Showing papers on "Boron trifluoride published in 2002"

A Direct Method for the Conversion of Terminal Epoxides into γ-Butanolides

Abstract: A new and efficient process for the conversion of terminal epoxides to gamma-butanolides is described involving Lewis acid promoted epoxide ring-opening by 1-morpholino-2-trimethylsilyl acetylene. Addition of a terminal epoxide to a solution of the ynamine and boron trifluoride diethyl etherate in dichloromethane at 0 degrees C rapidly affords a cyclic keteneaminal that can be hydrolyzed and protodesilylated under mild conditions to provide the corresponding gamma-butanolide in high yield. The net transformation is equivalent to an acetate enolate opening of terminal epoxides. The formation of a cyclic keteneaminal as the direct addition product was observed by monitoring of the reaction by IR and NMR spectroscopy. Functionalized gamma-lactones were prepared by the interception of the reactive cyclic keteneaminal prior to hydrolysis. Reactions with enantiomerically enriched terminal epoxides provide the corresponding gamma-butanolides without loss of optical activity. The compatibility of the present methodology with a wide range of functional groups is noteworthy.

Formation of a Surface-Mediated Donor−Acceptor Complex: Coadsorption of Trimethylamine and Boron Trifluoride on the Silicon (001) Surface

Abstract: The interaction of trimethylamine and boron trifluoride on the Si(001) surface has been investigated using X-ray photoelectron (XP) spectroscopy. XP spectra show the TMA forms a dative bond with the clean Si(001) surface, while on the clean surface BF3 bonds dissociatively, yielding Si−BF2 and Si−F species. If the surface is first “saturated” with TMA, however, BF3 will continue to adsorb, giving rise to new F(1s) XP peaks. Based on an analysis of the energies and thermal behavior of these peaks, we propose that the adsorption of TMA and BF3 on the Si(001) surface leads to the formation of a novel surface-mediated donor−acceptor complex of the structure TMA−Si−Si−BF3.

Multicomponent reactions involving 2-methyleneaziridines: rapid synthesis of 1,3-disubstituted propanones.

Abstract: Ring opening of 1-alkyl-2-methyleneaziridines 1 or 2 is accomplished with organocopper reagents (R 2 CuLi or RMgX/CuI) in the presence of boron trifluoride diethyl etherate giving 1-substituted propan-2-ones 3-9 in 42-88% yield. Ring opening with RMgCl/CuI in the absence of the Lewis acid allows further alkylation of the metalloenamine (metalated imine) intermediate in a regiocontrolled manner. The sequential formation of two new intermolecular carbon-carbon bonds in this reaction provides a rapid entry into a variety of 1,3-disubstituted propan-2-ones, including 11 and 14-23. The scope and mechanism of this multicomponent reaction (MCR) has been assessed. It is established that this MCR tolerates alkyl, aryl, and benzylic Grignard reagents and a wide range of electrophiles, including alkyl iodides, bromides, and tosylates, as well as epoxides and aldehydes. In addition, gem-dimethyl substitution on the exocyclic double bond of the 2-methyleneaziridine is tolerated. This MCR has been applied to the one-pot synthesis of (Z)-6-heneicosen-11-one, 25, an important sex attractant of the Tussock moth. Using 3-deuterio-1-(1-phenylethyl)-2-methyleneaziridine, 26, we determined that this MCR occurs predominantly by direct ring opening at the sp 3 -hybridized aziridine carbon atom (C-3).

Electrochemical Polymerization of Thianaphthene in Mixed Electrolytes of Boron Trifluoride Diethyl Etherate and Trifluoroacetic Acid

Abstract: Substrate-supported polythianaphthene (PTN) films have been electrochemically synthesized by direct oxidation of thianaphthene on platinum or stainless steel electrode in mixed electrolytes of boron trifluoride diethyl etherate (BFEE) and trifluoroacetic acid (TFA). The oxidation potentials of the monomer in these media are considerably lower than those in neutral solvents. Increasing the content of TFA in the mixed electrolytes can effectively decrease the oxidation potential and increase the coupling rate of the monomer. On the other hand, a high TFA concentration can result in a negative effect on the properties of the as-formed polymer. The mixed electrolyte of BFEE + 16.7% TFA was found to be the most suitable medium for the electrosyntheses of PTN. PTN in dedoped state is soluble in usual strong polar organic solvent such as dimethyl sulfoxide (DMSO). Fluorescent spectral studies indicate that the polymer is a blue light emitter.

