compounds (4,4″-dibromo-1,1':3',1″-terphenyl and 4,4‴-dibromo-1,1':3',1″:4″,1‴-quaterphenyl) to serve as building blocks. The formation of synergistic halogen and hydrogen bonds between these molecules is the driving force to assemble successfully a whole series of defect-free molecular fractals, specifically Sierpiński triangles, on a Ag(111) surface below 80 K. Several critical points that govern the preparation of the molecular Sierpiński triangles were scrutinized experimentally and revealed explicitly. This new strategy may be applied to prepare and explore various planar molecular fractals at surfaces.

Selective Bromination of Pyrrole Derivatives, Carbazole and Aromatic Amines with DMSO/HBr under Mild Conditions

Bromination of pyrrole derivatives, carbazole and aromatic amines using the DMSO/HBr system affords high yields of the corresponding bromo compounds. Temperature control used in the bromination of anilines helped to promote selective formation of mono- or di-brominated products. Simple operation, low toxicity and high selectivity make this a promising new procedure for the bromination of aromatic compounds.

Evaluation of the biological activity of novel monocationic fluoroaryl-2,2'-bichalcophenes and their analogues.

A series of bichalcophene fluorobenzamidines 5a–e was synthesized from the corresponding mononitriles 4a–e via a direct reaction with lithium bis(trimethylsilyl)amide LiN(TMS)2 followed by de-protection with ethanolic HCl (gas). Bichalcophene fluorobenzonitriles 4a–e were prepared adopting a Stille coupling reaction between the bromo compounds 3a–c and 2-(tri-n-butylstannyl)furan or analogues. As an approach to drug discovery, the structure–antimutagenicity relationship of novel fluoroarylbichalcophenes was examined using the Ames Salmonella/microsomal assay. At nontoxic concentrations (10 and 20 μM), all derivatives alone or in combination with sodium azide (NaN3; 2 μg/plate) or benzo[a]pyrene (B[a]P; 20 μM) in the presence of S9 mix were not mutagenic. The fluoroaryl derivatives significantly reduced the NaN3-induced and B[a]P-induced mutagenicity under pre-exposure and co-exposure conditions. The recorded antimutagenic activity of fluoroaryl derivatives varied depending on the kind of mutagen and the exposure regimen. Monocationic fluoroarylbichalcophenes were superior to the corresponding mononitriles in reducing B[a]P-induced mutagenicity. Nevertheless, mononitriles were more active against NaN3, especially at low concentrations and under pre-exposure treatments. The antimutagenic activity was congruent with a high antioxidant activity that could promote the DNA repair system. The fluorine substitution changed the antimutagenic signature of bichalcophenes. Some of these compounds could be selected for further anticancer studies.

Synthetic and structural studies of piperidine carboxamide uranyl ion complexes

New piperidine based ligands of the type [C5H10NCONR2] (where R=CH3 (L1), C2H5 (L2) and iC3H7 (L3)) have been prepared and characterized. The complex chemistry of these ligands with uranyl chloride, bromide, nitrate and β-diketonates has been studied using IR and NMR spectroscopic methods. Crystal structures for the complexes [UO2Cl2(L3)2] (1), [UO2Br2(L3)2] (2) [UO2(NO3)2(L3)2] (5) and [UO2(C4H3SCOCHCOCF3)2(L3)] (8) have been determined by the X-ray diffraction method. The structures of 1 and 2 show that the uranyl ion is surrounded by two of the ligands and two halogen atoms in an octahedral geometry. The structure of 5 shows that the uranyl group is surrounded by two nitrate groups and two ligands in a hexagonal bipyramidal geometry. The structure of 8 shows that the uranyl group is surrounded by two β-diketonates and one ligand in a pentagonal bipyramidal geometry. The structures show that the carboxamide ligands are strongly bonded to the uranyl group, showing a near linear geometry for the U–O–C bond (angle 150–159°). The prepared chloro and bromo compounds are air and moisture stable and show good solubility in normal organic solvents.

