Boron Exchange Research Articles

Bidentate boron Lewis acids: synthesis by tin boron exchange reaction and host-guest complex formation.

Four bidentate boron Lewis acids based on the 1,8-diethynylanthracene backbone have been synthesized by a tin-boron exchange reaction with various chloroboranes, yielding the products in good to excellent yields. Complexation experiments of the host compounds with pyridine, pyrimidine and TMEDA demonstrated striking differences in terms of formation and solubility of the supramolecular adducts. The host-guest complexes were investigated by multinuclear NMR spectroscopy and structurally characterized by X-ray diffraction experiments, illustrating the adaptation of the host system upon adduct formation with different neutral guest molecules.

Alkylated Boroles from Aluminum–Boron Exchange

Alkylated Boroles from Aluminum–Boron Exchange

Light-Mediated Sulfur-Boron Exchange.

Interaction of sulfides bearing a tetrafluoropyridinyl group with bis(catecholato)diboron followed by treatment with pinacol and triethylamine affording pinacol boronic esters is described. The reaction is promoted by an organic photocatalyst (3DPA2FBN) under irradiation with 400 nm light, and works with primary, secondary, and tertiary sulfides. The electron depleting character of the fluorinated pyridine fragment plays an important role in generating alkyl radicals.

Lewis Acid Assisted C–CN Cleavage of Benzonitrile Using [(dippe)NiH

Reactions of [(dippe)NiH]2 with benzonitrile and varying concentrations of Lewis acids (primarily BPh3 and BF3) have shown a dramatic variation of reaction rate compared to the same reaction without Lewis acids. When less than one equivalent of Lewis acid is used, the reaction rate is as much as 100 times greater than without Lewis acid. Boron exchange was observed with less than one equivalent of Lewis acid allowing the formation of a Ni(0)–η2-aryl complex (observed by low-temperature NMR and calculations) to which the Lewis acid is postulated to re-coordinate as the rate-limiting step allowing the formation of a stable Ni(II) product. When one equivalent or greater of Lewis acid is used, the reaction shows dramatic inhibition even compared to the reaction without Lewis acid. Lewis acid dissociation can be considered as the rate-limiting step under these conditions. The overall work detailed herein has shown the importance of Lewis acids in the activation of benzonitriles due to the strengthening of the C–N bond allowing for increased stabilization of the products.

Diverse Transformations of Boronic Compounds Promoted by Hypervalent Organoiodines(III): Unique Combined Reactivity of Two Electrophilic Compounds

AbstractBoth hypervalent organoiodine(III) compounds and boronic acids/esters are non‐toxic and considered as environment‐friendly compounds and have had a remarkable impact on the field of synthetic organic chemistry. Numerous transformations have been carried out using hypervalent organoiodine(III) or boronic acids/esters – taken separately – with other reactants, but transformations with these two reagents taken together are comparatively less well reported. In this mini‐review, diverse reactions carried out with these two substrates in the presence of each other, have been discussed. Various functionalizations of boronic compounds, promoted by hypervalent organoiodine(III) reagents, both in the presence and absence of transition metals, have been reviewed. Different metal‐free iodine(III)–boron exchange reactions providing iodonium salts, various ipso transformations of boronic acids/esters and metal‐catalyzed cross‐coupling reactions of boronic compounds with hypervalent organoiodine(III) reagents are the prime focal areas of this article. Mechanistic aspects for certain reactions have also been delineated.magnified image

Full factorial design of experiments for boron removal from solutions by Purolite S 108 resin converted to hydroxyl form

ABSTRACTIn this study, boron removal from synthetic solutions using Purolite S 108 resin converted to hydroxyl form was investigated. Experiments were carried out in batch mode as a function of pH (4–10), concentration (50–500 mg/L), and resin-to-solution ratio (1–2.5 g/50 mL). Optimum pH value was determined as 10 and exchange capacity increased with increasing concentration. Boron exchange capacity of the resin increased at low solid-to-solution ratios. A 23 full factorial experimental design was applied to determine the optimum values and degree of importance of parameters. The low (1) and high (2) levels of the parameters were 3 and 7 for pH, 500 and 1,000 mg/L for concentration, and 1 and 2 g/50 mL for solid-to-solution ratio, respectively. The optimization of the parameters was done by interpretation of cube plot and Pareto chart. At 87% confidence level, the importance sequence of parameters and their interaction were as follows: concentration, pH-concentration interaction, and pH had positive effect on capacity. Solid amount, pH-solid amount, and concentration–solid amount interactions had negative effect on the capacity. Maximum capacity was calculated to be 25.5 mg/g. The kinetic data fitted to the pseudo-second-order model and rate controlling steps were liquid film and ash layer diffusion.

