Tris boron

Boron tri-iodide, Blj (BClj plus HI at red heat or I2 plus NaBH ), m.p. 43°C, b.p. 2iO°C. It has very similar properties to boron trichloride. 

In addition, boron, aluminum, and gallium tris(triduoromethanesulfonates) (tridates), M(OTf)2 and related perduoroalkanesulfonates were found effective for Friedel-Crafts alkylations under mild conditions (200). These Lewis acids behave as pseudo haUdes. Boron tris(tridate) shows the highest catalytic activity among these catalysts. A systematic study of these catalysts in the alkylation of aromatics such as benzene and toluene has been reported (201). 

Thermal cleavage of boron tris(trifluoromethane)sulfonate and boron tris(pen-tafluoroethane)sulfonate was studied. Careful identificadon of the products has led to the proposal of a mechanism and an account for this process [121] (equation 93). 

The present authors12,13) also studied the polymerization of 2 with boron tri-fluoride etherate as the initiator. High molecular weight polymers with intrinsic viscosities up to 1.87 dl/g were obtained in methylene chloride at —78 °C. The polymers melted at 160—180 °C, and showed some crystallinity as observed by X-ray diffraction. 

Proportional counters can also count neutrons by introducing boron into the chamber. The most common means of introducing boron is by combining it with tri-fluoride gas to form Boron Tri-Fluoride (BF3). When a neutron interacts with a boron atom, an alpha particle is emitted. The BF3 counter can be made sensitive to neutrons and not to gamma rays. 

The aldol reactions introduced thus far have been performed under basic conditions where enolate species are involved as the reactive intermediate. In contrast to the commonly accepted carbon-anion chemistry, Mukaiyama developed another practical method in which enol species can be used as the key intermediates. He is the first chemist to successfully demonstrate that acid-catalyzed aldol reactions using Lewis acid (such as TiCU) and silyl enol ether as a stable enol equivalent can work as well.17 Furthermore, he developed the boron tri-fluoromethane sulfonate (triflate)-mediated aldol reactions via the formation of formyl enol ethers. 

Isodurene, oxidation with peroxytri-fluoroacetic acid and boron tri-fluoride, 48, 90 Isodurenol, 48, 90. ... 

Boron tris(trifluoromethanesulfonate). This triflate is obtained by reaction of BC1, with triflic acid in S02C1F at -78°. Distillation at reduced pressure provides a solid, m. p. 45°, b. p. 68-73°/0.5 mm. It is extremely hygroscopic, and is soluble m CRiC, CHjNOi, CH CN. Aluminum and gallium triflate are poorly soluble in the common solvents. All three triflates can function as Friedel-Crafts catalysts, but the boron triflate is the most effective as a soluble catalyst. ... 

The first reported instance of stereoselective polymerization was probably the cationic polymerization of isobutyl vinyl ether in 1947 [Schildknecht et al., 1947]. A semicrystalline polymer was obtained when the reaction was carried out at —80 to —60°C using boron tri-fluoride etherate as the initiator with propane as the solvent. The full significance of the polymerization was not realized at the time as the crystallinity was attributed to a syndiotactic structure. X-Ray diffraction in 1956 indicated that the polymer was isotactic [Natta et al., 1956a,b], (NMR would have easily detected the isotactic structure, but NMR was not a routine tool in 1947.)... 

It easily forms double compds, such as boron trifluoride etherate. Another compd, boron tri fluoride-mono ethyl amine, BFa— C2H6NH2 is wh to pale tan flakes, melting at 88—90°. It released BFa above 110° and is used for elevated temp cure of epoxy resins Refs 1) Gmelin-Kraut Syst Number 13(1954), 168 2) CondChemDict (1961), I661L R ... 

Fig. 16. NMR profiles in CD2CI2 at 25 °C of methyl methacrylate (MMA)-Lewis acid mixtures. Relationships between the chemical shift of the C=0 signal of MMA and the mole ratio of Lewis acid to MMA Lewis acids triphenylboron ( ), tris(pentafluorophenyl)boron ( ), tri-n-butylboron (A), triphenylaluminum (O), and methylaluminum bis(2,4,6-tri-tert-butylphenolate) ( )...

Ammino-boron Tri-iodides.—Boron iodide and ammonia unite with development of heat. If dry ammonia gas is passed into a solution of boron tri-iodide in carbon tetrachloride, cooled to 0° C., a white amorphous substance of composition BI3.5NH3 is formed,3 which turns brown on exposure to light and is decomposed by water. This compound is capable of absorbing more ammonia, being transformed into a liquid of composition BI3.15NH3, which is exceedingly unstable and rapidly loses ammonia on exposure to air. These derivatives also are most probably mixtures of ammonium iodide and boron triamide. 

In this Sect, we report systematic DSC studies of (i) the constituents of boron tri-fluoride monoethylamine (BF3 NH2C2H5) catalyzed TGDDM-DDS epoxies and their mixtures (ii) the nature of the catalyzed cure reactions and (iii) the environmental sensitivity of the BF3 NH2CzH5 catalyst. DSC studies are also reported on the cure reaction characteristics and environmental sensitivity of commercial prepregs that contain BF3 amine catalysts. 

A second curious example taken from the Bteroid field concerns the reaction of 5a,6a-epoxy-B-norcholesteryl acetate with boron tri-flucride,4 which gives an unsaturatod alcohol in which the C(i -methyl has migrated in the manner depicted in Eq. (480). 

Vicinal fluoroalkyl ethers are also obtained from olefins and methyl hypo-fluorite at low temperatures [168] and from the unstable reagents generated from additions of xenon difluoride to methanol [169] or other alcohols [170] Alcohols tend to give complex product mixtures depending on the olefin structure, and best results are often achieved when reactions are run in the presence of boron tri-fluonde Additions of xenon difluoride to trifluoromcthanesulfomc fluorosulfonic, or nitric acids give fluoroxenonium reagents that are stable to about -10 °C and... 

Bannon, C.D., Craske, J.D., Hai, N.T., Harper, N.L., and O Rourke, K.L. 1982. Analysis of fatty acid methyl esters with high accuracy and reliability. II. Methylation of fats and oils with boron tri-... 

The boron halides are made either by direct reaction of the elements at high temperature or from the oxide. The most important is boron tri-... 

Since the metal-alkene association preceding the peroxymetalation reaction in mechanism (B) is a pure Lewis acid/Lewis base interaction, it would be expected that compounds having alkylperoxy groups bonded to a Lewis acid center should be active for the epoxidation of alkenes. This is indeed found for boron compounds, which are active as catalysts for the epoxidation of alkenes by alkyl hydroperoxides.246,247 Isolated boron tris(alkyl peroxides), B(OOR)3, have been shown to epoxidize alkenes stoichiometrically, presumably through alkylperoxyboration of the double bond (equation 76).248... 

Lewis superacids, such as SbF5, AsF5, PF5, TaF5, NbF5, BF3, tris(pentafluoro-phenyl) borane, boron tris(trifluoromethanesulfonate), and aprotic organic superacids developed by Vol pin and co-workers. 

Boron tris(triflate) has also been tested in the adamantylation of benzene and toluene with 1-haloadamantanes [Eq. (5.87)] and2-haloadamantanes.232B(OTf)3 is a highly active catalyst to promote the transformation in very short time under mild conditions to yield isomeric aryladamantanes and adamantane byproduct (Table 5.15). Of the isomeric 1-tolyladamantanes, 1-meto-tolyladamantane predominates, whereas the para isomer is the main product of the 2-tolyladamantanes. The ortho isomers were... 

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