Scalar Relaxation of the Second Kind. A Potential Source of Information on the Dynamics of Molecular Movements. 3. A 13C Nuclear Spin Relaxation Study of CBrX3 (X = Cl, CH3, Br) Molecules

Continuing studies based on measurements of the nuclear spin relaxation rates running via the SC2 mechanism (scalar relaxation of the second kind), we present in this work the results obtained for three bromo compounds: CBrCl3, (CH3)3CBr, and CBr4. A careful separation of saturation-recovery curves, measured for signals of (13)C nuclei at 7.05 and 11.7 T on two components, has provided the longitudinal SC2 relaxation rates of carbon signals in (79)Br and (81)Br containing isotopomers of the investigated compounds. These data have enabled experimental determination of spin-spin coupling constants and relaxation rates of quadrupole bromine nuclei, both types of parameters being hardly accessible by direct measurements. Investigation of the relaxation behavior of these molecules, being of similar size and shape, has provided quite different practical and interpretational problems which are likely to be encountered in relaxation studies of many other carbon-bromine systems. In order to evaluate the quality of the obtained experimental results, advanced theoretical calculations of the indirect (1)J((13)C,(79)Br) coupling constants, magnetic shielding of carbon nuclei, and quadrupole coupling constants of bromines in the investigated compounds have been performed and compared with the experimental values. Relatively small divergences between experiment and theory have been found. The contributions of the relativistic effects to the values of the discussed parameters have been tentatively estimated.

Structural, magnetic and electrical properties of one-dimensional tetraamidatodiruthenium compounds

The first bromo and iodo tetraamidatodiruthenium compounds of the type [Ru2X(μ-NHOCC6H4-R)4]n [X = Br, R = o-Me (1), m-Me (2), p-Me (3); X = I, R = o-Me (4), m-Me (5), p-Me (6)] have been prepared using solvothermal or microwave activation procedures. In these reactions ethanol or methanol as solvents have been used to make the synthesis procedures more environment-friendly. Solvothermal synthesis has allowed us to isolate single crystals of these extremely insoluble compounds and the crystal structures of all of them have been determined using single crystal X-ray diffraction. The change of the bridging halide ligand permits us to discuss the properties of these complexes on the basis of their structure. Complex 1 shows a Ru-Br-Ru angle of 180.0° whereas in complexes 2-6 the Ru-X-Ru angle varies from 110.16(2) to 115.39(4)°. In all compounds the ruthenium atom has a cis-RuN2O2 environment except in compound 1 that shows a positional disorder of N and O atoms. The bromide complex 1 shows a linear arrangement of the paddlewheel units in the resulting 1D coordination polymer. The fit of the magnetic data indicates that these compounds have non-negligible values of zero-field splitting with D values ranging from 41.10 to 60.10 cm(-1) and antiferromagnetic coupling constants from 0.00 to -4.13 cm(-1). Compound 1 is the first linear paddlewheel diruthenium compound that does not show a maximum in the representation of the magnetic susceptibility towards temperature. The electrical conductivity measurements in the temperature range 300-400 K of compounds 1, 4 and [Ru2Cl(μ-NHOCC6H4-o-Me)4]n (7) show that these compounds present semiconducting behaviours with conductivity values at 400 K in the range 0.3-3.0 × 10(-8) S cm(-1) for the Cl derivative (7), 7-18 × 10(-8) S cm(-1) for the Br derivative (1) and 27-68 × 10(-8) S cm(-1) for the I derivative (4) with average values of 1.4 × 10(-8), 13 × 10(-8) and 47 × 10(-8) S cm(-1), respectively.

Scalar Relaxation of the Second Kind — A Potential Source of Information on the Dynamics of Molecular Movements. 2. Magnetic Dipole Moments and Magnetic Shielding of Bromine Nuclei

