Presence Of Boron Trifluoride Etherate Research Articles

An Efficient Combinatorial Synthesis of Novel Thiazolidinone‐Bis Schiff Base Hybrids Using One‐Pot Multicomponent Reaction

AbstractA facile multicomponent synthesis of novel thiazolidinone‐bis Schiff base hybrids has been developed using readily available starting materials. The four‐component reaction of isothiocyanate, hydrazine, aldehyde and α‐bromoester in water readily affords thiazolidinone‐bis Schiff base hybrids, whereas the five‐component strategy involving the same reactants in the presence of boron trifluoride etherate in acetonitrile leads to the formation of the fully functionalized thiazolidinone‐bis Schiff base hybrids.

Selective 5‐Exo‐Dig versus 6‐Endo‐Dig Cyclization of Benzoimidazole Thiols with Propargyl Alcohols

AbstractWe describe here the Lewis acid‐promoted cyclization reaction of benzomidazole thiols with propargyl alcohols for the selective synthesis of benzoimidazolo thiazines and benzothiazolo imidazoles. The reaction is regioselective and the solvent controls the formation of products. The systematic study to determine the best reaction conditions revealed that the six‐membered benzoimidazolo thiazines were obtained by reacting the benzoimidazole thiols with propargyl alcohols in the presence of boron trifluoride etherate, using dichloromethane as the solvent. Replacement of dichloromethane with dimethylformamide, by using the same starting material and reagents, gave selectively the five‐membered benzothiazolo imidazoles. The mechanism of this cyclization was proposed based on the results obtained and several control experiments.magnified image

Rational Design 2-Hydroxypropylphosphonium Salts as Cancer Cell Mitochondria-Targeted Vectors: Synthesis, Structure, and Biological Properties.

It has been shown for a wide range of epoxy compounds that their interaction with triphenylphosphonium triflate occurs with a high chemoselectivity and leads to the formation of (2-hydroxypropyl)triphenylphosphonium triflates 3 substituted in the 3-position with an alkoxy, alkylcarboxyl group, or halogen, which were isolated in a high yield. Using the methodology for the disclosure of epichlorohydrin with alcohols in the presence of boron trifluoride etherate, followed by the substitution of iodine for chlorine and treatment with triphenylphosphine, 2-hydroxypropyltriphenylphosphonium iodides 4 were also obtained. The molecular and supramolecular structure of the obtained phosphonium salts was established, and their high antitumor activity was revealed in relation to duodenal adenocarcinoma. The formation of liposomal systems based on phosphonium salt 3 and L-α-phosphatidylcholine (PC) was employed for improving the bioavailability and reducing the toxicity. They were produced by the thin film rehydration method and exhibited cytotoxic properties. This rational design of phosphonium salts 3 and 4 has promising potential of new vectors for targeted delivery into mitochondria of tumor cells.

Manganacarborane based on 5,6-dicarba-nido-decaborane with triphenylphosphine at boron atom

In the reaction of the ionic complex of manganese based on 5,6-dicarba-nido-decaborane [1,1,1-(CO)3-isonido-1,2,4-MnC2B8H10]- tmdaH± (1) (tmdaH+- protonated form of N,N,N′,N′-tetramethyl-1,8-diaminonaphthalene) with triphenylphosphine (PPh3) in the presence of boron trifluoride etherate (BF3⋅Et2O) in benzene, the neutral complex 1,1,1-(CO)3–7-PPh3-isonido-1,2,4-MnC2B8H9 (2) was isolated as one of the main products. The position of the PPh3 substituent in the carborane ligand was established by 1H, 11B, 31P, 13C, [11B−11B]-COSY, 1H{11B} NMR spectroscopy methods and confirmed by X-ray diffraction analysis.

