Cesium Fluoride Research Articles

The role of cesium fluoride in aryl propargyl ether Claisen rearrangement and its mechanistic elucidation: a theoretical study

The role of cesium fluoride (CsF) in aryl propargyl ether Claisen rearrangement and its mechanistic pathway have been investigated in gas and solvent phase using the density functional theory implemented in Gaussian 09. Our results indicate that the [3,3]-sigmatropic rearrangement is the rate-limiting step with ΔG ‡ value of 37.1 kcal/mol in solvent phase. Furthermore, the results show that the enolization of α-allenylketone intermediate (Int1-CsF) has a higher free energy barrier, which implies that the formation of benzopyran is not favored in the presence of CsF. However, the abstraction of the α-hydrogen atom in Int1-CsF with CsF shows a very low free energy barrier and is the most favored pathway for aryl propargyl ether Claisen rearrangement in the presence of CsF to form benzofuran. In the case of substituted aryl propargyl ethers, a methoxy group on the benzene ring lowers the activation barrier. The HOMO–LUMO, conformational and NBO analysis indicate that increasing methyl substitution on the propargyl residue enhances the rearrangement reaction.

Synthesis of 2-Benzylphenyl Ketones by Aryne Insertion into Unactivated C-C Bonds.

A transition-metal-free procedure to access to functionalized 2-benzylphenyl ketones is described by direct insertion of arynes into benzylic C-C bonds. This reaction was promoted by cesium fluoride at room temperature, allowing the products to form in high selectivity and achieve good functional group tolerance.

Carbonylative Hiyama coupling of aryl halides with arylsilanes under balloon pressure of CO

An efficient protocol has been developed for the carbonylative Hiyama coupling of aryl halides using the cesium fluoride as a promoter by palladium-catalyzed in NMP. This protocol was applied to a wide variety of functionalized and hindered aryl iodides and bromides with arylsilanes, to afford the desired biaryl ketones in good to excellent yields.

ChemInform Abstract: A Cesium Fluoride Promoted Efficient and Rapid Multicomponent Synthesis of Functionalized 2‐Amino‐3‐cyano‐4H‐pyran and Spirooxindole Derivatives.

Abstract A rapid, one-pot and highly efficient protocol for the synthesis of pharmaceutically interesting functionalized 2-amino-3-cyano-4 H -pyran and spirooxindole derivatives has been developed using commercially available CsF as a catalyst in the reaction of malononitrile and aryl aldehydes or isatins with 1,3-cyclohexanediones. The major advantages of this methodology are excellent yield at ambient temperature, very short reaction time (5–10 min), and use of an inexpensive catalyst.

Palladium-Catalyzed Regioselective Arylation of Pyrazolo[1,5-a]pyridines via C–H Activation and Synthetic Applications on P38 Kinase Inhibitors

A direct arylation of pyrazolo[1,5-a]pyridines with aryl iodides selectively occurring at the C-3 and C-7 positions via palladium-catalyzed C–H activation is described. In these reactions, (a) cesium(I) fluoride and (b) silver(I) carbonate were employed as the additive to afford 3- and 7-arylated pyrazolo[1,5-a]pyridines, respectively, in modest to good yields. These reactions showed good compatibility with functional groups, and the catalytic mechanisms of these reactions were proposed. Finally, the synthetic application on the potent p38 kinase inhibitors was demonstrated.

Palladium–Silver Cooperativity in an Aryl Amination Reaction through C–H Functionalization

The mechanism of palladium-acetate-catalyzed ortho-amination of N-arylbenzamides by using O-benzoyl hydroxylpiperidine [PhCOON(C5H10)] has been examined by using DFT(M06, B3LYP) computational methods. Particular emphasis is placed on the role of additives such as cesium fluoride and silver acetate. The lowest-energy pathway has been identified by carefully examining 15 or more configurationally different possibilities in each important step of the reaction. The key mechanistic events include (i) the aryl C–H activation of the substrate through a cyclometalation deprotonation; (ii) N–O activation of the reactant PhCOONR2 (where −NR2 = pypiridyl); and (iii) reductive elimination wherein the −N(C5H10) substituent gets transferred to the substrate. A heterobimetallic active species [Pd(μ-OAc)3Ag] is identified as catalytically superior over the conventionally proposed monometallic palladium acetate. A cooperative interaction between Pd(II) and Ag(I) is found to offer additional stabilization to the transition...

