Trifluoride Complexes Research Articles

The microwave spectrum and structure of the neon-phosphorus trifluoride complex

Symmetric top spectra were observed for the 20Ne·PF 3 and 22Ne·PF 3 van der Waals dimers using a Fourier-transform microwave spectrometer. The center-of-mass distance between Ne and PF 3 is 3.373(3) Å. The experimental data, in conjunction with the van der Waals radii of the atoms and with ab initio calculations, are consistent with the neon atom on the symmetry axis over the F 3 face of the PF 3. Normal mode analysis of the van der Waals vibrations based on the centrifugal distortion constants yields force constants f R = 0.00647 mdyn Å −1 and f Θ = 0.00464 mdyn Å for the 20Ne·PF 3 isotopic species.

Synthesis of 3-Alkoxyalkanoic Esters from Acetals. A Novel Application of Reformatsky Reagents in Asymmetric Synthesis

3-Alkoxyalkanoic esters are directly obtained in high yield from the reaction of acetals with Reformatsky reagents in the presence of titanium(IV) chloride or diethyl ether-boron trifluoride complex in dichloromethane. The reaction of ethyl 4-bromo-2-butenoate is regioselective, affording the product formed by attack on the 4-position. With chiral acetals as substrates, up to 84% enantiomerically enriched 3-hydroxyalkanoic esters can be prepared.

Intramolecular electron transfer in the novel photoreaction of some β,γ-unsaturated oxime–boron trifluoride complexes. A new synthetic path to dihydroisoxazoles

β, γ-Unsaturated oximes are photochemically reactive in benzene solution when irradiated in the presence of boron trifluoride–diethyl ether; typically 2,2-dimethyl-4,4-diphenylbut-3-enal oxime affords a low yield of 2,2-diphenyl-3,3-dimethylcyclopropanecarboxaldehyde by the aza-di-π-methane rearrangement, and a principal product (48%) identified by X-ray diffraction analysis as 4, 4-dimethyl-5-(diphenylhydroxymethyl)-4,5-dihydroisoxazole.

A Lewis Acid Catalyzed Rearrangement of Allenol Ethers

Allenol ethers (1,2-propadien-1-ol and 1,2-butadien-1-ol derivatives) have been found to undergo, under the catalytic influence of diethyl ether-boron trifluoride complex, a 1,3-intermolecular rearrangement, leading to variously 2-substituted α,β-unsaturated carbonyl derivatives.

ChemInform Abstract: Synthesis, Stereochemistry, and Isomerization of 4‐Aryl‐5‐aroyl‐2‐methyl‐2‐imidazolines.

AbstractTreatment of the trans‐ (I) or cis‐arylaroylaziridine boron trifluoride complexes (V) with methyl thiocyanate (II) gives regio‐ and stereoselectively the cis‐ (III) or trans‐imidazolines (VI) which are converted to the free bases (IV) or (VII) upon treatment with triethylamine.

ChemInform Abstract: Ring Contraction During the Reactions of Cyclic Olefins with Iodine(III)‐Containing Reagents.

AbstractCyclohexene (I) or the dihydropyran (III) react with phenyliodonium sulfate or the iodosobenzene‐boron trifluoride complex under ring contraction to give the aldehydes (II) or (IV).

ChemInform Abstract: Synthesis of Azetidin‐3‐ones by Heterocyclization of α‐Cyclohexylamino‐α′,β′‐epoxy Ketones.

AbstractThermal treatment of the boron trifluoride complexes (I) of amino epoxy ketones gives hydroxymethylazetidinones (II) which are converted to the derivatives (III), (V), and (VI).

Synthesis of Methyl 5-Aryl-3-oxo-4-pentenoates and Novel Substituted Cyclopentenones

The cinnamoyl- (1a-j) and (5-phenyl-2,4-pentadienoyl)- (1k) ketene dithioacetals are shown to undergo methanolysis in the presence of ether-boron trifluoride complex and mercury(II) chloride to the corresponding methyl 5-aryl-3-oxo-4-pentenoates 2a-j and 3-oxo-7-phenyl- 4,6-heptadienoate (2k), respectively, in good yields. However, the corresponding (2-methylcinnamoyl)ketene dithioacetals 3a-f, under identical reaction conditions, undergo Nazarov cyclization to give the corresponding substituted cyclopentenones 4a-f.

