Boron trifluoride, diethyl etherate catalyst

Since 1900 other methods have been devised for producing polymethylene , including the use of boron trifluoride-diethyl ether catalysts at 0°C. Some of these methods give unbranched linear polymers, often of very high molecular weight, which are useful for comparing commercial polyethylenes which have molecules that are branched to varying extents. 

The pharmaceutical interest in the tricyclic structure of dibenz[6,/]oxepins with various side chains in position 10(11) stimulated a search for a convenient method for the introduction of functional groups into this position. It has been shown that nucleophilic attack at the carbonyl group in the 10-position of the dibenzoxepin structure renders the system susceptible to water elimination. Formally, the hydroxy group in the enol form is replaced by nucleophiles such as amines or thiols. The Lewis acids boron trifluoride-diethyl ether complex and titanium(IV) chloride have been used as catalysts. 

A -( 1-Chloro- or bromoalkyl)amides are generally moisture-sensitive, unstable compounds, which are often directly used without further purification. Standard Lewis acids such as boron trifluoride-diethyl ether, aluminum(lll) chloride, zinc(II) chloride, tin(IV) chloride and titani-um(IV) chloride are used to generate the /V-acyliminium ion, although sometimes a catalyst is not necessary. 

The interaction of alkenes with xenon difluoride has been successful in the presence of a catalyst. Dec-l-ene treated with xenon difluoride in the presence of a boron trifluoride-diethyl ether complex in dichloromethane formed 1,1-difluorodecane (26%) and a mixture of 1-fluoro-decene isomers (48%). Under the same conditions 2-fluoro-2,2-dinitroethyl vinyl ether has been converted to T,2 -difluoroethyl-2-fluoro-2,2-dinitrocthyl ether.27... 

There are some reactions in which boron trifluoride and boron trifluoride-diethyl ether complex are used as fluorinating agents, but they are not so frequently used and widespread. The best-known reaction is the decomposition of fluoroformates. In this type of reaction boron trifluoride or pyridine are essentially required as catalysts for the decomposition process. The formation of fluoroformates is established4 5 and the decomposition proceeds cither by heating in pyridine at higher temperature6 or by addition of boron trifluoride-diethyl ether complex at 0-50°C.7... 

Aromatic nitro compounds can be converted to the corresponding 4-fluoroanilines if the 4-position carries a hydrogen atom. Thus, nitrobenzene can be converted to 4-fluoroaniline with 100% conversion and 95% selectivity by heating with hydrogen under pressure [platinum(IV) oxide catalyst] in the presence of boron trifluoride-diethyl ether complex at 42°C for 12.5 hours. 3-Chloro-l-nitrobenzene can be similarly hydrogenated-fluorinated to 3-chloro-4-fluoroaniline.25,26... 

The reaction of norbornene (5) with xenon difluoride in dichloromethane at various temperatures and in the presence of various catalysts results in the formation of seven products.45 Table 6 shows the significant effect of boron trifluoride-diethyl ether complex as catalyst in the product formation. 

Xenon difluoride reacts with alcohols to form unstable alkoxyxenon fluoride intermediates. Alkoxyxenon fluorides react as positive oxygen electrophiles when boron trifluoride-diethyl ether complex is used as a catalyst. However, these alkoxyxenon fluorides react as apparent fluorine electrophiles with proton catalysts (hydrogen fluoride generated in situ).49... 

Boron trifluoride-diethyl ether complex is used as catalyst in addition reactions of hydrogen fluoride to double bonds. If the alkene is halogenated on the C = C bond, fluorine adds to the carbon that bears the halogen.51... 

Cyclic oligomers with x - 2-9 are found to be present in poly(1,3-dioxolane) samples prepared by monomer-polymer-equilibrations using boron trifluoride diethyl etherate as catalyst. The molecular cyclization equilibrium constants 7fx are measured and the values are in agreement with those calculated by the Jacobson-Stockmayer theory, using an RIS model to describe the statistical conformations of the corresponding chains and assuming that the chains obey Gaussian statistics. 

Aluminum trichloride is the most commonly used catalyst, although aluminum tribromide is more efficient.1 For the rearrangement of l-broino-2-chloro-1,L2-lrifluoroethane (3) to 2-bromo-2-chloro-l,l,l-trifhioroethane (4). none of the following Lewis acids are effective iron(III) chloride. iron(III) bromide, antimony(III) chloride, antimony(V) chloride. tin(IV) chloride, titanium(IV) chloride, zinc(II) chloride, and boron trifluoride-diethyl ether complex.1" ... 

The catalysts used successfully in the liquid phase in the order of their efficiency are anti-niony(V) chloride, aluminum tribromide, aluminum trichloride, and iron(Ill) chloride. Zinc(ll) chloride, tin(ll) chloride, boron trifluoride diethyl ether complex, and aluminum trifluoridc do not catalyze the dismutation. 

For instance, in cases where the mechanism of the propagation of the polymer chain is by means of cationic polymerization, the rate increases with the polarity of the solvent. Thus, when the boron trifluoride-diethyl ether complex is used as the catalyst for styrene polymerization, then at 0°C the rate equation for a series of solvents takes the simple form of dependence on the solvent polarity (Heublein 1985) ... 

When the reactions of benzenetellurinyl acetate or trifluoroacetate to olefins were carried out with nitriles as solvents and boron trifluoride diethyl etherate as catalyst, 2-acylamino-1-alkyl phenyl telluroxides were obtained. Telluroxide elimination produces 4,5-dihydrooxazoles2. 

Suitable catalysts are pyridine, - dimethylformamide, tertiary amines.or Lewis acids such as boron trifluoride-diethyl ether complex, e.g. fomiation of The decarboxylation reaction is carried out under anhydrous conditions and in an inert gas atmosphere. 