Lab-on-chip based optical biosensors for the application of dental fluorosis

Optical biosensors are powerful detection and analysis tool that has vast applications in biomedical research, healthcare, pharmaceuticals, environmental monitoring, and the battlefield. Biosensors consist of a biological entity that can be an enzyme, antibody, or nucleic acid that interacts with an analyte and produces the signal that is measured electronically. A variety of substances including nucleic acids, proteins (particularly antibodies and enzymes), lectins (plant proteins that bind sugar moieties) and complex materials (organelles, tissue slices, microorganism), can be used as the biological components. Fluoride content in drinkable groundwater directly affects the quality of drinking water. In this paper we have demonstrated a 2-dimensional photonic crystal based biosensor with line defect which can detect different fluorides in water. Simulation and analysis has been done for calcium fluoride, cesium fluoride, potassium fluoride, lithium fluoride and strontium fluoride and peak has been observed. One such major detection is to detect dental fluorosis caused by the fluorides present in water. Finite Difference Time Domain (FDTD) method has been used for the analysis. MEEP is Maxwell's Electromagnetic Equation Propagation simulation tool. The application of FDTD method is computation of transmission spectrum. MEEP is simulation package for the computation of transmission/reflection spectra, field patterns, resonant modes & frequencies in dielectric structures.

ITO-free large-area top-emission organic light-emitting diode by blade coating

Large-area top-emitting organic light-emitting diodes (TEOLEDs) with multi-layer structure are successfully demonstrated using the solution-processable blade coating on ITO-free substrate. The semitransparent cathode of TEOLED is composed of lithium fluoride (LiF), aluminum (Al) and silver (Ag). The composition of 3nm Al and 10nm Ag has a transmittance of 56% and a sheet resistance of 11Ω/□. It is applied to the green phosphorescence device with an emissive area of 2cm by 2.5cm. The maximum current efficiency is 25.2cd/A with high light-emission uniformity within 10% variation. The large-area TEOLEDs show comparable current efficiency as the small-area devices with an emissive area of 2mm by 2mm (having the same device structure) and better efficiency than traditional large-area bottom-emitting devices. Cesium fluoride (CsF) and n-doped electron transport layer are applied to improve electron injection. At 6V, the luminance is raised from 141cd/m2 to 502cd/m2 and 304cd/m2, respectively. In n-doped device, a simple Al/Ag cathode is used without LiF.

Enhancement in performance of polymer solar cells by introducing solution-processed dipole interlayer

Metal fluorides (e.g., LiF and BaF2) are usually introduced as an electron transport layer in conventional polymer solar cells (PSCs). However, because they are insoluble, vacuum deposition is inevitable, resulting in a high process cost and the difficulty of introduction in PSCs. In this study, we fabricated inverted PSCs with a double interlayer by using solution-processable cesium fluoride and ZnO to improve the electron extraction. The power conversion efficiency was enhanced from 7.5% to 8.2% by a 9.3% increase in the fill factor. In addition, we demonstrated the enhancement of the FF by atomic force microscopy, space charge limited current, and photoluminescence.

