Boron Trifluoride Research Articles

A novel HBI-based ratiometric fluorescent probe for rapid detection of trifluoroborate.

A 2-(2'-hydroxyphenyl)benzimidazole (HBI)-based ratiometric fluorescent probe, known as BTEP, was synthesized using 5-bromosalicylaldehyde as the raw material via Sonogashira coupling and condensation reaction. This probe was designed for rapid detection of boron trifluoride solutions and gases. The N and O coordination atoms in the probe undergo a boron difluoride addition with BF3, which affects the process of excited state intramolecular proton transfer (ESIPT) leading to a blue shift of fluorescence emission. Obvious changes in the fluorescence signal can be observed within 60 seconds. The introduction of an acetylene trimethylsilane fragment increases the conjugate plane and is beneficial to improving the selectivity of the probe. The I408/I479 fluorescence ratio of the probe displays a linear relationship with the concentration of BF3 in the range of 5-50 μM, with a detection of limit as low as 69.5 nM. Furthermore, the probe demonstrates specific and selective recognition of BF3 among eight common interference substances. Test strips prepared using BTEP have the capability of real-time naked-eye detection of trace BF3 gas.

High Yield Synthesis of Curcumin and Symmetric Curcuminoids: A “Click” and “Unclick” Chemistry Approach

The worldwide known and employed spice of Asian origin, turmeric, receives significant attention due to its numerous purported medicinal properties. Herein, we report an optimized synthesis of curcumin and symmetric curcuminoids of aromatic (bisdemethoxycurcumin) and heterocyclic type, with yields going from good to excellent using the cyclic difluoro-boronate derivative of acetylacetone prepared by reaction of 2,4-pentanedione with boron trifluoride in THF (ca. 95%). The subsequent cleavage of the BF2 group is of significant importance for achieving a high overall yield in this two-step procedure. Such cleavage occurs by treatment with hydrated alumina (Al2O3) or silica (SiO2) oxides, thus allowing the target heptanoids obtained in high yields as an amorphous powder to be filtered off directly from the reaction media. Furthermore, crystallization instead of chromatographic procedures provides a straightforward purification step. The ease and efficiency with which the present methodology can be applied to synthesizing the title compounds earns the terms "click" and "unclick" applied to describe particularly straightforward, efficient reactions. Furthermore, the methodology offers a simple, versatile, fast, and economical synthetic alternative for the obtention of curcumin (85% yield), bis-demethoxycurcumin (78% yield), and the symmetrical heterocyclic curcuminoids (80-92% yield), in pure form and excellent yields.

Boron Trifluoride‐Mediated Synthesis of Oxazole N‐oxides

AbstractA new synthetic protocol for the preparation of oxazole N‐oxides in the form of stable boron trifluoride complexes has been developed. It is based on the condensation of α‐diketone monooximes with an appropriate aldehyde component in the presence of an equimolar amount of boron trifluoride. The method opens access to a broad scope of derivatives including previously unknown 2‐unsubstituted oxazole N‐oxides. Its abilities were demonstrated via the synthesis of 25 diverse oxazole derivatives in 14–89 % yields.

Lewis basicity of alkyl carbonates and other esters. The Gutmann Donor Number (DN), a flawed indicator? Boron trifluoride adduct-formation enthalpy, experimentally or computationally determined, as a reliable alternative

Alkyl carbonates are essential components in the manufacture of lithium-ion batteries, as electrolytes or additives. The Lewis basicity of alkyl carbonates and other carbonyl compounds used in electrochemistry are often characterized by their Donor Number (DN). Assessment of the literature DN values displays great discrepancies. This is attributed in part to experimental errors, but mostly to inconsistent methods of determination. An alternative Lewis basicity scale is proposed, based on the enthalpy of adduct formation of a Lewis base with BF3 in dichloromethane solvent -ΔH(BF3). Experimental data are well reproduced by a modified ab initio G4 method and a mixed cluster-continuum approach of solvation. These calculations permit a confident estimation of previously not measured -ΔH(BF3) values. The combination of a large set of experimental data and of calculations provides a consistent source of Lewis basicity of molecules used in electrochemistry and related fields.