In this paper, we continue the exploration of possibilities, limitations, and methodological problems of the studies based on measurements of the nuclear spin relaxation rates running via the scalar relaxation of the second kind (SC2) mechanism. The attention has been focused on the (13)C-(79)Br and (13)C-(81)Br systems in organic bromo compounds, which are characterized by exceptionally small differences of Larmor frequencies, ΔωCBr, of the coupled nuclei. This unique property enables experimental observation of longitudinal SC2 relaxation of (13)C nuclei, which makes investigation of the SC2 relaxation rates an attractive experimental method of determination of spin-spin coupling constants and relaxation rates of quadrupole bromine nuclei, both types of parameters being hardly accessible by direct measurements. A careful examination of the methodology used in SC2 relaxation studies of carbon-bromine systems reveals, however, some disturbing facts that could burden the results with systematic inaccuracies. Namely, the way of calculating the Larmor frequency differences between (13)C and bromine isotopes, ΔωCBr, may cause some reservations. In this work, the values of (79)Br and (81)Br magnetogyric ratios have been rechecked using bromine NMR data for the KBr·Kryptofix 222 complex in acetonitrile solution and the results of the advanced calculations of the magnetic shielding of the bromine nucleus in the Br(-) anion. Moreover, it has been pointed out that in the case of (13)C-(79)Br, the magnetic shielding of the bromine nucleus in the investigated molecule must not be neglected during the calculation of the ΔωCBr parameter. Some recommendations concerning the exploitation of available theoretical methods to calculate bromine shielding constants for bromo compounds have also been formulated, keeping in mind relativistic effects.

Synthesis of some Heterocyclic Compounds Derived from

The 4-(?-bromo acetyl)-4?-toluene sulfonanilide (2) was used as key intermediate to synthesize new heterocyclic compounds. This bromo compound was synthesized via sulfonation of amino group of p-amino acetophenone using Hinsburg method with 4-toluene sulfonyl chloride to form 4-acetyl-4?-toluene sulfonanilide (1) which is used as a starting material in this work. This compound was brominated to yield compound (2) which is used as a precursor to synthesize new five and seven membered heterocyclic compounds such as substituted 1,3-oxazoles (3,4), 1,3-thiazole derivatives (5-7), thiourea compounds (8a,b), 1,3-Thiazoline-2-thione compounds (9a-f) and 1,2,5-triazepine compounds (11a-d). The synthesized compounds were identified depending upon physical, FT-IR and UV spectroscopic data.

Synthesis of some Heterocyclic Compounds Derived from

The 4-(?-bromo acetyl)-4?-toluene sulfonanilide (2) was used as key intermediate to synthesize new heterocyclic compounds. This bromo compound was synthesized via sulfonation of amino group of p-amino acetophenone using Hinsburg method with 4-toluene sulfonyl chloride to form 4-acetyl-4?-toluene sulfonanilide (1) which is used as a starting material in this work. This compound was brominated to yield compound (2) which is used as a precursor to synthesize new five and seven membered heterocyclic compounds such as substituted 1,3-oxazoles (3,4), 1,3-thiazole derivatives (5-7), thiourea compounds (8a,b), 1,3-Thiazoline-2-thione compounds (9a-f) and 1,2,5-triazepine compounds (11a-d). The synthesized compounds were identified depending upon physical, FT-IR and UV spectroscopic data.

ChemInform Abstract: Improved Synthesis of 3‐(Aminoaryl)coumarins.

AbstractA new method is given for the amination of aromatic bromo compounds using trifluoroacetamide as ammonia source and the system CuI/DMEDA as catalyst.

Use of Silver Cathodes to Promote the Direct Reduction and Intramolecular Cyclization of ω-Halo-1-phenyl-1-alkynes in Dimethylformamide