Multigram scale synthesis of a useful aza-Diels–Alder adduct in a one-step procedure

Abstract: The aza-Diels–Alder reaction between a chiral imine (derived from methyl glyoxylate and ( S )-(−)-1-phenylethylamine) and cyclopentadiene, in the presence of trifluoroacetic acid and boron trifluoride diethyl etherate have been performed in a one-step procedure. Without isolation of intermediates, 111.5 g of the major exo -isomer was isolated in a total yield of 56% using a protocol where extensive chromatography was not required.

Cationic Ring-Opening Polymerization of Five-Membered Cyclic Thiocarbonate Bearing an Adamantane Moiety via Selective Ring-Opening Direction

Abstract: A novel five-membered cyclic thiocarbonate bearing adamantane moiety, 4,6-dioxatetracyclo[6.3.1.1.3,1003,7]tridecane-5-thione (1), was synthesized from 1,2-adamantanediol and thiophosgene in the presence of pyridine. Monomer 1 underwent cationic ring-opening polymerization initiated by triethyloxonium tetrafluoroborate (Et3OBF4), methyl trifluoromethanesulfonate (TfOMe), trifluoromethanesulfonic acid (TfOH), and H2O with 2 mol % of boron trifluoride etherate (BF3OEt2) in CH2Cl2 at 30 °C to afford the polythiocarbonate by isomerization of the thiocarbonyl group into a carbonyl group with selective ring-opening direction. The number-average molecular weight and polydispersity of the polymer obtained by polymerization with H2O/BF3OEt2 were 10 600 and 1.44, respectively. The temperature with 5% weight loss of the obtained polymer was 338 °C. Monomer 1 expanded as large as 14% during the polymerization.

Synthesis and properties of peroxy derivatives of epoxy resins based on Bisphenol A: Effects of the presence of boron trifluoride ethereate

Abstract: Oligomers containing peroxy groups have been synthesized on the basis of epoxides reacting with tert–butylhydroperoxide in the presence of boron trifluoride etherate. Dependence of reaction rates upon the quantity of catalyst, temperature and also nature of hydroperoxide has been investigated: A kinetic equation for the process has been formulated and also a kinetic scheme for the reaction taking into account the presence of boron trifluoride etherate is proposed. Structures of the synthesized peroxy oligomers have been confirmed by IR- and NMR-spectroscopy. The reaction initiating properties of the oligomers so synthesized were studied using as the example the styrene polymerization reaction.

Electrosynthesis of free‐standing poly(para‐phenylene) films in mixed electrolytes of boron trifluoride diethyl etherate and trifluoroacetic acid on stainless steel electrode

Abstract: Free-standing poly(para-phenylene) (PPP) films have been electrosynthesized by direct oxidation of benzene on stainless steel electrode in mixed e1ectrolytes of boron trifluoride diethy1 etherate (BFEE) and trifluoroacetic acid (TFA). The oxidation potential of the monomer in these media is lower than those in the neutral media. Increasing the content of TFA in the mixed electrolyte can effective1y decrease the oxidation potential and increase the coup1ing rate of the monomer. The films obtained from these media were very shiny and flexible, and could easily be processed into various shapes by conventional mechanical methods. The films had a 1inear chain structure, and their degree of polymerization could be improved by increasing the TFA content in the mixed electrolyte. Moreover, the films had a fairly good thermal stability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2462–2466, 2002

Chiral glycine cation equivalents: N-acyliminium species derived from diketopiperazines

Abstract: Studies towards a N,N′-bis(p-methoxybenzyl)diketopiperazine asymmetric glycine cation equivalent for the synthesis of homochiral α-amino acids are described. The oxidation of enolate 3 with molecular oxygen provides either a mixture of hydroxylated diketopiperazines 7 and 8 or trione 10 depending upon the reaction conditions. The nucleophilic reduction of trione 10 and the reaction of acetoxy N-acyliminium ion precursors 5 and 6, derived from 7 and 8, with allyltrimethylsilane and boron trifluoride etherate is examined and a model for the stereoselectivity observed in these additions is presented.

