Presence Of Tetrabutylammonium Fluoride Research Articles

Electrogenerated acetonitrile anions/tetrabutylammonium cations: an effective catalytic system for the synthesis of novel chromeno[3′,4′:5,6]pyrano[2,3-d]pyrimidines

An efficient and convenient synthesis of novel chromeno[3′,4′:5,6]pyrano[2,3-d]pyrimidines is described, using the electrogenerated anion of acetonitrile as the base in the presence of tetrabutylammonium fluoride as an effective supporting electrolyte in a one-pot, three-component condensation of barbituric acid, an aromatic aldehyde or isatin, and 4-hydroxycoumarin. The reaction is carried out in an undivided cell containing an iron electrode as the cathode and a Pt electrode as the anode, at a constant current at room temperature.

Synthesis, characterization, structural analysis of metal(II) complexes of N′-[(E)-3-Bromo-5-Chloro-2-hydroxybenzidene]-4-hydroxybenzohydrazide—Multisubstituted Schiff base as a F− and Cu2+ ions selective chemosensor

New colorimetric chemosensor, N′-[(E)-3-Bromo-5-Chloro-2-hydroxybenzidene]-4-hydroxybenzohydrazide, containing OH and NH groups as binding sites have been synthesized and characterized by spectral UV, IR, NMR and ESR. The molecular structure of ligand is determined by X-ray crystallography and it has the monoclinic space group P21/c with cell parameters a=15.1058(6), b=14.3433(6), c=17.5800(8)Å and Z=8. The electronic spectral measurements show that Co2+, Ni2+ and Zn2+ complexes have tetrahedral geometry, while Cu2+ complex has square planar geometry. Magnetic measurements show that Cu2+, Co2+ and Ni2+ complexes have paramagnetic behavior and Zn2+ complex has diamagnetic behavior. Anion binding studies carried out using 1H NMR and UV–visible spectrophotometric titrations revealed that these receptors exhibit selective recognition towards F− over other halide anions. The selectivity for F− among the halides is attributed mainly to the hydrogen-bond interaction of the receptor with F−. Receptor (5×10−5M) shows color change from colorless to yellow in the presence of tetrabutylammonium fluoride (TBAF, 1.5×10−3M). Moreover, F−-induced color changes remain the same even in the presence of large excess of Cl−, Br− and I−. The binding constant is found to be higher towards F− ion and this may be due to presence of OH group, which offers extra binding site. Chromogenic receptor undergoes distinct color changes from colorless to green on gradual addition of Cu2+ can be used as colorimetric probes for spectrophotometric and visual analysis of Cu2+ in the presence of other transition metal ions such as Co2+, Ni2+ and Zn2+.

2-Chlorotetrafluoroethanesulfinamide induced asymmetric vinylogous Mannich reaction

The generality of (S)-2-chlorotetrafluoroethanesulfinamide (CTFSA) induced asymmetric vinylogous Mannich (AVM) addition reaction has been investigated. The reaction of aldimines derived from (S)-CTFSA with 2-(tert-butyldimethylsilyloxy) furan (TBSOF) took place regioselectively at the γ-site at room temperature in DMSO under air atmosphere to give the desired addition products in syn-configuration with high diastereoselectivities (up to 98:2 dr). However, anti-configuration product as major isomer was obtained in the presence of tetra-butyl ammonium fluoride (TBAF) at −78 °C. Facile removal of the auxiliary group without epimerization demonstrated their synthetic potential for piperidone derivatives.

Synthesis of a new colorimetric receptor based on calix[4]pyrrole binding oxime for selective recognition of fluoride ions

A colorimetric anion sensor α-meso-heptaethylcalix[4]pyrrole-meso-3-aminophenyl-p-nitrobenzaldoxime was synthesised and characterised by various spectroscopic techniques. Anion-binding studies were carried out using UV–vis, and 1H NMR titrations, revealing that the receptor exhibits selective recognition towards F− over other anions. The selectivity for F− among the halides is attributed mainly to the hydrogen bond interaction of the receptor with F− . Receptor showed colour change from colourless to yellow in the presence of tetrabutylammonium fluoride with 1:2 stoichiometry. Cyclic voltammetry studies, carried out in CH3CN, provided evidence of an anion-dependent electrochemical response with F− ion. This response was particularly dramatic in the case of receptor after the addition of ∼1 equiv. of F− ion.