SELENOLANES, SELENATRANS AND ESTERS OF SELENIC ACID

It is known that selenic acid and selenium dioxide act as oxidizing agents in reactions with α-oxides when heated. The proposed paper presents data on the synthesis of organoselenium compounds based on reactions of α-oxides with selenic acid and its anhydride, where the latter act as selenation agents. It was found that in the presence of catalytic amounts of boron trifluoride esterate in the reactions of oxiranes with acid the oxirane ring opens both according to the rule and against the Krasussky rule with the formation of a mixture of α- and β- isomers of selenic acid esters. In contrast to the acid, the reactions of oxiranes with selendioxide involve the expansion of the oxirane ring to form functionally substituted selenolanes. This paper is followed by the analysis of the literature material on atranes, a unique class of heterocyclic compounds with distinct biologically active properties, and their element derivatives (B, Ge, Si, etc.). For the first time we have synthesized selenatranol, which is not described in the literature. In future it may not only possess bioactive properties in itself, like the majority of organoselenium compounds, but also be a drug precursor. Acetylselenatranol was synthesized by the reaction of selenatranol with acetic anhydride in acid medium. The data of IR, PMR spectra and elemental analysis of the synthesized compounds as well as the data of thermogravimetric (TGA) and differential thermal analysis (DTA) of some of them are given

Mechanical Force Enables an Anomalous Dual Ring-Opening Reaction of Naphthodipyran.

Multimodal mechanophores that exhibit complex mechanochromic behavior beyond the typical binary response are capable of distinguishing between multiple stress states through discrete changes in color. Naphthodipyran photoswitches contain two pyran rings fused to a central naphthalene core and represent a potentially promising framework for multimodal reactivity. However, the concurrent ring opening of both pyran moieties has previously proven inaccessible via photochemical activation. Here, we demonstrate that mechanical force supplied to naphthodipyran through covalently linked polymer chains generates the elusive dual ring-opened dimerocyanine product with unique near-infrared absorption properties. Trapping with boron trifluoride renders the merocyanine dyes thermally persistent and reveals apparent sequential ring-opening behavior that departs from the reactivity of previously studied mechanophores under the high strain rates imposed by ultrasound-induced solvodynamic chain extension.

Boron Trifluoride Etherate Promoted Regioselective 3-Acylation of Indoles with Anhydrides

An efficient, high-yielding and scalable procedure for the regioselective 3-acylation of indoles with anhydrides promoted by boron trifluoride etherate under mild conditions was reported. This novel protocol provided a simple way to prepare 3-(benzofuran-2-yl) indole in three steps.

Bioactivity and Cell Imaging of Antitumor Fluorescent Agents (Curcumin Derivatives) Coated by Two-Way Embedded Cyclodextrin Strategy.

Curcumin has a wide range of pharmacological activities, which can be used to treat tumors, inflammation and other diseases. However, curcumin's poor solubility and low bioavailability limit its application. In this article, the structure of curcumin was modified with boron trifluoride ether to change fluorescent labeling. The compounds were then embedded into the hydrophobic cavity of α-cyclodextrin and hydroxypropyl β-cyclodextrin to form inclusion complexes. The two inclusion complexes have excellent photophysical properties, and the maximum emission wavelength is in the range of 550-565 nm. In addition, the two compounds were applied to the fluorescence imaging of HCT-116 cells and HeLa cells, and the proliferation toxicity of the compounds was detected. Both compounds showed certain inhibitory effects on the proliferation of cancer cells. In short, the fluorescent drug molecule synthesized in this article has great reference value for the development of new dosage forms of curcumin.

Performance Improvement of Lithium Metal Batteries Enabled By LiBF3CN as a New Electrolyte Additive

A newly synthesized electrolyte additive, lithium trifluoro(cyano) borate (LiBF3CN), has been investigated for electrochemical performance improvement of lithium metal batteries. The LiBF3CN has a structure where one fluorine atom of BF4 − is substituted with a cyano group (−CN) prepared by the reaction of boron trifluoride etherate with lithium cyanide. The electrochemical performance in symmetric Li/Li cells and NCM523/Li cells is significantly improved upon the incorporation of LiBF3CN as an electrolyte additive into a carbonate-based electrolyte. Extensive characterization of the deposited lithium metal reveals that a thin (≈20 nm) and robust SEI composed of LiNxOy, Li3N and Li2O is formed by the reductive decomposition of the LiBF3CN additive, which plays an important role in decreasing the resistance and stabilizing lithium deposition/stripping. The insight into the substitution effect of a functional group obtained from this work provides guidance for the design of new electrolyte additives.