The acid-catalyzed reaction of enol silyl ethers of cyclic ketones with optically active methyl 4-methylphenylsulfinate has been reported as a very efficient method for the synthesis of chiral a-sulfinyl cycloalkanones 212. Boron trifluoride-diethyl ether, titanium tetrachloride and tin(IV) chloride may all be used as catalysts, however, the reproducibility of this procedure has recently been questioned71. 

Substituted quinazolines 49 are conveniently prepared by the action of formamide on 2-aminophenyl alkyl, aryl, and arylalkyl ketones 48 in the presence of boron trifluoride diethyl ether complex as catalyst.This variation gives good yields and cleaner products than the method- in which formic acid is used as catalyst. 

The main drawback in the catalytic hydrogenolysis of Z-protected peptide derivatives is caused by the presence of sulfur-containing amino acid residues (Cys, Pen, or Met) due to catalyst poisoning. Attempts to overcome these restrictions by addition of either tertiary basesf or boron trifluoride-diethyl ether complext to the hydrogenation mixture were of limited usefulness. More efficient appears to be the use of liquid ammonia (at —33°C) as the solvent to prevent poisoning of the Pd/C catalyst.f °l... 

The five membered cydic 1,3-dioxolane (CHjOCHjCHjO) can be polymerised by a variety of catalysts including sulphuric acid (P7), perchloric acid (98), phosphorus pentachloride (PP) and alkyl aluminium compounds with water as a co-catalyst (100). The effect of the catalyst boron trifluoride diethyl etherate on the polymerisation of 1,3-dioxolane has also been studied and it has been found that equilibrium between monomeric 1,3-dioxolane and poly(l, 3-dioxolane) is set up in both the undiluted polymer and in solution (101-104). Controverf has arisen as to whether the equilibrium is between cyclic monomer and cyclic polymer (98) or between cyclic monomer and chain polymer (104). 

When 2-crotyloxypyridine (63) was heated under similar conditions, however, the results were catalyst dependent (Scheme 5). With boron trifluoride-diethyl ether as catalyst, an 82 18 mixture of the pyridones 64 and 65 was obtained, whereas the H2PtCl6-catalyzed reaction gave a [3,3]-rearrangement product, the pyridone 66 (68JOC4560). Interestingly, when Pt(PPhj)4 was used as catalyst, 63 and 2-(l-methylallyloxy)pyridine (67) both gave the same 14 86 mixture of the pyridones 64 and 66, suggest-... 

Similar reactions of norbornadiene with substituted buta-1,3-dienes in the presence of cobalt catalysts lead to the corresponding 1,4-adducts in 92-96% yield.In the presence of chiral phosphane ligands, this reaction has been brought about with up to 79% enantiomeric excess. The head-to-head dimer of norbornadiene, 1,2,4 5,6,8-dimethano-5-indacene (3, Binor-S ) was formed in quantitative yield on dimerizing norbornadiene with catalysts such as co-balt(II) bromide/triphenylphosphane, cobalt(ll) iodide/triphenylphosphane, or (triphenylphos-phanejrhodium chloride, in the presence of boron trifluoride-diethyl ether complex. ... 

Cyclopropanecarbaldehydes, 1,1-dialkoxy-l-cyclopropylalkanes and cyclopropyl ketones reacted readily with ethanedithiol " " " and propanedithioP to give the corresponding 1,3-dithiolanes and 1,3-dithianes, respectively, in excellent yield. Boron trifluoride diethyl ether complex, in the presence or absence of acetic acid, has generally been used as the catalyst, but hydrogen chloride has also been utilized.An example of this reaction is the formation of the dithioacetal of cyclopropanecarbaldehyde 3. ... 

Various substituted benzimidazoles have been synthesized in very good yields in solvent-free conditions from 1,2-diaminobenzene and aldehydes in the presence of titanium(IV) chloride as a catalyst. The method is applicable to most aromatic, unsaturated and aliphatic aldehydes and to substituted 1,2-diaminobenzenes without significant differences [14]. Several other catalysts, namely iodine [15], hydrogen peroxide [16], zirconyl(IV) chloride [17], boron trifluoride diethyl etherate [18], ytterbium perfluorooctane sulfonates [19,20], zeolite [11,21], and L-proline [22], have been effectively used for the synthesis of benzimidazole derivatives. 

The use of boron trifluoride diethyl ether complex as a catalyst allowed the synthesis even of very sensitive systems, as exemplified by the cyclopropenone (336) leading to 24-58% yield of the corresponding 4,7-dithiospiro[2.4]heptanes (337) (Equation (70)) <87S393>. 

Even unsymmetrically substituted 1,3-diketones (338) are transformed into 1,3-dithiolanes (339) and (340) with boron trifluoride diethyl ether complex as a catalyst, as long as the reaction temperature does not exceed 15°C (Scheme 61) <88T2283>. 2-Oxo-aldehydes (341) react with ethane-... 

Michael adducts 58 and 2-ethoxy-3,4-bis(methoxycarbonyl-3//-benzo-djazepine (59). The latter product was obtained in 20% yield. 2-Ethoxy-1-methyl-1//-indole (57, R = CH3) yielded exclusively the corresponding 1//-benzo[ ]azepine (60), in a much higher yield (72%). The (2 + 2)-cycloadduct (61) was proposed to be the unstable intermediate in both reactions. 1,3-Dimethyl-1//-indole (62a) was reported to react with dimethyl acetylenedicarboxylate only in the presence of boron trifluoride diethyl etherate as a catalyst.65 In the reaction mixture, two isomeric Michael adducts and a thermally unstable product were... 

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