Assessing the impact of diagenesis on δ11B, δ13C, δ18O, Sr/Ca and B/Ca values in fossil planktic foraminiferal calcite

The geochemical composition of foraminiferal tests is a valuable archive for the reconstruction of paleo-climatic, -oceanographic and -ecological changes. However, dissolution of biogenic calcite and precipitation of inorganic calcite (overgrowth and recrystallization) at the seafloor and in the sediment column can potentially alter the original geochemical composition of the foraminiferal test, biasing any resulting paleoenvironmental reconstruction. The δ11B of planktic foraminiferal calcite is a promising ocean pH-proxy but the effect of diagenesis is still poorly known. Here we present new δ11B, δ13C, δ18O, Sr/Ca and B/Ca data from multiple species of planktic foraminifera from time-equivalent samples for two low latitude sites: clay-rich Tanzanian Drilling Project (TDP) Site 18 from the Indian Ocean containing well-preserved (‘glassy’) foraminifera and carbonate-rich Ocean Drilling Program (ODP) Site 865 from the central Pacific Ocean hosting recrystallized (‘frosty’) foraminifera. Our approach makes the assumption that environmental conditions were initially similar at both sites so most chemical differences are attributable to diagenesis. Planktic foraminiferal δ18O and δ13C records show offsets in both relative and absolute values between the two sites consistent with earlier findings that these isotopic ratios are strongly influenced by diagenetic alteration. Sr/Ca and B/Ca ratios in planktic foraminiferal calcite are also offset between the two sites but there is little change in the relative difference between surface and deep dwelling taxa. In contrast, δ11B values indicate no large differences between well-preserved and recrystallized foraminifera suggesting that despite extensive diagenetic alteration the δ11B of biogenic calcite appears robust, potentially indicative of a lack of free exchange of boron between pore fluids and the recrystallizing CaCO3. Our finding may remove one potential source of uncertainty in δ11B based pH reconstructions and provide us with greater confidence in our ability to reconstruct pH in the ancient oceans from at least some recrystallized foraminiferal calcite. However, further investigations should extend this approach to test the robustness of our findings across a range of taphonomies, ages and burial settings.

Chemoselective Tin–Boron Exchange Aided by the Use of Dummy Ligands at the Tin Atom

C(sp2)–Sn bonds generally react more quickly than C(sp3)–Sn bonds in tin–boron exchange processes, and discrimination between (hetero)aryl groups to be transferred from tin to boron and those to remain at the tin atom (usually methyl groups) is reliable. Conversely, transmetalation of benzylic carbon–tin bonds is disfavored, and the chemoselectivity against other C(sp3)–Sn bonds at the tin atom is poor. That inherent problem is overcome by the installation of one or more Me3SiCH2 (TMSM) groups at the tin atom as nontransferable substituents. With these groups, the tin–boron metathesis of benzylic C(sp3)–Sn bonds occurs cleanly and rapidly. The efficiency of the new method is demonstrated in the demanding synthesis of C6F5-substituted dihydroborepines with binaphthyl backbones.

Evaluation of Soil Degradation Impact on Wheat Yield by Geographical Information System

Soil degradation and its relation to wheat yield were analyzed in a 1041.2-ha catchment in Ustic soil moisture regime in north-central Anatolia, Turkey. The soils in the study area were sampled based on a randomized sampling scheme, using 142 samples from topsoil and 115 samples from subsoil. All the soil samples were analyzed for sand, silt, clay, coarse material (material with a diameter of >2 mm), soil organic matter, phosphorous, nitrogen, boron, zinc, iron, electrical conductivity, pH, hydraulic conductivity, and cation exchange capacity. Wheat yield was measured at 115 sampling locations. Data were evaluated by global information system (GIS) will and variable reduction (factor analysis) techniques. The majority of the soil properties exhibited high variation with a skewed distribution. Low organic-matter content, high penetration resistance, low water-holding capacity, and deficiency in some macro- and microelements were the most important factors limiting wheat yield.

