Containers boron trifluoride

Cations like that present in (iv) exist in solutions of aromatic hydrocarbons in trifluoroacetic acid containing boron trifluoride, and in liquid hydrogen fluoride containing boron trifluoride. Sulphuric acid is able to protonate anthracene at a mero-position to give a similar cation. ... 

Ethylenedioxy-3(5,1 la.-dihydroxy-5a-pregnan-20-one.2 A solution of 3/ , 17a-dihydroxy-5a-pregnane-12,20-dione (8.75 g) dissolved in ethylene glycol (90 ml) containing boron trifluoride-ether complex (14 ml) is kept for 16 hr at room temperature. The solution is diluted with chloroform and washed to neutrality with water. The solution is evaporated to yield a crude ketal which is purified by crystallization from chloroform-ethyl acetate or methanol mp 255-259° (softens 252°) [a]D 74° (CHC13). 

Aldehyde 100 was cyclized to the tetracyclic enamide 101 in chloroform containing boron trifluoride at room temperature in 87% yield (75JA2503). A similar cyclization of aldehyde 102 was brought about with molecular sieves at room temperature to give 69% of the dibenzo-4-azaazulene 10 containing a fully conjugated 7i-system (82H75). 

The use of trimethylsilyldiazomethane with methanol provides a less hazardous method for preparing methyl esters under mild conditions than ethereal diazomethane solution. Trimethylsilyldiazomethane is commercially available, obviating the need to synthesize diazomethane daily. It is a stable and safe substitute for either hazardous diazomethane or corrosive reagents containing boron trifluoride. 

The mixture 5-8 (1 g) was either (1) dissolved in benzene (10 mL) containing toluene-p-sulfonic acid (5 mg), or (2) dissolved in anhydrous ether (20 mL) containing boron trifluoride-ether complex (2 drops). In each case, the mixture was stirred for 2 h at ambient temperature, then washed with aqueous sodium hydrogen carbonate and water, dried, and concentrated. The residue was chromatographed on a silica gel column with ether-light petroleum 1 1 to give initially 5 (0.25 g, 25%) [a]jj — 48.3° (c 0.77, CHClj). Continued elution gave a-L-g/ycero-isomer 8 (0.5 g, 55%) [ol]jj + 11.6° (c 0.78, CHClj). 

Methylenation of ketones. Lunn heated A -5a-androstene-3-one with DMSO containing boron trifluoride etherate in the hope of obtaining the 1,3-dione. Instead he obtained in 30% yield the 4-methylene ketone (2). He then added paraformalde-... 

Esterification. An esterifying reagent can be prepared easily by mixing boron trifluoride etherate in an alcohol. This reagent is both thorough and mild. Thus p,//-diphenyldicarboxylic acid, which is inert to diazomethane, is converted into the corresponding dimethyl ester in 40% yield when refluxed in 10% boron trifluoride etherate in methanol for three days. The very sensitive 1,4-dihydro-benzoic acid was successfully esterified by this method. The ethyl ester was obtained in 81% yield when the acid was refluxed for 20 hours in anhydrous ethanol containing boron trifluoride etherate.1... 

Aliphatic ethers are cleaved by acetic anhydride containing boron trifluoride etherate plus lithium iodide at 20° 22 the alcoholic parents of the ether are obtained as main products, together with small amounts of olefin for instance, cyclohexyl acetate and 3/S-cholestanyl acetate are formed from alkoxycyclohexanes and 3/S-alkoxycholestanes, respectively. 

Glycoside formation followed by ring closure occurred with formation of a chroman in the reaction of the 3,4,6-tri-0-benzyl-2-C-acetoxymethylgalactal shown with 4-methylphenol in dichloromethane containing boron trifluoride-etherate at 0°C to afford the a-product in 70% yield by way of the C-2-methylene-O-glucoside which could be prepared separately and converted to the same pyranobenzopyran under similar conditions (ref. 38). 

Oxidative dimerisation of a guaiacyl system, namely prestegane B, in dichloromethane containing boron trifluoride etherate was achieved in 80% yield by addition to a stirred suspension of ruthenium dioxide dihydrate in dichloromethane containing triflic acid/triflic anhydride (in the proportions 8 2 1) at 0°C followed by reaction for 3 hours (ref.73). 