Boron Trifluoride Etherate-Controlled Reactions of Methyl Enol Ethers: Selective Synthesis of Dihydrofuro[3,2-c]chromenone and Furo[3,2-c]chromenone Derivatives

AbstractA facile one-step synthetic approach to dihydrofuro-[3,2-c]chromenones and furo[3,2-c]chromenones by the reaction of methyl enol ethers with 4-hydroxycoumarins under metal-free conditions is presented. Dihydrofuro[3,2-c]chromenones and furo[3,2-c]-chromenones were selectively obtained by controlling the stoichiometry of boron trifluoride diethyl etherate. An unexpected aryl-group migration followed by aromatization of the furan moiety, leading to a variety of furo[3,2-c]chromenone derivatives in good yields, is reported.

Preparation and performance in IR and UV of transparent inorganic polysiloxane coating with dispersed TiO2 on glass substrates

The aim of the presented work was to develop an economical, transparent coating with dispersed TiO2 dispersion and inorganic polysiloxane resin for glass windows application and to study its effectiveness in filtering IR and UV radiations. Two oligomeric silanes were prepared in different molar ratios to produce inorganic polysiloxane resin. They were tested for their viscosity to reflect the completion of the reaction and form an amide linkage. FTIR was done to support the viscosity result by proving the presence of amide linkages. 10%, 20%, and 30% of compounded TiO2 were successfully dispersed in 0.3% sodium sulfosalicylate (dehydrated ethanol). Each TiO2 concentration was characterized for size distribution and polydispersity index (PDI). Additives solutions of 2-hydroxybenzophenone (HBP) and boron trifluoride (BF3) were also soluted in the same solvent. Glass substrates were coated with the formulations and tested for curing and hardness properties. Windows Energy Profiler (WEP) was used to study the UV, IR, and daylight transmission of the coated glasses. Each inorganic polysiloxane resin showed various viscosity values before reaching a constant state which designates complete formations of amide linkages. Polysiloxane resin with a viscosity value of 30.5 mPa/s was the most ideal to act as a binder. FTIR characterization proved the formation of amide linkages. The particle size distribution of TiO2 recorded the size of 87 nm after dispersion with correlating value of 1 PDI. The fastest drying time of 3 hours was recorded. The pencil hardness test quoted 6H pencil as the hardest pencil grade. WEP analysis of UV, IR, and daylight transmission gives satisfactory results of 0%, 7%, and 61%, respectively. Laboratory analysis for viscosity tests often being held off. The test requires the samples to be transferred in a cylinder with an open-air spindle rotation. Samples react with the surrounding environment. Thus, polymerization takes place rapidly, resulting in hardened samples inside the cylinder. The different measure was taken by wrapping the testing area with aluminium foil. This research was conducted under equatorial climate. The obtained test results may contribute to the conclusion of transparent TiO2 nano-particles coating on glass substrates for windows application. This can reduce the electricity usage in buildings for artificial cooling to provide indoor thermal comfort. Smart coating formulations have a noticeable effect on filtering harmful solar radiation. This study presents the economical and undemanding ways to develop transparent smart coating formulation with superior performance against solar radiation. It is expected to have a bright potential in the architectural industry.

Cationic Copolymers of Norbornylized Seed Oils for Fiber-Reinforced Composite Applications.