Synthesis and in vitro cellular uptake of 11C-labeled 5-aminolevulinic acid derivative to estimate the induced cellular accumulation of protoporphyrin IX

Protoporphyrin IX (PpIX) accumulation induced by exogenous 5-aminolevulinic acid (ALA) in tumors affects the therapeutic efficacy of ALA-based photodynamic and sonodynamic therapies. To develop a new imaging probe to estimate the ALA-induced PpIX accumulation, 11C-labeled ALA analog (4), an ALA-dehydratase inhibitor, was radiosynthesized via 11C-methylation of a Schiff-base-activated precursor in the presence of tetrabutylammonium fluoride, followed by the hydrolysis of ester and imine groups. The cellular uptake of 4 linearly increased with time and was inhibited by ALA and other transporter competitors. Monitoring analog 4 with positron emission tomography might be useful to estimate the ALA-induced PpIX accumulation in tumors.

Novel vic-dioxime ligand containing calix[4]pyrrole moiety: synthesis, characterization, anion binding studies and complexation with Ni(II)

A new vic-dioxime functionalized calix[4]pyrrole was synthesized from anti-chloroglyoxime and 4-aminophenyl-calix[4]pyrrole at room temperature. The Ni(II) complex has been prepared by reacting the ligand with NiCl2·6H2O in ethanol. These receptors were characterized by elemental analyses, 1H and 13C NMR spectra, IR and mass spectra. Electrochemical properties of the ligand, and its Ni(II) complex were investigated in CH2Cl2 solution by cyclic voltammetry at 100 mV s−1 scan rate. Anion-binding studies were carried out using UV–Vis, and 1H NMR titrations, revealed that the Ni(II) complex exhibits selective recognition toward F− over other anions. The selectivity for F– among the halides is attributed mainly to the hydrogen-bond interaction of the receptor with F–. Receptor showed colour change from red to brown in the presence of tetrabutylammonium fluoride (TBAF) with 1:2 stoichiometry.

An efficient synthesis of hemiaminal of indoles by using tetrabutylammonium fluoride (TBAF) in water as a reusable reaction media

The synthesis of hemiaminal of indole is described by the reaction of indole with formaldehyde in the presence of TBAF in water at ambient temperature. The procedure is very efficient, mild, convenient, and environmentally benign with high yield of product. Moreover, the reuse of reaction media makes the procedure an attractive alternative to earlier methods.

Fluorescent Chemosensing Properties of New Isoindoline Based-Receptors towards F<sup>-</sup> and Cu<sup>2+</sup> Ions

Two simple colorimetric and fluorescent anion chemosensors based on amide moieties, 4-nitro-N-[(1,3-dioxoisoindolin-2yl)benzamide (1), 3,5-dinitro-N-[(1,3-dioxoisoindolin-2yl)benzamide (2) have been synthesized and characterized. Comparing with other anions studied, the UV-visible absorption spectrum in DMSO shows significant response toward F- ion with high selectivity, and meanwhile color change is observed from colorless to pink and violet for 1 and 2 respectively in the presence of tetrabutylammonium fluoride (TBAF) (5 × 10-3 M). Moreover, F--induced color changes remain the same even in the large excess of Cl- , Br- and I-. In addition, the 1H NMR spectrum titration in DMSO-d6 shows deprotonation of the receptors 1 and 2 in the presence of basic F- ion. In particular, addition of F- to the receptors 1 and 2 resulted in an enhancement in fluorescence intensity at 770 nm. Both receptors 1 and 2 exhibit a fluorescent emission enhancement when addition of Zn2+, Ni2+, Co2+, Cu2+ and Mn2+ metal ions. The fluorescent enhancement values for the receptor 1 are 2.29 (Cu2+), 1.85 (Ni2+), 1.37 (Co2+), 1.27 (Mn2+), 1.25 (Zn2+) and for 2, 2.57 (Cu2+), 1.66 (Ni2+), 1.36 (Co2+), 1.15 (Mn2+), 1.09 (Zn2+). The selectivity of Cu2+ is higher for 1 and 2 than other metal ions such as Zn2+, Ni2+, Co2+ and Mn2+.

Synthesis of Conjugated Aryleneethynylenesiloles Dendron

AbstractThree routes were designed to synthesize a π‐conjugated aryleneethynylenesiloles dendron. With the desilylation of the disilole mono(silylethynyl) derivative in the presence of potassium carbonate (K2CO3), the silole‐containing oligomer has been successfully synthesized without impact on the Si‐(CH3)2 group. The disilole mono(silylethynyl) derivative was prepared by means of the Sonogashira heterocoupling reaction between the diacetylene compound and asymmetrical silole, catalyzed by the dichloro bis(triphenylphosphine)palladium, in a divergent synthesis. Due to their steric effect and triethynylbenzene self‐coupling Glaser reaction, the endeavour to prepare the dendron by controlling the molar ratio of asymmetrical silole and 1,3,5‐triethynylbenzene was failed. The another attempt to prepare the dendron by different desilylation condition of triisopropylsilyl group and trimethylsilyl group was also failed, the desilylation of Si‐(CH3)2 group in silacyclopentadiene unit was also easily accomplished in the presence of tetrabutylammonium fluoride(Bu4NF), whereas no reaction occurred when K2CO3 was used instead of Bu4NF.