Under acidic conditions a stirred mixture of resorcinol and mesityl oxide in carbon disulphide containing boron trifluoride etherate followed by refluxing for 5 hours resulted in two electrophilic substitutions and ring closure to furnish... 

Trimethoxyanthraquinone in refluxing benzene containing boron trifluoride etherate afforded after reaction during 30mins. an intermediate 4,10-chelated compound in 89% yield which with hot methanol at 50°C for lOmins. gave an 94% yield of 4-hydroxy-1,5-dimethoxyanthraquinone (ref.190). 

The polyoxy tetrahydronaphthalene (in the epipodophyllotoxin series) readily formed an 0-glucoside in 74% yield with 3,4,6-tri-0-benzylglucosyl-2-benzyloxycarbonylamino-D-glucosephosphorodiamidate in dichloromethane containing boron trifluoride-etherate and 4A molecular sieve during 15mins. at -8X (ref.45). 

In a comprehensive study of 2-multiprenylphenols which are involved as biosynthetic precursors of ubiquiniones, three approaches were adopted (ref.6). In the first, to avoid 4-substitution found in acid-catalysed reaction of phenol, a blocking 4-methoxycarbonyl group was used. Thus reaction of methyl 4-hydroxybenzoate with phytol in dioxane containing boron trifluoride etherate at 50°C afforded a low yield of methyl 4-hydroxy-2-phytylbenzoate which upon hydrolysis and decarboxylation gave 2-phytylphenol. 

In the second approach (B), because of a low initial yield in the first method, the acid-catalysed reaction of the phenol in dioxane containing boron trifluoride etherate with the prenyl alcohol was used. In this way 2-geranyl, 2-farnesyl, 2-phytyl and 2-nonaprenylphenol were obtained in unstated yields, accompanied by the 4-isomer in each case. In the third strategy (C) the prenyl bromide was... 

Acid-catalysed rearrangement of meranzin in DMSO containing boron trifluoride etherate at 100°C produced isomeranzin (30%) and racemic auroptenol, oxidation of which with manganese dioxide in benzene afforded murrayone. 

Catalytic polymerization was performed in the presence of a designed composite catalytic system containing boron trifluoride-anisole complex and metaphosphoric acid for benzonitrile under a nitrogen atomosphere. The reaction temperature was lowered to about 200 C and the polymer obtained was linear and soluble, without any trace of cyclic trimers, a by-product described in the literature. But the molecular weight was in the range 1400-1700, with no obvious variation under different polymerization conditions. 

Both in dioxane containing sulfuric acid [47] or in water with molybdenum trioxide [48] hydrogen peroxide reacts with tri-O-acetyl-D-glucal to give 50-70% yields of the crystalline hydroperoxide 29. On the other hand, m-chlo-roperbenzoic acid in dichloromethane containing boron trifluoride gives peroxide 30, which spontaneously loses the benzoic acid to afford the unsaturated lactone 31 [49]. 

Simple thermal rearrangement of tri-O-acetyl-o-glucal, or treatment in benzene containing boron trifluoride [50], or heating in acetic anhydride containing nickel(II) chloride [51], all result at equilibrium not just in the expected 2,3-unsaturated glycosyl acetates 32 (65%) but in some of the starting material (15%) and its C-3 epimer tri-O-acetyl-D-allal 33 (20%) (Scheme 12). 

The dimerization of ethylene is selectively catalyzed by halotrisftriphenyl-phosphine)Co(I) in halobenzene containing boron trifluoride etherate [144,145]. The catalytic activity is significantly affected by the solvent, bromobenzene being the most effective. The rate of ethylene absorbtion decreases in the order bromobenzene > iodobenzene > o-dichlorobenzene > chlorobenzene > o-chlorotolene. The optimum ratio of boron to cobalt for the borontrifluoride etherate/bromo-tris(triphenylphosphine)Co(I) system is 1. This suggests a strong 1 1 interaction between the two components ... 

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