Novel indotricarbocyanine dyes covalently bonded to polyethylene glycol for theranostics

Abstract The synthesis methods for the indotricarbocyanine dyes covalently bonded to polyethylene glycols with varying degrees of polymerization have been developed. New indotricarbocyanine was synthesized in one step using the Mukayama reagent in polyethylene glycol with cesium fluoride as a basic catalyst. In vivo investigation of the phototherapeutic dye activity has shown selective recognition of malignant tissues, where accumulation of the dye was 4–5 times higher than in normal tissues. The necrotic area after local photoirradiation at the effective energy fluence 180 J/cm 2 , λ = 780 nm was observed to a depth of 2.5 cm making the synthesized dyes very promising for further pharmaceutic research.

Facile preparation of 3-substituted-2,6-difluoropyridines: application to the synthesis of 2,3,6-trisubstituted pyridines

We report a facile method for the difluorination of 3-substituted-2,6-dichloropyridines using cesium fluoride as a fluorination reagent in dimethyl sulfoxide. It is proposed that this method for preparing 3-substituted-2,6-difluoropyridines is simpler and easier than those reported in previous literature. To examine the utility of 3-substituted-2,6-difluoropyridines in synthetic chemistry, we also demonstrate a subsequent conversion to 2,3,6-trisubstituted pyridines by a tandem nucleophilic aromatic substitution.

Synthesis and photophysical properties of novel multisubstituted benzene and naphthalene derivatives with high 2D-π-conjugation

A new small molecule, with D-A-D framework was prepared in good yield by using a [2+1+2+1] cycloaddition followed by the [4+2] Diels–Alders reaction. Additionally, tetra-substituted naphthalene derivatives were also prepared from in situ generated benzyne (using 2-trimethylsilylphenyl triflate and cesium fluoride). All of this compounds exhibit strong 2D-π-conjugation. The influence of this type of interactions on photophysical properties with the aid of DFT calculations was examined. The preliminary tests of application possibility of synthesized compounds in devices for optoelectronics were carried out as well.

Cesium Salts in Organic Synthesis: A Review

The excellent advantages of cesium such as short reaction times, small amount of reagent used, high yields of the products, milder reaction conditions, and easy work-up procedures counter balanced its higher cost. From the last two decades, the use of cesium salts has received an increasing interest in numerous varieties of synthetic conversions. Today, the use of cesium salts has reached the industrial acceptance. For example, palladium catalyzed coupling reactions like the Suzuki coupling or the Buchwald amination reactions use the cesium salts. However, cesium salts are also utilized in direct nucleophilic substitution reactions since they have replaced the standard bases. This is the first review in this area which exclusively deals with recent developments in Cs salt promoted reactions with special focus on mechanistic aspects as well as on the recent applications in drug synthesis. Today, cesium carbonate (Cs2CO3), cesium fluoride (CsF), cesium acetate (CsOAc) and cesium hydroxide monohydrate (CsOH·H2O) are the most frequently used cesium compounds in the organic synthesis. Keywords: Cesium salts, CsF, CsOH, Cs2CO3, CsOAc, organic synthesis and applications.

A cesium fluoride promoted efficient and rapid multicomponent synthesis of functionalized 2-amino-3-cyano-4H-pyran and spirooxindole derivatives

Abstract A rapid, one-pot and highly efficient protocol for the synthesis of pharmaceutically interesting functionalized 2-amino-3-cyano-4 H -pyran and spirooxindole derivatives has been developed using commercially available CsF as a catalyst in the reaction of malononitrile and aryl aldehydes or isatins with 1,3-cyclohexanediones. The major advantages of this methodology are excellent yield at ambient temperature, very short reaction time (5–10 min), and use of an inexpensive catalyst.

Nucleophilic addition of (difluoromethyl)trimethylsilane to selected α-imino ketones and aryl diketones

Chemoselective addition of (difluoromethyl)trimethylsilane (CHF2SiMe3) to the carbonyl bond of aryl glyoxal derived α-imino ketones, and selected diaryl 1,2-diketones were studied in the presence of initiators, such as potassium tert-butoxide or caesium fluoride. Subsequent reduction of the obtained α-imino alcohols and α-hydroxy ketones with sodium borohydride gave the expected 2-amino 1-(difluoromethyl)alcohols and (difluoromethyl)-1,2-diols respectively in moderate to good yields. High de values were observed for the reduction of α-(difluoromethyl)-α-hydroxy ketones.

