Triethylamine boron trifluoride

Elimination of hydrogen chloride from 2/f perfluoro-2-methylpropane-1 -sulfenyl chloride by the triethylamine-boron trifluoride complex results in cyclization to perfluoro-l,l-dimethylthiirane (perfluoroisobutylene sulfide) [, 9] (equation 9)... 

Dehydrofluorination of 2,4,4,4-tetrafluoro-l-phenyl-3-(trifluoromethyl)but-l-ene (8) by the triethylamine-boron trifluoride complex gives the buta-1,3-diene 9.48... 

Elimination of hydrogen fluoride from vinylic fluoride 16. using the triethylamine-boron trifluoride complex, yields the allene 17.96... 

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 dehydration of thiobenzoylthioglycolic acid (135, R = Ph, R = H) with acetic anhydride-boron trifluoride was initially described as yielding the meso-ionic l,3-dithiol-4-one (134, R = Ph, R = H), but subsequent studies showed that the product was in fact the 5-substituted derivative 134, R = Ph, R = COCHjSCSPh. Authentic meso-ionic l,3-dithiol-4-ones (134) have recently been prepared (85-90% yield) by the cyclodehydration of the acids (135) with acetic anhydride-triethylamine at 0°-10°. Examples include anhydro-4-hydroxy-2-phenyl-l,3-dithiolium hydroxide (134, R = Ph, R = H) described as scarlet needles, m.p. 113°—115° this compound is sensitive to moisture. Anhydro-4-hydroxy-2,5-diphenyl-1,3-dithiolium hydroxide (134, R = R = Ph) was obtained as gold lustered, deep violet needles,... 

Hydrolysis of the ethyl ester proceeded smoothly using hydrochloric acid in acetic acid to give carboxylic acid 69 in 88% yield (Scheme 4.9). Previously, amines were allowed to react with the carboxylic acid core in hot DMSO to deliver the C7 products however, the difluoroborate 70, derived from the carboxylic acid 69, greatly increased the reactivity of the C7 position. Consequently, the displacement of the C7-F with amines was accomplished at lower temperature (Baker et al., 2004 Cecchetti et al., 1996 Domalaga et al., 1993 Ellsworth et al., 2005a,b Hu et al., 2003). In this event, the carboxylic acid was allowed to react with boron trifluoride to deliver difluroboronate 70 in excellent yield. The thus afforded borate ester reacted with A -methylpiperidine in DMSO in the presence of triethylamine at ambient temperature to furnish ( —)-ofloxacin (1, levofloxacin) in 56% yield. 

The olefins formed under these conditions using other tertiary alcohols tend to follow the Hofmann rule [6a]. However, tertiary alcohols and phenols [6b] can be made to react with isocyanates to give urethanes when they are catalyzed by acids or bases such as pyridine [6b], triethylamine, sodium acetate, boron trifluoride etherate, hydrogen chloride, or aluminum chloride [7]. Table I indicates the results of preparing phenylurethanes of tertiary alcohols... 

Methyl perfluoromethacrylate reacts with allyl and propargyl alcohols to give the Michael addition products 19 and 20, respectively these eliminate hydrogen fluoride in the presence of the boron trifluoride-triethylamine complex and rearrange to acyl fluorides 21 and 22. Hydrolysis of the acyl fluorides with base results in decarboxylation to give the 2-(trifluoromethyl) esters 23 and 24.11... 

The combination of triethylamine with boron trifluoride has been described as a useful reagent for dehydrofluorinations, e.g. formation of 12,36 or 13.35... 

With triethylamine in methanol, 1,3-dimethylbarbituric acid (217) adds DMAD in Michael fashion to give 218, which, after heating to 170° or treatment with boron trifluoride etherate at 120° to 130° gave pyrano[2,3-[Pg.384]

Boron trifluoride diethyl etherate Tetrabutylammonium hydroxide Triethylamine Tris(3,6-dioxahepyl)amine... 

Boron trifluoride diethyl etherate Sodium bicarbonate Palladium on charcoal Sodium periodate Hydroperoxide, 1,1-dimethylethyl Titanium tetraisopropoxide Ethyl diisopropylamine Triethylamine Ammonium sulfate Trimethylsilyl triflate d-3-oxo-a-D-gluco-pyranoside -oxo-a-D-erythro-hexopyranoside... 

Intermolecular cyclization of 424 with dimethoxypropane in the presence of boron trifluoride afforded the acetonide 425 (84%) <1996TL2467>. Chlorination of the reactive methane group in 426 with trifluoromethanesul-fonyl chloride and treatment of the product with triethylamine gave the tricyclic azetidinone 427 <1999T8039>. 

Dehydration of primary nitroalkanes with phenyl isocyanate or acetic anhydride in the presence of catalytic triethylamine affords nitrile oxides, which may be trapped as their 1,3-dipolar cycloadducts or allowed to dimerize to the corresponding furoxans. Other dehydrating agents that have been used include diketene, sulfuric acid and, when the a-methylene group is activated by electron-withdrawing groups, boron trifluoride in acetic anhydride, trifluoroacetic anhydride with triethylamine, and nitric acid in acetic acid. 