Synthesis, characterization, and curing of propylene oxide and glycidyl nitrate random copolymer (GN-ran-PO) and investigation of its compatibility with different energetic plasticizers

In this research, arandom copolymer of propylene oxide and glycidyl nitrate (poly [GN-ran-PO]) (Mn = 1152 g.mol−1) was synthesized via ring-opening polymerization of epoxides in the presence of boron trifluoride etherate (BF3.OEt2) as the catalyst. This copolymer has a potential use as a binder in the propellant industries. The obtained product has characterized by 1H and 13C NMR spectroscopy, FTIR, and gel permeation chromatography (GPC). The thermal behavior of the random copolymer was determined by differential scanning calorimetry (DSC). Energetic polyurethane was synthesized by curing of the random copolymer with different curing agents such as toluene-2,4-diisocyanate(TDI), isophorone diisocyanate(IPDI), desmodurN100, (IPDI/N100) and different NCO/OH ratios. To evaluate the plasticizing effect of the different plasticizers on the thermo-mechanical properties of the polyurethane, the compatibility of the copolymer with three energetic plasticizersincludingn‐butyl nitroxyethyl nitramine (BuNENA), trimethylol ethane trinitrate (TMETN), and 1,2,4-butanetriol trinitrate (BTTN) has studied using the solubility parameter, rheological and thermal analysis. The solubility parameter differences indicate that the BuNENA has better miscibility with this copolymer than others. This plasticizer reduced the glass transition temperature of its composition with copolymer from -47 °C to -58 °C. Moreover, the rheological analysis also confirms that BuNENA is more compatible with the copolymer. The mechanical properties effect of the BuNENA plasticizer on the polyurethane network has investigated using dynamic mechanical analysis (DMA) as well as the tensile test. The IPDI/N100 curing agents-polyurethane mixture, demonstrate appropriate mechanical properties (0.6 MPa stress and 109% elongation) that make it a suitable binder system comparison with pure PGN (unstable and de-cured). Also, the mechanical properties of the prepared polyurethane containing 20 wt.% BuNENA showed 0.42 MPa stress and 124% elongation.

Phosphorus-containing star-shaped polymer conjugates for biomedical applications

A novel phosphorus-containing biocompatible and biodegradable star-shaped polymer was designed as a precursor polymer for obtaining sugar or drug conjugates. The star polymer bearing three arms was synthesized applying the “coupling on” approach. Linear oligo(oxyethylene H-phosphonate) with a terminal hydroxyl group was prepared and used as functional arms able to react with tris(2,3-epoxypropyl) isocyanurate as core in the presence of boron trifluoride etherate as catalyst. The H-phosphonate moieties in the arm chains were transformed into trimethylsilyl phosphite groups and further via Staudinger reaction they were converted into phosphoramidates bearing specific residues. When the Staudinger reaction was carried out with a glucose-containing azide, i.e. 2-p-azidobenzamide-2-deoxy-1,3,4,6-tetra-O-trimethylsilyl-alpha-D-glucopyranose, the product was a star-shaped glycopolymer. The conjugation of AZT yielded a star-shaped polymer-drug conjugate. Multinuclear NMR spectroscopy was applied as a powerful tool for determination of the conversion and structure of the reaction products. Analytical ultracentrifugation, dynamic and electrophoretic light scattering techniques were used for characterization of the star polymers and conjugates, as well as in binding studies with Concanavalin A. Drug release measurements and cytotoxicity tests were also performed. The obtained results evidenced feasible synthetic procedures for preparation of biocompatible phosphorus containing star-shaped glycopolymer and drug conjugate.