Electrochemical reduction of 6-bromo- and 6-iodo-1-phenyl-1-hexyne and of 7-bromo- and 7-iodo-1-phenyl-1-heptyne at a silver cathode in dimethylformamide (DMF) containing 0.050 M tetramethylammonium perchlorate (TMAP) has been investigated with the aid of cyclic voltammetry and controlled-potential (bulk) electrolysis. Cyclic voltammograms for each bromo compound show a single irreversible cathodic peak for scission of the carbon–bromine bond, whereas two irreversible cathodic peaks are associated with reduction of the carbon–iodine bond of each iodo species. Radical intermediates arising from one-electron reduction of these ω-halo-1-phenyl-1-alkynes at silver undergo intramolecular cyclization to afford benzylidenecycloalkanes; other products include alkynes, enynes, and dimeric species. Electrolyses of 6-iodo-1-phenyl-1-hexyne and 7-iodo-1-phenyl-1-heptyne afford the desired benzylidenecycloalkane in higher yield than do electrolyses of the corresponding brominated compounds. Benzylidenecyclopentane is obtained in up to 85% yield when 6-iodo-1-phenyl-1-hexyne is reduced at a silver electrode held at a potential that corresponds to the first cathodic peak for this substrate; moreover, if the solvent–electrolyte is dried with activated alumina, one can achieve 99% conversion of 6-iodo-1-phenyl-1-hexyne to benzylidenecyclopentane. Studies involving the use of a deuterium atom donor (DMF-d7) or a deuterium ion donor (D2O) offer evidence that radicals and carbanions are both involved as intermediates in the formation of products.

Electrochemical Reformatsky reaction of α-haloketones and benzaldehyde on a graphite powder cathode free of organic solvents

Six α-haloketones adsorbed on a graphite powder cathode were reduced in the presence of benzaldehyde using undivided cell, inert anode and aqueous electrolyte. High yields of aldol coupling product were obtained from 2-chloropinacolone in the presence of catalytic amounts of silver. For the corresponding bromo compound, the reaction was much less satisfactory. Chloroacetone gave moderate yields of the α,β-unsaturated coupling product. 2-Chlorobutanone produced two main products in low yield: the expected aldol and the corresponding 1,3-diketone. With 2-bromopropiophenone and 2-bromoisobutyrophenone no coupling with benzaldehyde was observed but only reductive dehalogenation. The results can be interpreted in terms of a carbanionic intermediate generated by a two-electron transfer.

Isostructurality in the Guest Free Forms and in the Clathrates of 1,3,5-Triethyl-2,4,6-tris(4-halophenoxy)methylbenzenes

Crystal structures of the guest free forms and some solvates of 1,3,5-triethyl-2,4,6-tris(4-halophenoxy)methylbenzenes (1X, X = I, Br, Cl, F) have been studied. The guest free forms of 1I, 1Br, and 1Cl are isostructural, but the crystal structure of 1F is different from the heavier halogen analogues. An entirely different crystal structure of the Me analogue, which is known to be isosteric to the corresponding bromo compound, shows the importance of the electronic factors of the halogens in this series of structures. 1I and 1Br form four types of architectures in their solvates depending upon the inter-halogen interaction geometries. All these solvates are two dimensionally isostructural to the guest free form. 1Cl forms three different types of frameworks in its solvates, and the ethylacetate solvates of the 1I, 1Br, and 1Cl are isostructural. 1F forms only one type of solvate which is isostructural to the corresponding 1Cl solvate.

Synthesis and Crystallography of 8-Halonaphthalene-1-Carbonitriles and Naphthalene-1,8-Dicarbonitrile

A convenient and high-yielding three-step synthesis of 8-halonaphthalene-1-carbonitriles has been achieved by ring opening of 1H-naphtho[1,8-de][1,2,3]triazine with the corresponding halides as the key step. Naphthalene-1,8-dicarbonitrile also has been synthesised from 8-bromonaphthalene-1-carbonitrile via palladium-catalysed cyanation of the aryl bromide. The crystal structures of 8-chloronaphthalene-1-carbonitrile, the A polymorph of the bromo analogue, and naphthalene-1,8-dicarbonitrile are isomorphous with orthorhombic symmetry. The B polymorph of the bromo compound and the iodo analogue are also isomorphous, but with monoclinic symmetry. In all of the halo carbonitriles, the molecules are disordered with respect to the location of the halogen atoms and the nitrile groups. There are no intermolecular X···NC interactions in any of the solids.

A novel method for bromodecarboxylation of α,β-unsaturated carboxylic acids using catalytic sodium nitrite

A first novel synthetic utility of catalytic sodium nitrite in combination with aqueous HBr, for bromo decarboxylation of α,β-unsaturated carboxylic acid is described. α,β-Unsaturated carboxylic acid compounds successfully converted into corresponding bromo compounds. The advantages of this protocol are shorter reaction time and moderate to good yields.