Novel thiophene based colorimetric and fluorescent receptor for selective recognition of fluoride ions

A colorimetric anion sensor 2,2′-(1E,1′E)-(thiophene-2,5-diylbis(methan-1-yl-1-ylidene)) was synthesized and characterized by various spectroscopic techniques. Anion binding studies were carried out using UV–visible spectrophotometric titrations and emission spectra studies, revealed that the receptor exhibits selective recognition toward F−over other anions. The selectivity for F−among the halides is attributed mainly to the hydrogen-bond interaction of the receptor with F−. Receptor 1 showed color change from fluorescent green to orange in the presence of tetrabutylammonium fluoride with 1:1 stoichiometry. Receptor 1 exhibits remarkably enhanced fluorescence intensity.

Major increases of the reactivity and selectivity in aminoglycoside O-alkylation due to the presence of fluoride ions

Major increases of the selectivity and/or reactivity in aminosugar and sugar O-alkylation were observed in the presence of tetrabutylammonium fluoride (TBAF) in comparison to TBAI under phase-transfer conditions or in solution. The presence of TBAF allowed the selective and rapid alkylation of the 6-hydroxyl function of neamine and efficient preparation of protected intermediates useful in synthesis and potent or potential antimicrobial O-alkylated derivatives of neamine and paromamine. In regard to the observed strong effects of TBAF, the alkylation and acylation of carbohydrates merit to be studied in the presence of TBAF under phase-transfer conditions.

Diastereoselective Three‐Step Route to o‐(6‐Nitrocyclohex‐3‐en‐1‐yl)phenol and Tetrahydro‐6H‐benzo[c]chromen‐6‐ol Derivatives from Salicylaldehydes

AbstractThis work was aimed at preparing o‐(6′‐nitrocyclohex‐3′‐en‐1′‐yl)phenol and tetrahydro‐6H‐benzo[c]chromen‐6‐ol derivatives in three steps starting from salicylaldehydes. Initially 3‐acetylcoumarins were prepared in the absence of solvent using a solid base catalyst such as PS‐TBD. In the second step, the Diels–Alder reactions of 3‐nitrocoumarins and 3‐acetylcoumarins under thermal conditions or in the presence of hafnium chloride yielded the corresponding tetrahydrobenzo[c]chromenones. The final part of the work was dedicated to the transformation of nitro‐tetrahydrobenzo[c]chromenones into o‐(6′‐nitrocyclohex‐3′‐en‐1′‐yl)phenol derivatives in aqueous medium and to the conversion of acetyl tetrahydrobenzo[c]chromenones into the corresponding tetrahydro‐6H‐benzo[c]chromen‐6‐ol derivatives in tetrahydrofuran (THF), in the presence of tetrabutylammonium fluoride (TBAF) on silica. In every case the diastereoselectivity was complete and the reaction yields were high.

Synthesis of macrocyclic molecular brushes with amphiphilic block copolymers as side chains

AbstractMacrocyclic molecular brushes c‐PHEMA‐g‐(PS‐b‐PEO) consisting of macrocyclic poly(2‐hydroxylethyl methacrylate) (c‐PHEMA) as backbone and polystyrene‐b‐poly(ethylene oxide) (PS‐b‐PEO) amphiphilic block copolymers as side chains were synthesized by the combination of atom transfer radical polymerization (ATRP), click chemistry, and single‐electron transfer nitroxide radical coupling (SET‐NRC). First, a linear α‐alkyne‐ω‐azido heterodifunctional PHEMA (l‐HCC‐PHEMA‐N3) was prepared by ATRP of HEMA using 3‐(trimethylsilyl)propargyl 2‐bromoisobutyrate as initiator, and then chlorine end groups were transformed to N3 group by nucleophilic substitution reaction in DMF in the presence of an excess of NaN3. The 3‐trimethylsilyl groups could be removed in the presence of tetrabutylammonium fluoride, and the product was cyclized by “click” chemistry in high dilution conditions. The hydroxyl groups on c‐PHEMA were transferred into bromine groups by esterification with 2‐bromoisobutyryl bromide and then initiate the ATRP of styrene. The formed macrocyclic molecular brushes c‐PHEMA‐g‐PS were coupled with the TEMPO‐PEO to afford the target macrocyclic molecular brushes c‐PHEMA‐g‐(PS‐b‐PEO) by SET‐NRC, and the efficiency is as high as 80∼85%. All of the intermediates and final product were characterized with 1H NMR, Fourier transform infrared (FTIR), and gel permeation chromatography in details © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Fluoride-Promoted Cross-Coupling of Chloro(mono-, di-, or triphenyl)germanes with Aryl Halides in “Moist” Toluene. Multiple Transfer of the Phenyl Group from Organogermane Substrates and Comparison of the Coupling Efficiencies of Chloro(phenyl)germanes with their Corresponding Stannane and Silane Counterparts