ChemInform Abstract: Synthesis of Pyrrolidine Derivatives by Improved Aminoselenation via Addition of Boron Trifluoride Complex of Dihomoallylcuprate to Aldimines Containing α‐Hydrogen.

AbstractThe unsaturated amines (III) derived from the imines (I) are cyclized and selenenylated to give the phenylselenenylmethylpyrrolidines (V) which are reduced, forming the methylpyrrolidines (VI).

ChemInform Abstract: A Novel Route to Stilbenes via Cationic Cycloaromatization.

A novel route for substituted stilbenes 3a-j is developed by cationic cycloaromatization of the corresponding (α-allyl-α-hydroxycinnamyl)-ketene dithioacetal derivatives 2a-j in the presence of ether-boron trifluoride complex. The hydroxydithioacetals 2a-j were obtained by 1,2-addition of allyl or crotyl magnesium bromide with the respective styryl β,β-bis(methylthio)vinyl ketones 1a-j.

A Novel Route to StilbenesviaCationic Cycloaromatization

A novel route for substituted stilbenes 3a-j is developed by cationic cycloaromatization of the corresponding (α-allyl-α-hydroxycinnamyl)-ketene dithioacetal derivatives 2a-j in the presence of ether-boron trifluoride complex. The hydroxydithioacetals 2a-j were obtained by 1,2-addition of allyl or crotyl magnesium bromide with the respective styryl β,β-bis(methylthio)vinyl ketones 1a-j.

Aliphatic CH, N-insertion versus aromatic N-substitution in the reaction of arylnitrenium-boron trifluoride complexes with methylated benzenes

The boron trifluoride promoted decomposition of a number of substituted phenyl azides in toluene, para -xylene, meta -xylene or mesitylene at 60°C, leads preferentially to N -benzylamines or diarylamines depending on both ring substituent effect and nucleophilic character of the solvent.

Polarized Ketene Dithioacetals; 55:1Synthesis of Novel 5-Aryl-2-methylthio-4H-pyran-4-ones from Cinnamoylketene Dithioacetals

A novel method for the synthesis of 5-aryl-2-methylthio-4H-pyran-4-ones 4a-h has been developed from the corresponding cinnamoylketene dithioacetals 1a-h in three successive steps. In the first step, 1a-h were oxidized with alkaline hydrogen peroxide to give the corresponding (β-aryl-,α,β-epoxypropanoyl)ketene dithioacetals 2a-h in 78-89% overall yields. In the second step the epoxyketones 2a-h were subjected to rearrangement in the presence of ether-boron trifluoride complex to give the corresponding (α-formyl-α-phenylacetyl)ketene dithioacetals 3a-h, which were then cyclized in the third step by refluxing in acetic acid/ethanol to afford the title compounds in good yields.

ChemInform Abstract: The Molecular Structures of Complexes of Pyridine with Boron Trifluoride, Boron Trichloride and Boron Tribromide as Studied by Gas Phase Electron Diffraction.

Abstract The molecular structures of pyridine complexes with boron trifluoride, boron trichloride and boron tribromide have been determined from gas electron-diffraction data. The molecular parameters of the boron trifluoride complex are r g (NB) = 1.669(7) A, r g (BF) = 1.366(2) A, ∠FBF = 113.3(4)°, r g (CN) = 1.345(6) A and r g (CC) = 1.382(4) A. The corresponding values for the boron trichloride complex are 1.706(12) A, 1.830(3) A, 112.5(3)°, 1.360(10) A and 1.390(6) A, and those of boron tribromide complex are 1.694(17) A, 1.986(3) A, 111.9(3)°, 1.362(12) A and 1.392(8) A. On complex formation the structure change of the acceptor molecules is much larger than that of the donor molecule and increases with the increase of atomic number of the halogen atoms.

