Boron trifluoride complex with

Takahashi and coworkers described the one-pot synthesis of core 2 branched oligosaccharides [236], It was found that boron trifluoride complexed with a tri-methylsilyl ether would enhance the nucleophilidty of the silyl ether. As a result, glycosylations of the 6-O-TMS modified acceptor with a glycosyl fluoride provided... 

Small Quantities. Wear nitrile rubber gloves, laboratory coat, and eye protection. In the fume hood, pour the boron trifluoride complex into a large evaporating dish. Cover the boron trifluoride complex with excess solid sodium carbonate or calcium carbonate. When the reaction has subsided, very slowly add the mixture to a pail of cold water. Allow to stand for 24 hours. Test the pH of the solution and neutralize if necessary. Wash the solution into the drain.2-5... 

With respect to this reaction, weak bonds are formed between the oxygen of the oxirane ring and one hydrogen atom of the amine. This explanation is also supported by Ito and Okahashi [91]. In addition, they have suggested a termination in which boron trifluoride complexes with tertiary amine are produced ... 

Acylation may also be effected with the acetic acid - boron trifluoride complexes BF3.CH3COOH and BF3.2CH3COOH. 

Cationic polymerization of coal-tar fractions has been commercially achieved through the use of strong protic acids, as well as various Lewis acids. Sulfuric acid was the first polymerization catalyst (11). More recent technology has focused on the Friedel-Crafts polymerization of coal fractions to yield resins with higher softening points and better color. Typical Lewis acid catalysts used in these processes are aluminum chloride, boron trifluoride, and various boron trifluoride complexes (12). Cmde feedstocks typically contain 25—75% reactive components and may be refined prior to polymerization (eg, acid or alkali treatment) to remove sulfur and other undesired components. Table 1 illustrates the typical components found in coal-tar fractions and their corresponding properties. 

Primary nitroparaffins react with two moles of formaldehyde and two moles of amines to yield 2-nitro-l,3-propanediamines. With excess formaldehyde, Mannich bases from primary nitroparaffins and primary amines can react further to give nitro-substituted cycHc derivatives, such as tetrahydro-l,3-oxa2iaes or hexahydropyrimidines (38,39). Pyrolysis of salts of Mannich bases, particularly of the boron trifluoride complex (40), yields nitro olefins by loss of the amine moiety. Closely related to the Mannich reaction is the formation of sodium 2-nitrobutane-1-sulfonate [76794-27-9] by warming 1-nitropropane with formaldehyde and sodium sulfite (41). 

Other THF polymerization processes that have been disclosed in papers and patents, but which do not appear to be in commercial use in the 1990s, include catalysis by boron trifluoride complexes in combination with other cocatalysts (241—245), modified montmorrillonite clay (246—248) or modified metal oxide composites (249), rare-earth catalysts (250), triflate salts (164), and sulfuric acid or Aiming sulfuric acid with cocatalysts (237,251—255). 

Table 8-11. Enthalpy Change for Boron Trifluoride Complex Formation with Donors al 25°C...

Aniline (27.9 g, 0.3 mol) was added dropwise over a period of 30 min to a stirred solution of BF3 OEt2 (42.6 g, 10.3 mol) in anhyd benzene (100 mL) cooled to 10°C. After additional stirring at rt for 30 min, the crystalline precipitate was filtered with suction and washed with anhyd benzene (4 x 25 mL) portions to give the aniline-boron trifluoride complex yield 47.7 g (97%). 

Boron trifluoride complexes are also often applied. BF3 when used with acyl fluorides showed in some cases distinct differences compared to other catalyst-reagent combinations. For example, acylation of 2-methylnaphthalene with isoBuCOF and BF3 gives high yield (83%) of the 6-substituted isomer in contrast to AICI3 (30%).40 A similar example is shown here ... 

Effect of reaction mixture composition on the acidity of supported boron trifluoride complex as measured by spectrosopic titration with pyridine. 

Typical reaction profile for the reaction of phenol with cyclohexene catalysed by supported boron trifluoride complex... 

In practice the epoxide-amine cure is often accelerated by the addition of catalysts such as boron trifluoride complexes, and the boron trifluoride-ethylamine adduct (BFE) is widely used for this purpose. In addition to catalysing the epoxide-amine reactions, BFE can initiate homopolymerisation of epoxide. The accelerating effect of BFE is illustrated by DSC scans for the TGDDM/DDS/BFE system in Figure 12. The multiple-peaked exotherm associated with the BFE-catalysed TGDDM/DDS cure indicates that the kinetics of this system are more complex than those for the cure with amine alone. For this system the overall heat of reaction was found to decrease with increasing BFE concentration 89). For DDS alone Q0 was about 110 kJ per mole epoxide while the value for BFE alone was 75 kJ/mole, and the DDS/BFE values were between these limits. It appears that the proportion of epoxide homo-polymerisation relative to amine or hydroxyl addition increases with increasing BFE concentration. 

Dehydrofluorination of methyl 2f/-hexafluoroisobutanoate (11) using the triethylamine-boron trifluoride complex (81 % yield)92 or by heating with sodium fluoride93 gives methyl per-fluoro(methacrylate) (12). 

Hcxafluoro-Ar,/V-dimethylisobutanamide (15) and A,A -diethyl-2//-hexafluoroisobutan-amide (17) on reaction with the triethylamine-boron trifluoride complex give /V.A -dimethyl-perfluoro(methacrylamide) (16) and TV.N-diethylpertluoro ethacrylamide) (18), respectively.92... 

Bisphenylhydrazone complexes 50 and 52 of the corresponding polyfluorinated a-diketones with triethylamine or the triethylamine boron trifluoride complex give the pyrazoles 51143 and 53.119... 

The most popular catalysts for epoxy resins are tertiary amines, tertiary amine salts, boron trifluoride complexes, imidazoles, and dicyandiamide. Many of these catalysts provide very long pot lives (months) at room temperatures and require elevated temperatures for reaction with the epoxy groups. These catalysts are often referred to as latent hardeners. 

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