The trichlorophenyl-, dichlorodiphenyl-, and chlorotriphenylgermanes undergo Pd-catalyzed cross-couplings with aryl bromides and iodides in the presence of tetrabutylammonium fluoride in toluene with addition of the measured amount of water. One chloride ligand on the Ge center allows efficient activation by fluoride to promote transfer of one, two, or three phenyl groups from the organogermanes. The corresponding chlorophenylstannanes were found to be more reactive than chlorophenylsilanes, which in turn were more effective than chlorophenylgermanes. One chloride ligand on the Ge or Si center allows efficient activation by fluoride to promote transfer of up to three aryl groups from germane or silicon. However, no haloligand was necessary to be present on the Sn center, since tetraphenyltin efficiently transferred up to four phenyl groups during fluoride-promoted couplings with aryl halides. (19)F NMR studies suggested formation of the fluorophenylgermanes and the hypervalent germanate species as possible intermediates.

ChemInform Abstract: Synthesis of Trifluoromethyl Analogue of L-Fucose and 6-Deoxy-D- altrose.

Trifluoromethylation of the acyclic derivative of D-lyxose, 3, with trifluoromethyltrimethylsilane in the presence of tetrabutylammonium fluoride yielded a mixture of trifluoromethyl adducts, 5a and b, which was converted to 6,6,6-trifluoro-L-fucose 9a and 6-deoxy-6,6,6-trifluoro-D-altrose 9bvia selective oxidation of the primary hydroxy group involving treatment of the trimethylsiloxy derivatives, 7a and b, with Collins reagent.

ChemInform Abstract: Highly Stereospecific, Palladium-Catalyzed Cross-Coupling of Alkenylsilanols.

Alkenylsilanols bearing methyl ((E)-1 and (Z)-1) or isopropyl ((E)-2 and (Z)-2)) substituents are converted to disubstituted alkenes by a palladium(0)-catalyzed cross-coupling reaction with aryl or vinyl iodides in the presence of tetrabutylammonium fluoride or hydroxide. Yields and stereoselectivities are generally high, and the reaction is compatible with a wide range of functional groups.

Palladium-Catalyzed Cross-Coupling of 2,3-Naphthoxadisilole with Aryl Halides

Palladium-catalyzed cross-coupling between 2,3-naphthoxadisilole and aryl halides in the presence of tetrabutylammonium fluoride afforded 2-aryl naphthalenes. This is first report that oxadisilole served as a partner in the palladium-catalyzed cross-coupling reactions. The reaction mechanism was also studied.

A Serendipitous C−C Bond Formation Reaction between Michael Donors and Diiminoquinoid Ring Assisted by Quaternary Ammonium Fluoride

An efficient C-C bond formation reaction assisted by a fluoride ion has been identified for N,N'-diphenyl-1,4-phenylenediimine with the compounds having an active methylene group. The reaction follows the typical Michael addition fashion and proceeds to completion within 1 h at 70 degrees C in acetonitrile in the presence of tetrabutylammonium fluoride (TBAF), while the same reaction failed to proceed in the absence of a fluoride anion. The new finding reported herein also offers an unprecedented method for a direct functionalization of polyaniline backbone with versatile functional alkyl groups.

β-Nitroacrylates and silyl enol ethers as key starting materials for the synthesis of polyfunctionalized β-nitro esters and 1,2-oxazine-2-oxides

The reaction of silyl enol ethers with β-nitroacrylates, in the presence of tetrabutyl ammonium fluoride as catalyst, allows the formation of polyfunctionalized β-nitro esters, or hexahydro-4 H-benzoxazine-2-oxides, depending on the nature of the starting silyl enol ethers.

SYNTHESIS AND CHARACTERIZATION OF POLY{4-[2-(tert-BUTYLDIMETHYLSILOXY)ETHYL]STYRENE} AND ITS HYDROLYSIS DERIVATIVE

The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at –80°C. The initiator 1,1-diphenylethylene (DPE) capped 2-chloro-2,4,4-trimethylpentane (TMPCl) was formed in situ in conjunction with titanium tetrachloride (TiCl4). The Lewis acidity of TiCl4 was decreased by the addition of titanium(IV) isopropoxide (Ti(OiPr)4) to accomplish living polymerization of TBDMES. Hydrolysis of poly(TBDMES) in the presence of tetra-butylammonium fluoride yielded poly[4-(2-hydroxyethyl)styrene] (poly(HOES)). FT-IR, NMR and DSC demonstrated the hydrolysis was complete.