Showing papers on "Boron trifluoride published in 1989"

Oxidative Grob Fragmentation of γ-Tributylstannyl Alcohols with a Combination of Iodosylbenzene, Dicyclohexylcarbodiimide, and Boron Trifluoride.

Abstract: Methode de fragmentation utilisant la combinaison MOPMO (modified Pfitzner-Moffatt conditions). La fragmentation, combinee a une addition conjuguee de tributylstannyllithium et une reduction ou une alkylation est un procede efficace d'ouverture reductrice et alkylante du cycle de cetones cycliques vinyliques. Les produits sont des composes carbonyles insatures d'une stereochimie determinee

Process for manufacture of olefin oligomer

Abstract: A process for the manufacture of an olefin oligomer, comprising the steps of polymerizing an olefin monomer in the presence of boron trifluoride and a boron trifluoride-alcohol complex as catalysts, to prepare a first oligomerization product, and then carrying out one of following steps (a) to (c): (a) removing boron trifluoride from the above first product by (i) placing the product under a reduced pressure, (ii) blowing an inert gas into the product, or (iii) heating the product at a relatively low temperature, to thereby prepare a second oligomerization product, and then subjecting the second product to a precipitation treatment to separate the boron trifluoride-alcohol complex therefrom, (b) heating the above first product at a relatively elevated temperature to recover boron trifluoride, or (c) centrifuging the above first product to recover the boron trifluoride-alcohol complex. These steps allow the catalysts to be recovered while maintaining the activity thereof at a desired level.

Total Synthesis of Silychristin, an Antihepatotoxic Flavonolignan

Abstract: The total synthesis of silychristin, an antihepatotoxic flavonolignan, is described. The key intermediate, the transdihydrobenzofuran (15) was synthesized as follows. Treatment of the chalcone epoxide (9) with boron trifluoride etherate and subsequent reduction with sodium borohydride gave exclusively the erythro-1, 2-diaryl-1, 3-propanediol (10). Hydrogenolysis of 10 with hydrogen over a palladium catalyst followed by cyclization of the debenzylation product (13) with boron trifluoride etherate in acetic acid afforded 15 as a single product.

Process for recovering boron trifluoride from an impure gaseous boron trifluoride residue

Abstract: The present invention provides a process for recovering boron trifluoride from an impure gaseous boron trifluoride residue. The process comprises: (a) feeding an impure gaseous boron trifluoride residue containing sulfur dioxide as an impurity into a mixture of boric and sulfuric acids wherein the acid mixture absorbs boron trifluoride from the impure boron trifluoride residue and slightly absorbs or does not absorb sulfur dioxide from the impure gaseous boron trifluoride residue; and (b) removing the unabsorbed sulfur dioxide from the acid mixture. The present invention also provides a boron trifluoride preparation and purification process. The process comprises the steps of (a) reacting boric acid and fluorosulfuric acid in sulfuric acid to form a product; (b) distilling the product from step (a) to yield pure boron trifluoride and impure gaseous boron trifluoride; (c) feeding the impure gaseous boron trifluoride residue containing sulfur dioxide as an impurity into a mixture of boric and sulfuric acids wherein the acid mixture absorbs boron trifluoride from the impure gaseous boron trifluoride residue and only slightly absorbs sulfur dioxide from the impure gaseous boron trifluoride residue; and (d) removing the unabsorbed sulfur dioxide from the acid mixture. The recovered boron trifluoride may be used as a catalyst.

Boron Trifluoride-Assisted Alkylation of 2-Isoxazolines. A Novel Route to N-Unsubstituted Isoxazolidines

Abstract: In the presence of boron trifluoride, 2-isoxazolines undergo the addition of organolithiums to afford N-unsubstituted isoxazolidines in moderate to good yields.

Radiative versus three-body addition in halide ion reactions with boron trifluoride and boron trichloride over the temperature range 220-410 K

Abstract: Etude du mecanisme de reaction ion-molecule en fonction de la temperature et de la pression

Radiotracers in fluorine chemistry. Part 12. Reactions between caesium fluoride and arsenic pentafluoride, boron trifluoride, sulphur tetrafluoride, carbonyl fluoride, and carbon dioxide under heterogeneous conditions at room temperature. Radiotracer studies using fluorine-18, sulphur-35, and carbon-14

Abstract: Activation of CsF by thermal decomposition of its 1 : 1 adducts with hexafluoroacetone or carbonyl fluoride results in significantly greater activity with respect to its reactions with AsF5, BF3, and SF4 under heterogeneous conditions at room temperature, and enables reactions involving carbonyl fluoride and carbon dioxide to be studied. The results of radiotracer experiments employing 18F and 35S or 14C are consistent with the occurrence of weakly adsorbed SF4 or F2CO at the surface of activated CsF in addition to permanently retained species SF5– and F3CO–. Carbon dioxide interacts weakly with activated CsF. Room-temperature 18F exchange occurs between 18F-labelled F2CO and activated CsF. It is not observable in the other systems but does occur at 373 K. It is suggested that the CsF activation process results in a pore structure for the solid and that this is responsible for its increased reactivity.