Silver‐Mediated Oxidative Fluorotrifluoromethylation of Unactivated Alkenes

AbstractAn efficient regioselective fluorotrifluoromethylation of unactivated alkenes has been developed. The reaction of alkenes with (trifluoromethyl)trimethylsilane (TMSCF3) and Selectfluor in the presence of silver trifluoromethanesulfonate (AgOTf), cesium fluoride (CsF), and iodobenzene diacetate [PhI(OAc)2] in N,N‐dimethylformamide (DMF) at −20 °C gave the corresponding fluorotrifluoromethylated products in moderate to good yields. The silver salt turns out to be crucial for this transformation.magnified image

Structure and properties of molecular and ionic clusters in vapour over caesium fluoride

The properties of neutral molecules Cs2F2, Cs3F3, and Cs4F4, and positive and negative cluster ions Cs2F+, CsF2−, Cs3F2+, Cs2F3−, Cs4F3+, and Cs5F4+ were studied by several of quantum chemical methods implementing density function theory and Möller–Plesset perturbation theory of second and fourth orders. For all species, the equilibrium geometrical structure and vibrational spectra were determined. Different isomers have been revealed for the trimer neutral molecule Cs3F3; pentaatomic, both positive and negative, Cs3F2+, Cs2F3−; and heptaatomic Cs4F3+ ions. The most abundant isomers in the saturated vapour were determined. Enthalpies of dissociation reactions and enthalpies of formation of the species were obtained.

Rapid cesium fluoride-catalyzed Knoevenagel condensation for the synthesis of highly functionalized 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol) derivatives

A rapid, convenient, and environmentally friendly protocol was developed for the synthesis of functionalized 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) via a tandem Knoevenagel–Michael reaction by condensing pyrazolone with readily available differently substituted aldehydes and catalyzed by cesium fluoride at room temperature.

Fluoride-promoted esterification with imidazolide-activated compounds: a modular and sustainable approach to dendrimers.

Based on the growing demand for facile and sustainable synthetic methods to structurally perfect polymers, we herein describe a significant improvement of esterification reactions capitalizing on 1,1'-carbonyldiimidazole (CDI). Cesium fluoride was shown to be an essential catalyst for these reactions to reach completion. This approach was successfully applied to the synthesis of structurally flawless and highly functional polyester dendrimers employing traditional and accelerated growth strategies. A sixth generation bis-MPA dendrimer with a molecular weight of 22.080 Da and 192 peripheral hydroxy groups was isolated in less than one day of total reaction time. Large quantities of dendrimers were obtained in high yields (>90%) using simple purification steps under sustainable conditions. The fluoride-promoted esterification (FPE) via imidazolide-activated compounds is wide in scope and constitutes a potentially new approach toward functional polymers and other materials.

Fluoride‐Promoted Esterification with Imidazolide‐Activated Compounds: A Modular and Sustainable Approach to Dendrimers

AbstractBased on the growing demand for facile and sustainable synthetic methods to structurally perfect polymers, we herein describe a significant improvement of esterification reactions capitalizing on 1,1′‐carbonyldiimidazole (CDI). Cesium fluoride was shown to be an essential catalyst for these reactions to reach completion. This approach was successfully applied to the synthesis of structurally flawless and highly functional polyester dendrimers employing traditional and accelerated growth strategies. A sixth generation bis‐MPA dendrimer with a molecular weight of 22.080 Da and 192 peripheral hydroxy groups was isolated in less than one day of total reaction time. Large quantities of dendrimerswere obtained in high yields (>90 %) using simple purification steps under sustainable conditions. The fluoride‐promoted esterification (FPE) via imidazolide‐activated compounds is wide in scope and constitutes a potentially new approach toward functional polymers and other materials.