Norbornylized seed oils, i.e., norbornylized linseed oil (NLO), norbornylized soybean oil (NSO), and norbornylized high oleic soybean oil (NHOSO), were synthesized via the Diels–Alder reaction of seed oil and dicyclopentadiene (DCPD) at high temperature (∼235 °C) and high pressure (∼80 psi), followed by cationic copolymerization using DCPD with boron trifluoride diethyl etherate catalyst. Norbornylized seed oils were characterized using H1 nuclear magnetic resonance (NMR), attenuated total reflectance-Fourier transform infrared, and gel permeation chromatography (GPC). Copolymers were formulated with four different DCPD contents, and curing was investigated using dynamic differential scanning calorimetry (DSC) measurements. It was found that the curing followed NLO > NSO > NHOSO with NLO having the highest exotherm, lowest activation energy, and lowest onset temperature. Furthermore, the gelation times were the least for NLO-DCPD copolymers. As anticipated, the degree of unsaturation and norbornene moieties strongly influenced the curing of copolymer thermosets. The copolymer products were compression-molded into thermosets and characterized by DSC, Soxhlet extraction, thermogravimetric analysis (TGA), H1 NMR, solid-state C13 NMR, and GPC. NLO-DCPD thermosets demonstrated high cure, higher thermal stability, glass transition temperature, and cross-linking capability compared to the other seed oil-DCPD counterparts. NMR and GPC results further suggested that bis-allylic and norbornene units concomitantly participated very actively during the cationic curing reaction. Moreover, scanning electron microscopy images of glass fiber-reinforced NLO-DCPD copolymer composites demonstrated good interfacial adhesion between the polymer matrix and fiber phases, imparting enhanced thermo-mechanical properties. This research opens a new venue for higher biobased greener polymer constituent for composite applications.

One‐Pot Transition‐Metal‐Free Synthesis of Polysubstituted Fused Benzene Derivatives from Methyl Enol Ethers and Alkynes

A one-pot synthesis of polysubstituted fused benzene derivatives from methyl enol ethers and alkynes is reported. A wide variety of diversely functionalized naphthalene and phenanthrene derivatives were obtained in good to excellent yields. Due to the fluorescent nature of naphthalene, selected compounds were screened for the solvatochromism study.

Heptamethine cyanine dye-based functionalized recyclable flexible cotton fabric platform for the colorimetric and real-time ultrasensitive detection of gaseous BF3

In this paper, a near infrared heptamethine cyanine dye of BK-Cy for boron trifluoride (BF3) detection was developed based on the Lewis acid-base reaction mechanism. BF3 bounded to the diphenylamine group in the middle of the heptamethine backbone structure forming Lewis acid-base complexes with decreasing fluorescence at λem = 830 nm (λex = 780 nm) and increased absorbance between 500 and 700 nm, making obvious color changes from light green to dark blue. BK-Cy showed excellent properties including rapid response (<1 min), lowest detection limit (1.73 nM), excellent linearity (R2 = 0.9903) and specific selectivity. Meanwhile, a functionalized recyclable flexible cotton fabric platform of BK-Cy@cotton was fabricated and assembled with a smartphone to form a portable detecting platform to monitor the color changes of BK-Cy for quantitative BF3 detecting in gas phase under visible light. The real-time visualization of the remodeling BK-Cy@cotton platform from BK-Cy through dynamic covalent bonding was completely recyclable, environmentally friendly and had the possibility for future practicability applications.

Synthesis of a new tripod BODIPY dye bearing N-tert-Butoxycarbonyl amine and its acetylation

A new tripod boron dipyrromethene (BODIPY) dye bearing N-tert-butoxycarbonyl (N-Boc) amine side chain was synthesized and the functionality was confirmed by means of its acetylation reaction with acetic anhydride. Deprotection of the N-Boc protective group had been successfully performed using boron trifluoride etherate (BF3·OEt2) solution alone or the combination of BF3·OEt2 and molecular sieves to solve the susceptibility of the BODIPY fluorophore under the protonic acid conditions. All the new structures had been characterized by NMR, HRMS and IR spectra. A conformational isomeric phenomenon was observed originating from partly restricted rotation of the RNH group attached to the 1,3,5-triazine ring. This work made the chemical transformation via amine functionality around meso position in the tripod BODIPY available.