Synthesis and characterization of novel energetic plasticizers based on poly glycidyl nitrate

ABSTRACT Energetic plasticizers are used in propellants to increase the energy content and improve the glass transition temperature and mechanical properties. The compatibility between polymer and plasticizer is an important criterion for obtaining the best thermomechanical properties. In this research, novel energetic plasticizers were synthesized via end-group modification of poly glycidyl nitrate. Firstly, low molecular weight poly glycidyl nitrate (PGN) (Mn = 523 g.mol−1) and dinitropropyl poly glycidyl nitrate (DNPPGN) (Mn = 1700 g.mol−1) were synthesized by ring-opening polymerization of glycidyl nitrate with 1,4-butanediol and 2,2-dinitro-1,3-propanediol as initiators, respectively, and in the presence of boron trifluoride etherate (BF3.OEt2) as the catalyst. Tetra nitro poly glycidyl nitrate (TNPGN) was synthesized through end-group modification of DNPPGN and also azide-terminated GAP (GAPA) synthesized via modification of PGN as novel energetic plasticizers. The chemical structure of plasticizers was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (NMR). Thermal behaviors were investigated by differential scanning calorimeter (DSC). The thermal analysis of plasticizers indicated Tg of TNPGN is lower than PGN and other synthesized plasticizers. Also, decomposition temperature (thermal stability) of TNPGN (251°C) is higher than PGN (209°C). Therefore, TNPGN has potential as a novel energetic plasticizer for propellant.

An Efficient One-Pot Protocol for Direct Access to Diarylmethyl Thioglycosides with para-Quinone Methides via S-Glycosyl Isothiouronium Salts

An efficient one-pot protocol has been developed for the direct preparation of diarylmethyl thioglycosides starting from per-O-acetylated sugars via glycosyl isothiouronium salts. The one-pot reaction conditions involve rapid conversion of the per-O-acetylated sugar with thiourea in the presence of boron trifluoride etherate as catalyst to give the corresponding glycosyl isothiouronium salt, which is subsequently treated with a para-quinone methide in the presence of a base to give the a diarylmethyl thioglycoside in excellent yield.

Pyrocatechol borates: Synthesis, reaction with formaldehyde, and solvent effect on polycondensation process

Pyrocatechol (I) and dipyrocatechol (II) borates were synthesized by esterification between pyrocatechol (1,2-dihydroxybenzene) and boric acid in о-xylene with azeotropic distillation of water. The co-esterification between pyrocatechol and boric acid with added equimolar quantities of phenol or 2,6-di-tert-butylphenol was studied, and pyrocatechol phenyl (III) and pyrocatechol-(2,6-di-tert-butyl)phenyl (IV) borates were prepared. The reaction of the resultant esters with formaldehyde in the presence of boron trifluoride etherate as a catalyst was examined. The coupling of the methylene moiety in several position of molecule III was found to be dependent on the solvent used. The electrophilic substitution on the phenol substituent took place in о-xylene, while the reaction in either benzene or molten monomer proceeded to substitute the methylene moiety for the proton on the catechol moiety. The molecular weights of the compounds were measured. Some properties of the synthesized oligomers were determined and thermal and thermooxidative destruction was examined.

Synthesis, thermal stability and kinetic decomposition of triblock copolymer polypropylene glycol–poly glycidyl nitrate–polypropylene glycol (PPG–PGN–PPG)

An energetic triblock copolymer PPG–PGN–PPG (Mn = 1886 g mol−1) was synthesized for the first time by cationic ring-opening polymerization of propylene oxide with low molecular weight poly glycidyl nitrate (PGN) (Mn = 1061 g mol−1) as a macroinitiator, in the presence of boron trifluoride etherate (BF3·OEt2) as the catalyst. The product obtained in high yield was characterized by FTIR, gel permeation chromatography and 1H and 13C NMR spectroscopy. The thermal properties of the triblock copolymer were characterized by differential scanning calorimeter (DSC). The result approved that the glass transition temperature of the triblock copolymer (Tg = − 58 °C) is lower than PGN (Tg = − 35 °C); also, it was more stable than that of PGN. The effect of heating rates (10, 20, 30 and 40 °C min−1) on the decomposition of the copolymer was evaluated. The decomposition temperature of this compound increased as the heating rate increased. The kinetic parameters such as activation energy and frequency factor for the thermal decomposition of the triblock copolymer were obtained from the DSC and DTG data by non-isothermal methods proposed by the ASTM E696, Flynn–Wall–Ozawa (FWO) and Kissinger methods. The values by the FWO method are in good agreement with ASTM and Kissinger methods.