Preparation of a Solid Adsorbent Derived from Concrete Sludge and its Boron Removal Performance

We prepared a solid adsorbent for boron removal using real concrete sludge. The sludge was diluted with water at dilution ratios from 1 to 15. The diluted concrete sludge was then filtered and dried. Two types of drying methods were examined: natural drying under atmospheric conditions and forced drying in an oven at 105 °C. The boron removal performance was examined using a boric acid solution containing 100 mgB/L. All of the adsorbents prepared showed boron removal capacity. The adsorbent prepared with dilution ratio 10 and forced drying exhibited the highest boron removal capacity; the boron concentration after 24 h was just 3.33 mg/L, which is below the Japanese standard for industrial effluent (10 mg/L), and the maximum adsorption capacity for boron was 50 mgboron/gadsorbent. The drying method had a significant effect on both the rate and capacity of boron removal. With natural drying under atmospheric conditions, the adsorption initially proceeded quickly, but the final amount adsorbed was lower than that for the force-dried adsorbents. The boron removal can be attributed to ion exchange and uptake of boron in the ettringite phase. These results indicate that boron adsorbents prepared from concrete sludge can be applied for the removal of boron from effluents.

Diastereoselective Synthesis of 1,2,3‐Substituted Potassium Cyclopropyl Trifluoroborates via an Unusual Zinc—Boron Exchange.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Family of Main-Chain Polymeric Lewis Acids: Synthesis and Fluorescent Sensing Properties of Boron-Modified Polythiophenes

A new family of main-chain organoborane polymeric Lewis acids (PTh-BAr) that contain Lewis acidic boron groups embedded into a polythiophene backbone has been prepared under mild conditions through tin-boron exchange reaction. When phenyl and pentafluorophenyl groups are attached to boron, blue and green luminescence is observed, respectively, while the attachment of ferrocenyl substituents leads to a characteristic red color. The incorporation of readily accessible highly Lewis acidic groups into the conjugated polymer backbone provides an opportunity for sensing of Lewis basic substrates. For instance, treatment of the polymer containing phenyl substituents on boron with pyridine leads to efficient quenching of the fluorescence, while the polymer containing ferrocenyl groups changes color from dark red to light orange.

3+1]-Cyclisierungen zu Tetraboraporphyrinogenen / [3+1]-Cycloadditions with Formation of Tetraboraporphyrinogenes

Abstract 2,5-Bis(chloro-2,2,6,6-tetramethylpiperidinoboryl)thiophene (1) and 2,5-bis(chloro-diisopropylaminoboryl) pyrrol (4) react with two equivalents of 2-lithiothiophenide to yield the corresponding 2,5-diborylheteroarenes (2,5) in which two boryl groups connect three heteroarenes. After lithiation of the terminal thiophenes of both compounds in 5,5'-position their reactions with the diborylthiophene 1 as well as with diborylpyrrol 4, lead to tetraboraporphyrinogenes (3, 6), the latter being the first tetraboratetraazaporphyrinogene. By silicon / boron exchange of 1-trimethylsilylimidazol with the 2,5-diborylpyrrol 4 the 2,5-bis(imidazolyldiisopropylamino- boryl)pyrrol 7 is formed, which reacts with BH3 and BEt3 to give the N-borane adducts of 7. The spectroscopic data and four X-ray structure analyses are reported.

ChemInform Abstract: An Alternative General Preparation of 2-Alkyl-1-benzostannepines and Their Conversion into 1-Benzostibepines and 1-Benzoborepines via a Tin-Metal Exchange.

The 2-alkyl-1-benzostannepines 4a–g were prepared by the intramolecular hydrostannation of the tin intermediates 3 to an acetylenic moiety in one pot from (Z)-1-(o-bromophenyl)but-1-en-3-ynes 1. The obtained stannepines 4 were easily converted into the 1-benzostibepines 9, 10, 11, 12 and the 1-benzoborepines 14, 15 by tin–antimony and tin–boron exchange reactions in moderate to good yields, respectively. The 1-benzoborepines 14 and 15 are hitherto unknown heterocyclic ring systems.

An alternative general preparation of 2-alkyl-1-benzostannepines and their conversion into 1-benzostibepines and 1-benzoborepines via a tin–metal exchange †

The 2-alkyl-1-benzostannepines 4a–g were prepared by the intramolecular hydrostannation of the tin intermediates 3 to an acetylenic moiety in one pot from (Z)-1-(o-bromophenyl)but-1-en-3-ynes 1. The obtained stannepines 4 were easily converted into the 1-benzostibepines 9, 10, 11, 12 and the 1-benzoborepines 14, 15 by tin–antimony and tin–boron exchange reactions in moderate to good yields, respectively. The 1-benzoborepines 14 and 15 are hitherto unknown heterocyclic ring systems.