It has been shown (76JOC1724) that a previously described compound (65BCJ596), prepared by treatment of thiobenzoylthioglycollic acid (264) with acetic anhydride in the presence of boron trifluoride, is indeed the acylated 1,3-dithiolone (265) and not the claimed 2-phenyl-l,3-dithiolylium-4-olate. The latter can be prepared from thiobenzoylthioglycollic acid (264) and acetic anhydride-triethylamine (76JOC1724) or acetic anhydride-dicyclohexyl-ethylamine (76CB740). 

Olefins react with benzenetellurinyl trifluoroacetate in acetonitrile in the presense of boron trifluoride etherate to give 2-acetaminoalkyl phenyl tellurium oxides that are converted, upon treatment with triethylamine in tetrahydrofuran at 30° for 4 h, to 4,5-dihydro-l,3-oxazoles4. These highly regio- and stereoselective reactions allow the one-pot, high-yield conversion of olefins to 1,3-oxazoles. Ethyl cyanide and phenyl cyanide can be used instead of acetonitrile. 

B. 3-(1,1-Dimethylethyl) 4-methyl-(S)-2,2-dimethyloxazolidine-3,4-dicarbox-ylate (3). To a solution of N-Boc-L-serine methyl ester (10.0 g, 45.6 mmol) in acetone (165 mL) is added 2,2-dimethoxypropane (50 mL, 400 mmol) and boron trifluoride etherate (BF3-OEt2, 0.35 mL, 2.8 mmol) (Notes 9 and 10). The resulting orange solution is stirred at room temperature for 2.5 hr when TLC analysis indicates the reaction to be complete (Note 11). The reaction mixture is treated with 0.9 mL of 99% triethylamine and the solvent is removed under reduced pressure. The residual brown syrup Is partitioned between diethyl ether (150 mL) and saturated aqueous sodium bicarbonate solution (250 mL). The aqueous layer is extracted with diethyl ether (2 x 150 mL) and the combined organic phases are dried with anhydrous sodium sulfate and concentrated under reduced pressure (7 mm and 65°C bath temperature) to give 10.4-10.8 g (88-91% crude yield) of oxazolidine methyl ester 3 as a pale yellow oil (Note 12). Analysis of crude 3 by 1H NMR indicates a chemical purity of > 95%. The product can be used without further purification. 

Mixed carboxylic-carbonic anhydrides decompose in the presence of DMAP to give esters and carbon dioxide under mild conditions [Scheme 6,51], In the case of benzyl esters, the mixed car boxy lic-car bon ic anhydrides can be generated by reaction of the carboxylic acid with benzyl chloroformate in the presence of triethylamine (1.1 equiv) and DMAP (0.1 equiv)126 or more conveniently by reaction of the carboxylic acid with dibenzyl dicarbonate (dibenzyl pyrocarbo-nate) in THF or ferf-butyl alcohol in the presence of DMAP (0.1 equiv).127 The reactions generally work well except for hindered carboxylic acids. The method can also be used to make methyl, ethyl, ferf-butyl and ally esters. Carboxylic acids react with 2 equivalents of benzyl 2,2t2-trichloroacetimidate12s in the presence of a catalytic amount of boron trifluoride etherate to give the benzyl ester in modest to good yield,12g... 

Boron trifluoride-triethylamine effects a ring-opening elimination of 4,4-difluoro-3-trifluoromethyl-l,2-oxathietane 2,2-dioxide to give fluorosulfonyl-trifluoromethylketene. Eliminations occur from intermediate 3-sultones, obtained by addition of sulfur trioxide to alkenes, to give alkenesulfonic acids. ... 

Cyclodehydration of a-(thioaroylthio)- or a-(thiocarbamoylthio)carboxylic acids (96) with acetic anhydride in the presence of catalytic amounts of boron trifluoride etherate, or with a mixture of acetic anhydride and triethylamine (1 1), leads to the 2-aryl- or 2-amino-l,3-dithiolium-4-olates (97) listed in Table VIII.Chemical properties, dipole moments, NMR, IR, and UV spectra, and charge distribution calculations are consistent with a mesoionic structure. " ... 

Esterification Alumina. Boron trifluoride. Diazomethane. Dimethylformamide dimethyl acetal. Dimethylformamide dineopentyl acetal. Dimethyl sulfite. Diphenyidiazomethane. Ethyldicyclohexylamine. Ion-exchange resins. Isobutene. Methanesulfonic anhydride. 3 % Methanolic HCl (see Acetyl chloride). Methyl iodide. l-Methyl-3-p-tolyltriazine. Poly-phosphoric acid. Sulfosalicylic acid. Sulfuryl chloride. p-Toluenesulfonic acid. p-Tpluene-sulfonyl chloride. Triethylamine. Triethylorthoformate. Trifluoroacetic anhydride. Esterification of phosphoric acid Trichloroacetonitrile. 

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