SYNTHESIS OF GLYCIDYL AND THIOGLYCIDYL ETHERS OF DIACETYLENE SERIES AND THEIR USE AS A MODIFIER OF PHENOL-FORMALDEHYDE OLIGOMERS

It has been shown that the chlorine-containing unconjugated enyne alcohols react with epichlorohydrin in the presence of boron trifluoride etherate with formation of chlorohydrines, which further without their isolation, under the action of potassium hydrochloride are dehydrochlorinated with formation of the corresponding glycidyl ethers. Under the action of an alcoholic solution of potassium hydroxide at temperature of 75-80 °С on synthesized chlorine-containing ethers the dehydrochlorination reaction on double С=С bond proceeds and glycidyl ethers of 1,4-diine series are formed. It has been revealed that the synthesized glycidyl ethers are the very reactive compounds. In patricular, it has been shown that the ethers of 1,4-diine series with the participation of oxirane ring undergo the reaction with thiurea medium of methanol at 30-35 °С, forming the corresponding tyrants. The data of IR- and NMR-spectra of the prepared compounds have been presented and their modifying properties in relation to phenol-formaldehyde oligomers in acidic and alkaline media have been revealed. The prepared modified oligomers are the products of liquid-viscous consistency, soluble in acetone, tetrahydrofuran, dimethyl formamide and dioxane. It has been proved by the carried out analyses that the prepared PhFOs, modified by glycidyl and thiglycidyl ethers of diacetylene series are not mechanical mixtures of phenol, formaldehyde and modifier. On the basis of obtained results the formation mechanism of modified resol and novolac PhFO has been also revealed. It has been established that the physical-chemical and physical-mechanical parameters of the prepared phenol-formaldehyde oligomers modified by modifiers proposed by us, in comparison with unmodified ones, are improved. From the proposed diglycidyl and thiodiglycidyl ethers for the modification of PhFO the best results on all parameters are achieved at modification with thioglycidyl ether of diacetylene series.

Stereoselective synthesis of novel thioglycosyl heterocycles

In this work, the synthesis of novel 1,2,4-triazole thioglycoside heterocycles 4, 5, and 8 were achieved by the reaction of 1,2,3,4,6-penta-O-acetyl-β-d-glucopyranose (2) and galactopyranose (3) with 4-((4-arylidene)amino)-5-methyl-1,2,4-triazole-3-thiol derivatives 1 and 6 in the presence of boron trifluoride etherate (BF3·Et2O) as a promoter under nitrogen in CH2Cl2. Exclusive β-stereoselectivity of the formed glycosidic bond was confirmed by X-ray analysis of 4 as well as its spectral data. Different stereoselectivities were observed when the acceptor 9, having an ortho phenolic OH group, was coupled with the donors 2 or 3, under the same reaction conditions. Similarly, treatment of a mixture of 1-O-acetyl-2,3,5-tri-O-benzoyl-β-d-ribofuranose (16) and the thiol acceptors 1 and 15 afforded the β-thioribofuranosides 17 and 18, respectively. The β-stereoselectivity of the reaction was confirmed by 1H, 13C, 1H1H 2D, and 1H13C 2D NMR spectral analysis.

Pyreniporphyrins: Porphyrin Analogues That Incorporate a Polycyclic Aromatic Hydrocarbon Subunit within the Macrocyclic Framework.