Synthesis and Solid State 11B-{1H} Mas Nmr Investigations of some Group 11 arachno-2-Metallatetraboranes

The preparation and characterization (melting point, solution 11B-{1H} NMR, IR) of some new 2-arachno-argentatetraboranes and 2-arachno-cupratetraboranes, [2-{(R3P)2M}B3H8] {M = Ag, R = 2-MeC6H4, 4-CIC6H4, 4-MeOC6H4, 2,6-(MeO)2C6H3; M = Cu, R = 4-CIC6H4, 2,6-(MeO)2C6H3} are reported and their solid state 11B MAS (Magic Angle Spinning) NMR spectra are compared with those obtained from the previously known metallatetraboranes {M = Ag, R = Ph, 4-MeC6H4; M = Cu, R = Ph} and [NMe4][2-{M(CO)4}B3H8] (M = Cr, W). In contrast to the Cr and W derivatives, the Ag and Cu clusters exhibit only one signal in their solid state 11B spectra consistent with an intramolecular boron exchange process which occurs in the solid state. Solid state 11B MAS NMR spectra of Cs[B3H8] and [NMe4][B3H8] are also reported. Referee I: H. Beall Referee II: L. Barton

Equilibrium and transport properties of boron species in anionic membranes

Current efficiency for electric transfer of boric acid across two types of anionic exchange membranes are reported, and related to the condensation of boric acid in solution. Equilibrium properties of boron species in the exchanger have been derived from the variation of the membrane capacity for boron exchange and the sorption of boric acid measured in the concentration range 0–0.55 mol dm −3 of bathing solution. Boron diffusion through the membrane, either in chloride or in borate forms, allows a comparison of passive and facilitated diffusion processes in both types of membranes. Equilibrium and diffusion parameters thus obtained permit the interpretation of electrodialysis experiments which could demonstrate that, for a given concentration of the donor solution, the current efficiency is governed strictly by the average number of boron atoms per exchanging site of the membrane.

Improved Method for Determination of Acetylcholine, Choline, and Other Biogenic Amines in a Single Brain Tissue Sample Using High Performance Liquid Chromatography and Electrochemical Detection

Abstract A simple method for determination of ACh, Ch, NA, DA, 5-HT and their related metabolites on the same brain tissue sample was developed by HPLC-ED. The electrochemical detection system is equipped with a platinum electrode for ACh and Ch detection, or a glassy carbon electrode for CA and 5-HT detection. ACh and Ch can be separated with bonded silica or polystyrene reverse phase columns, using a pH 7 mobile phase. They are converted to H2O2 by the passage of the effluent through an in line post column reactor with covalently bonded ACh esterase and Ch oxidase. This step ensures sensitivity, reliability and enzyme economy. Tissue preparation consists of formic acid/acetone extraction and purification by tetraphenyl boron exchange with high reproductible recoveries. The time necessary for the whole procedure is short, making it well adapted to large series. CA, 5-HT and related metabolites can be simply analysed on an aliquot of the tissue extract.

After a third of a century in organoboron chemistry

Abstract

Integrated Testing of the Srl-165 Glass Waste Form

AbstractIntegrated testing of the important components of a glass waste form waste package has been performed in order to gain a better understanding of the processes of radionuclide release and transport in the near field environment. Based upon an interpretation of the depth of penetration of hydrogen in reacted SRL-165 glass we have modeled the radionuclide release from the glass as a combined process of (1) the diffusive exchange of alkalis and boron in the glass for hydrogen species in the solution (D=10−16 cm2/s) and (2) surface dissolution. Surface dissolution controls the release of components not exchanged by diffusion and takes place at a rate of 1.5-3.0 μm/yr. Subsequent to release the radionuclides may remain in the leach solution, diffuse into the tuff, or precipitate as secondary phases. Precipitation is particularly important for plutonium and americium. Diffusive transport of radionuclides through the tuff takes place at an extremely slow rate, D=10−16 cm2/s. As such, the mass of radionuclides incorporated in the tuff by diffusion during the tests is inconsequential relative to that in the leach solution (with the exception of plutonium) and can be ignored in mass balance calculations. Mass balance calculations based upon the release of radionuclides by surface dissolution of the glass waste form are in good agreement with observed solution chemistry when allowances are made for a pulse of dissolution early in the tests. This pulse may be due to either the rapid dissolution of high-energy surface features early in the inLegrated tests, or an initially high surface dissolution rate that decreases with time as silica saturation is approached [1], or a combination of the two.