Stereoselective Synthesis of 2-Thioglycosides of N-Acetylneuraminic Acid.

Abstract: Treatment of methyl 5-acetamido-2,4,7,8,9-penta-O-acetyl-3,5-dideoxy-β-d-glycero-d-galacto-2-nonulopyranosonate (1) severally with thiophenol, phenylmethanethiol, and ethanethiol in the presence of boron trifluoride etherate gave the corresponding 2-thio-β-glycosides 3–5. Treatment of methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-β-d-glycero- d-galacto-2-nonulopyranosyl chloride)onate (2) severally with thiophenol in the presence of N,N-di-isopropylethylamine, O-ethyl S-potassium dithiocarbonate, and O-ethyl S-potassium thiocarbonate gave the corresponding 2-thio-α-glycosides 7, 10, and 11, of which 10 was converted into the ethyl 2-thio-α-glycoside 9 on heating with N,N-dimethylformamide-sodium iodide. The phenyl 2-thioglycosides 3 and 7 were converted into the corresponding sulfones.

Method for producing "poly-N-butene oils" from C4-fraction residues

Abstract: The method consists in the polymerization of olefins with a prevailing content of 1-butene and cis- and trans-2-butenes in the mixture of hydrocarbons known as rafinate II, which is derived from the C₄-fractions after separation of 1,3-butadiene and isobutylene, under initiation with boron trifluoride (BF₃) or alkylaluminium chlorides with the general formulae R₂AlCl and RAlCl₂ (in which each R represents a C₁ to C₆-alkyl group) in the presence of hydrogen chloride (HCl), hydrogen fluoride (HF), or organic compounds with a reactive chlorine or fluorine bonded to a tertiary-, benzyl- or allyl-carbon atom, as coinitiators. The method according to the solution may be carried out in such a way, that rafinate II derived from the production of methyl tert-butyl ether or from the selective polymerization of isobutylene, in which 1-butene present in a concentration at least 20% is polymerized together with cis- and trans-2-butenes present in a concentration of at least 15%, at a temperature of +100°C to -70°C, to form to oily products with molar mass M n = 300 to 1200. Preferably the mixture derived as rafinate II from the production of methyl tert-butyl ether is first freed of methanol to the content lower than 300p ppm.

Synthesis of the 1H,5H-Naphtho[1,8-ef][1,3]dithiocin System

Abstract: The titled new pericyclized naphthalene system has been prepared in four steps from 1,8-naphthalenedicarboxylic anhydride in an overall yield of 35–78% The key step in the synthesis employed a dithioacetal-cyclization reaction of 1,8-bis(mercaptomethyl)naphthalene with carbonyl compounds using boron trifluoride etherate as a catalyst

Polymerization of 2-phenyl-aziridine A kinetic study

Abstract: The ring-opening polymerization of 2-phenyl aziridine was studied with several catalyst systems: boron trifluoride etherate, chlorhydric acid, perchloric acid, dimethyl sulfate and methyl triflate. The corresponding polyamine was obtained as a pale yellow solid with a number average molecular weight around 2,000–3,000. A kinetic study is discussed in the case of perchloric acid and methyl triflate.

Preparation of oxymethylene copolymer

Abstract: PROBLEM TO BE SOLVED: To obtain a copolymer comprising oxyalkylene units which is highly deactivated and exhibits a good color tone by bulk-polymerization of a mixture of trioxane with a cyclic ether in the presence of a polymerization catalyst based on boron trifluoride and subsequently deactivating the catalyst with a nitrogen compound, such as an amine and the like, having a specific chemical structure: SOLUTION: As cyclic ethers to be copolymerized with trioxane, there can be mentioned ethylene oxide, dioxolane, phenyl glycidyl ether and the like. These compounds are co-polymerized in an amount of 0.1-10 mole %, preferably 0.2-5 mole %, based on trioxane. As the polymerization catalyst is employed boron trifluoride, boron trifluoride hydrate or a coordination compound of an organic compound having O or S atom with boron trifluoride as an organic solvent solution. The nitrogen compound for the deactivation of the catalyst after the bulk polymerization is represented by the formula (wherein R are each H or 1-5C alkyl; and R is 1-10C alkylene) and is employed in an amount such that the number of the boron atoms in the polymerization catalyst is equal to or more than the number of nitrogen atoms therein. After the deactivation of the catalyst, the polymer is heated to 100-270 deg.C to give the product.

Electrophilic addition of 4′-nitrobenzenesulphenanilide to alkynes in acetic acid. A synthesis of β-acetoxyvinyl sulphides

Abstract: 4′-Nitrobenzenesulphenanilide reacts at room temperature with simple alkyl- and aryl-alkynes in acetic acid in the presence of boron trifluoride–diethyl ether to afford products of acetoxysulphenylation in moderate to good yields. The addition products are generally produced with trans-stereospecificity and in a regioselective fashion (Markovnikov orientation). The findings are consistent with a mechanism involving intermediary of thiirenium ions which would result from alkyne attack at the sulphur atom of the anilide complexed with boron trifluoride.