The first examples of porphyrin analogues incorporating pyrene units are reported. Acid-catalyzed condensation of a pyrene dialdehyde with a tripyrrane, followed by oxidation with DDQ, afforded a polycyclic aromatic hydrocarbon (PAH)-porphyrin hybrid in 38% yield. Pyreniporphyrin proved to be devoid of global aromatic character, but upon protonation aromatic mono- and dicationic species were generated. In the proton NMR spectrum for the dication, the internal CH was shifted upfield to approximately +3 ppm. NICS calculations and ACID plots confirmed the diatropic nature of these structures. Pyreniporphyrin reacted with palladium(II) acetate to give excellent yields of a palladium(II) complex that showed weakly diatropic properties. Treatment of the pyrene dialdehyde with phenylmagnesium bromide generated a dicarbinol that reacted with excess pyrrole in the presence of boron trifluoride etherate to give a tripyrrane analogue. Lewis acid catalyzed ring closure with a thiophene dialcohol in 2% ethanol-dichloromethane afforded a tetraphenylthiapyreniporphyrin in 31% yield. This porphyrinoid was nonaromatic in the free-base form but showed significant diatropicity upon protonation. These results demonstrate that PAH-porphyrin hybrids are easily accessible, and this strategy may allow the incorporation of even larger aromatic subunits.

Synthesis of Trialkylhydroxylamines by Stepwise Reduction of O-Acyl N,N-Disubstituted Hydroxylamines: Substituent Effects on the Reduction of O-(1-Acyloxyalkyl)hydroxylamines and on the Conformational Dynamics of N-Alkoxypiperidines.

The influence of the electron-withdrawing azide group on the reduction of O-(1-acyloxy-ω-azido)hydroxylamines by triethylsilane in the presence of boron trifluoride etherate is studied and found to increase with increasing proximity to the reaction site, suggesting that the reaction proceeds by way of aminoxocarbenium ion intermediates. The ability to carry azides through the reaction sequence affords O-(ω-azidoalkyl-N,N-dialkylhydroxylamines thereby making such functionality available for use in click chemistry. A series of 4-substituted N-alkoxypiperidines were prepared and studied by variable temperature NMR spectroscopy leading to the conclusion that the rate-determining step in the stereomutation of such piperidines is the piperidine ring flip and not nitrogen inversion or rotation about the N-O bond. The process of N-O bond rotation only becomes rate determining when in the presence of pervasive steric hindrance as is the case with the N-alkoxy-2,2,6,6-tetramethylpiperidines.

Construction of Spiro[indeno[2,1‐e]pyrrolo[3,4‐b]pyridine‐10,3′‐indoline] and Indeno[1,2‐b]pyrrolo[3,4‐e]pyridine via Three‐Component Reaction

AbstractThe three‐component reaction of β‐enamino imides, isatins and indan‐1,3‐dione in refluxing ethanol in the presence of triethylamine afforded functionalized spiro[indeno[2,1‐e]pyrrolo[3,4‐b]pyridine‐10,3′‐indolines] in good yields. The similar three‐component reaction of β‐enamino imides, aromatic aldehydes and indan‐1,3‐dione in methylene dichloride in the presence of boron trifluoride etherate resulted in the corresponding indeno[1,2‐b]pyrrolo[3,4‐e]pyridine derivatives.

Boron Trifluoride‐Catalyzed Synthesis of 3‐Alkylidene‐3H‐indole N‐Oxides via Tandem Reaction of Propargylic Alcohols and Nitrosobenzenes

AbstractAn atom‐economical synthesis of 3‐alkylidene‐3H‐indole N‐oxides has been developed via a tandem reaction of propargylic alcohols and nitrosobenzenes in the presence of boron trifluoride etherate (BF3⋅Et2O) as catalyst. This method offers great potential for the synthesis of biologically important 3‐alkylidene‐3H‐indole N‐oxides and related derivatives.magnified image

Microwave-assisted synthesis of poly(glycidyl azide-co-tetrahydrofuran)