Cascade Synthesis of Luminescent Difluoroboron Diketonate Compounds forRoom‐TemperatureOrganic Afterglow Materials

Comprehensive SummaryDifluoroboron β‐diketonate (BF2bdk) compounds represent an important class of luminescent materials, whereas their synthesis requires multiple steps, which restrict their application in diverse fields. Here we report a cascade reaction to prepare BF2bdk from aromatic ketones, carboxylic acids, trifluoroacetic anhydride and boron trifluoride diethyl etherate. The cascade reaction is very simple and straightforward to produce BF2bdk with desired functional groups in reasonable isolation yields. Further, when some specific BF2bdk compounds are used as luminescent dopants, organic room‐temperature phosphorescence with lifetimes &gt;1.0 s and intense afterglow under ambient conditions can be achieved with the assistance by suitable organic matrices. The dopant‐matrix materials exhibit excellent processability into desired patterns and large‐area panels, and function as efficient donors of excited state energy transfer for the fabrication of red afterglow materials. The materials can be processed into aqueous afterglow dispersion that displays unique property of escaping the interference from strong fluorescence background.

Boron trifluoride etherate for regioselective rearrangement or opening of secondary aryl glycidic amides

A regioselective 1,2-acyl, 1,2-hydrogen migration, and intermolecular opening of secondary aryl glycidic amides catalyzed by BF3·OEt2 were investigated. Derived from this reaction, α-Formyl acid, α-ketoamides, or fluorohydrin derivatives could regioselective be obtained, depending on the nature of the aromatic ring substituent bearing on the oxirane ring. To demonstrate the plausible mechanism in the formation of α-formyl acid or alpha-keto amides derivatives, an isotopic labeling experiment was developed.

Development of a NIR iridium(III) complex for self-calibrated and luminogenic detection of boron trifluoride

Boron trifluoride (BF3) is a potential environmental pollutant, and excess exposure to it may cause human diseases. However, the sensitive, rapid and accurate detection of BF3 for on-site purposes is still a challenge. In this work, we developed the first NIR iridium(III)-based probe with dual emission and a Stokes shift of 370 nm for self-calibrated and luminogenic detection of BF3. This probe exhibited a strong luminescence enhancement at around 650 nm to BF3 (0–100 μM) with almost no change in luminescence at 475 nm, displaying a 220-fold I650 nm/I475 nm enhancement at 100 μM of BF3 with a detection limit of 0.35 μM. Moreover, the probe showed a fast response time of less than 5 s to BF3 along with an obvious color change under UV irradiation for visual detection. Importantly, the desirable photophysical properties of the iridium(III)-based probe can be harnessed for time-resolved detection of BF3 in the presence of the fluorescence background. The applicability of the probe was further verified in an organic solvent waste-spiked system and on a glass pane. This work will provide a solid basis for the development of sensitive and on-site BF3 sensing toolkits for environmental monitoring.

BF3 Mediated [1,5]‐Hydride Shift Triggered Cyclization: Thioethers Join the Game

Abstract2‐(2‐(Benzylthio)benzylidene)malonates can undergo the 1,5‐hydride shift triggered cyclization resulting in thiachromanes in 45–84 % yield. Boron trifluoride as a reaction promotor is the key to success. DFT calculations revealed that the reaction proceeds via a chelate BF2 complex, which was confirmed by NMR‐analysis. Experimental and theoretical comparison of nitrogen, sulfur and carbon analogues revealed that sulfur derivatives have the highest activation barrier for the hydride transfer due to the unfavorable transition state geometry, which explains the lack of previous reports on 1,5‐hydride shifts in (alkylthio)styrenes.

Low-cost synthesis of small molecule acceptors makes polymer solar cells commercially viable

The acceptor-donor-acceptor (A–D–A) or A–DA’D–A structured small molecule acceptors (SMAs) have triggered substantial progress for polymer solar cells (PSCs). However, the high−cost of the SMAs impedes the commercial viability of such renewable energy, as their synthesis via the classical pyridine-catalyzed Knoevenagel condensation usually suffers from low reaction efficiency and tedious purifying work-up. Herein, we developed a simple and cheap boron trifluoride etherate-catalyzed Knoevenagel condensation for addressing this challenge, and found that the coupling of the aldehyde-terminated D unit and the A-end groups could be quantitatively finished in the presence of acetic anhydride within 15 minutes at room temperature. Compared with the conventional method, the high reaction efficiency of our method is related to the germinal diacetate pathway that is thermodynamically favorable to give the final products. For those high performing SMAs (such as ITIC-4F and Y6), the cost could be reduced by 50% compared with conventional preparation. In addition to the application in PSCs, our synthetic approach provides a facile and low-cost access to a wide range of D–A organic semiconductors for emerging technologies.