The molecular structures of complexes of pyridine with boron trifluoride, boron trichloride and boron tribromide as studied by gas phase electron diffraction

The molecular structures of pyridine complexes with boron trifluoride, boron trichloride and boron tribromide have been determined from gas electron-diffraction data. The molecular parameters of the boron trifluoride complex are r g(NB) = 1.669(7) Å, r g(BF) = 1.366(2) Å, ∠FBF = 113.3(4)°, r g(CN) = 1.345(6) Å and r g(CC) = 1.382(4) Å. The corresponding values for the boron trichloride complex are 1.706(12) Å, 1.830(3) Å, 112.5(3)°, 1.360(10) Å and 1.390(6) Å, and those of boron tribromide complex are 1.694(17) Å, 1.986(3) Å, 111.9(3)°, 1.362(12) Å and 1.392(8) Å. On complex formation the structure change of the acceptor molecules is much larger than that of the donor molecule and increases with the increase of atomic number of the halogen atoms.

Epoxy resin cure III: Boron trifluoride catalysts

AbstractBoron trifluoride forms complexes with nitrogen‐and oxygen‐containing Lewis bases. These acid–base complexes are sometimes added to epoxy resins to accelerate their cure at elevated temperature (120°C–160°C). Several possible processing concerns with the use of boron trifluoride complexes have been investigated. It was shown that each complex can be readily identified by its distinct fluorine‐19 NMR spectrum. All of the boron trifluoride complexes are converted to fluoroboric acid under normal epoxy resin cure conditions. The fluoroboric acid is the true catalyst for epoxy resins. Experimental results show that fluoroboric acid does not catalyze the polymerization of an epoxy resin at room temperature. Finally, it was shown that fluoroboric acid is not hydrolyzed to hydrofluoric acid.

Thermal stability of epoxy compounds cured with boron trifluoride complexes

The thermal resistances of epoxy resins cured with complexes of boron trifluoride with benzylamine, 2-benzylaminoethanol and 2-anilinoethanol were examined. Thermal analysis data were used to compare the thermal resistances of epoxy compusitions cured with polyamines (aliphatic and aromatic), acid anhydrides and complexes of boron trifluoride with the above amines.

Addition of boron trifluoride complexes of organocopper reagentsto aldimines containing α-hydrogens

RCu · BF 3, generated in situ from Grignard reagents, CuI, and BF 3 · OEt 2, added to aldimines containing α-hydrogens to afford secondary amines in good yields. Boron trifluoride complex of dialkylcuprate gave essentially the same result with wider application.

Proton and fluorine nuclear magnetic resonance studies of molecular motion in dimethyl sulfoxide-boron trifluoride complex

Proton and fluorine second moments and spin-lattice relaxation times have been studied over a wide temperature range in solid dimethyl sulfoxide-boron trifluoride (CH 3) 2SO · BF 3 and in its deuterated analog (CD 3) 2SO · BF 3. The results indicate that the two methyl groups are dynamically inequivalent within the molecule and reorient at and above 77 K about their threefold symmetry axes ( C 3) with different frequencies and with activation energies of 6.69 and 10.45 kJ/mol. The BF 3 group is rigid at 77 K, while above 135 K it reorients about its C 3 symmetry axis with an activation energy of 15.93 kJ/mol. The low-temperature fluorine relaxation is controlled by the reorientation of the methyl groups which is faster than that of BF 3. This allows one to deduce for the fluorine-proton second moment a value indicating that the BF3 group is closer to one of the two methyl groups in the proton-containing compound.

Identification of some boron‐based curing agents in cured epoxy systems by computer‐assisted infrared spectroscopy

AbstractThe use of computer‐assisted infrared spectroscopy has allowed identification of three different boroxines and a boron trifluoride complex used as curing agents in cured epoxy resins. Boroxines were distinguished from a boron trifluoride complex by the BO stretch absorption near 1400 cm−1 in the solid state. Detection of this absorption was enhanced by spectral subtraction methods in which the reference spectrum was that of the parent resin, or a suitably cured system of similar structure. Distinction between different boroxines was achieved by analysis of the gases evolved from samples heated at 300°C in nitrogen. Identification of the alcohol fraction of the original boroxine was improved by subtraction of the spectrum of water vapor. Boron trifluoride was detected in the gases evolved at 450–500°C from BF3‐cured systems, and also in the liquid pyrolyzates. Further simplification of the 300°C gas spectra by subtraction of alcohol and carbon dioxide revealed the presence of acrolein in the gases from boroxine‐cured systems while BF3‐cured systems yielded acetaldehyde. These differences may be associated with different end groups in the cured resins.