The poly(glycidylazide-co-terahydrofuran) [poly(GA-THF)] or GA-THF copolymers are recognized and established as high-energy binders in explosive systems. In present study, we have developed a greener approach for the syntheses of poly(glycidylazide-co-tetrahydrofuran) copolymers using microwave (MW) irradiation technique. Polymerization of epichlorohydrin and tetrahydrofuran was carried out in the presence of borontrifluoride etherate and ethylene glycol to afford polyepichlorohydrin-tetrahydrofuran (PECH-THF) copolymer followed by its reaction with sodium azide in DMF under microwave irradiation to give poly(GA-THF). The poly(GA-THF) copolymer and their precursors were characterized by various spectral techniques such as MS, 1H-NMR, 13C-NMR, UV–visible, and FTIR. The thermal analysis was done by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Molecular weights of these copolymers were determined using GPC techniques. Morphology of these copolymers was visualized using SEM. Our experimental study shows that the microwave irradiation was effective for the second step (azidation reaction) than conventional heating for the synthesis of GA-THF copolymers. Also, the benign syntheses were tackled and explored with range of solvents. Thus, the current methodology, might advent the researchers dealing with these high-energy binder materials in future.

Stereoselective synthesis of tetrahydropyran new derivatives underlain by α-allyl ketones

Decarboxylation of α-allyl-substituted acetoacetic esters afforded α-allyl ketones that were reduced with L-selectride [LiBH(s-Bu)3] in alcohols RCH(OH)CH2CH2CH=C(Me)CH2R'. The latter reacted with methyl 4-hydroxy-3-formylbenzoate and methyl orthoformate in the presence of p-toluenesulfonic acid to provide trans-tetrahydropyrano[3,2-с][1]benzopyran. In reaction of the E-isomer of alcohol Me2CHCH(OH) CH2CH2CH=C(Me)CH2CH2Ph with CF3SO3H a stereoselective cyclization occurred with the formation of 2,6-disubstituted tetrahydropyran; Prins reaction with 4-bromobenzaldehyde and salicylaldehyde in the presence of boron trifluoride etherate also proceeded stereoselectively giving a substituted tetrahydropyrano-[3,2-c][1]-benzopyran.

Expeditious and Convenient Synthesis of Polycyclic Difluoroboron Complexes of 2‐Oxoindoline‐3‐carboxamides by Tandem Reaction

AbstractN‐Aryl‐2‐cyanodiazoacetamides produce polycyclic difluoroboron 2‐oxoindoline‐3‐carboxamide complexes (up to pentacyclic conjugative and fused systems) directly and expeditiously in the presence of boron trifluoride etherate. The boron trifluoride serves as both a catalyst and reactant in the tandem reaction. The tandem reaction includes the carbene aromatic CH insertion, hydrolysis of the cyano group into an amide group, and boronation of the two amide carbonyl groups. The synthetic method features the advantages of wide substrate scope and excellent chemoselectivity.magnified image

ChemInform Abstract: Regioselective C2‐ and C8‐Acylation of 5,11‐Dihydroindolo[3,2‐b]carbazoles and the Synthesis of Their 2,8‐Bis(quinoxalinyl) Derivatives.

An efficient approach for the double acetylation of 5,11-dihexyl-6,12-di(hetero)aryl-substituted 5,11-dihydroindolo[3,2-b]carbazoles with acetic anhydride in the presence of boron trifluoride etherate has been developed, thus affording the corresponding 2,8-diacetyl derivatives in good yields. A similar acylation has been shown to occur by the reaction of anhydrides of other carboxylic acids. Oxidation of the obtained 2,8-diacetyl derivatives with selenium dioxide takes place on heating or under microwave irradiation, thus resulting in the formation of the corresponding 2,8-diglyoxals. The latter proved to react with aromatic o-diamines to afford new indolo[3,2-b]carbazoles bearing quinoxalinyl fragments at C-2 and C-8. Major optical properties of quinoxaline-containing indolo[3,2-b]carbazoles have been measured.