Stereoselectivity of Reactions at the Glycoside Center of Carbohydrates: VII. Synthesis of Aryl α- and -β-D-Glucopyranosides by Helferich, Catalyzed by Boron Trifluoride Etherate

Abstract: 13C NMR spectroscopy was used to study the stereoselectivity of glycosylation of phenols with the α and β anomers of penta-O-acetyl-D-glucopyranose, penta-O-trifluoroacetyl-D-glucopyranose, and 2,3,4,6-tetra-O-acetyl-1-O-trifluoroacetyl-D-glucopyranose in the presence of boron trifluoride etherate at varied temperature, time, and catalyst amount. The boron trifluoride etherate-catalyzed reaction of penta-O-acetyl-β-D-glucopyranose and 2,3,4,6-tetra-O-acetyl-1-O-trifluoroacetyl-β-D-glucopyranose with phenols occurs with a high stereocontrol to give, depending on conditions, predominantly 1,2-cis- or 1,2-trans-arylglycosides. This reaction can be used for preparative synthesis of the α- and β-anomeric forms of glycosides of a wide range of phenols.

3α-Fluoro Analogues of "Allopregnanolone" and Their Binding to GABAA Receptors

Abstract: (Diethylamino)sulfur trifluoride (DAST) was used for the preparation of 3α-fluorides ( e.g. , 3α-fluoro-5α-pregnane-12,20-dione, 3α-fluoro-16α-[(methoxycarbonyl)methyl]-5α-pregnan-20-one, methyl 3α-fluoro-5α-androstane-17β-carboxylate, 3α-fluoro-5β-pregnan-20-one) from the corresponding 3β-alcohols and for the preparation of 3,3-difluorides from 3-ketones ( e.g. , 3,3-difluoro-5α-pregnan-20-one). Boron trifluoride etherate was used for the conversion of an epoxide into 3α-fluoro-2β-hydroxy-5α-pregnan-20-one. The in vitro binding of the 3α-fluorides and the corresponding 3α-alcohols to the GABA A receptor was established using [ 3 H]muscimol and [ 35 S]- tert -butylbicyclo[2.2.2]phosphorothionate as ligands.

Method for continuous production of polyisobutene

Abstract: A process for the continuous preparation of polyisobutene having a number-average molecular weight {overscore (MN of from 500 to 50,000 and containing at least 50 mol % of terminal double bonds by one-stage or multistage, continuous polymerization of isobutene in the liquid phase in the presence of a catalyst comprising boron trifluoride and at least one oxygen-containing compound at below +40° C., wherein the liquid reaction phase has a viscosity of from 6 to 20 mm /s (determined according to DIN 51562), at least in the first polymerization stage, is described.

A Convenient Preparation of 4-Methyl- and 4-Phenylseleno-1,1,1-trihalo-3-alken-2-ones and their Usefulness in the Synthesis of 3-Trihalomethyl­isoselenazoles

Abstract: A convenient synthesis of fourteen 4-methyl- and 4-phenylseleno-1,1,1-trihalo-3-alken-2-ones [CX 3 C(O)CH=CR 1 SeR. where X = F, Cl; R = Me, Ph; and R 1 = H, alkyl, aryl from the reaction of the corresponding 4-methoxy-1,1,1-trihalo-3-alken-2-ones with methyl- or phenylselenols in the presence of boron trifluoride etherate is reported. The reaction of 4-methylseleno- 1,1,1-trihalo-3-alken-2-ones with bromine and ammonia lead to 3-trihalomethylisoselenazoles in good yields. The usefulness of the trichloromethyl group as a carboxyl group precursor was demonstrated by the conversion of 5-ethyl-3-trichloromethylisoselenazole to 5-ethyl-3-carboxyisoselenazole acid.

Simultaneous determination by GC-MS of epoxy and hydroxy FA as their methoxy derivatives

Abstract: We report on a capillary GC-MS method for the quantitative analysis of hydroxy and epoxy FA. Catalytic hydrogenation of lipid extracts produces stable saturated lipids. Saponification followed by methylation with boron trifluoride in the presence of methanol converts FA to methyl esters and epoxy groups to methoxy-hydroxy groups. These compounds are purified from nonoxidized methyl esters using solid phase extraction. Derivatization of the hydroxy group using tetramethylammonium hydroxide forms methoxy and vicinal dimethoxy FAME. When subjected to EI-MS, fragmentation gives two characteristic ion fragments for each epoxy and hydroxy positional isomer. Quantitative measurements were achieved using uniformly labeled hydroxy and epoxy 13C FA as internal standards. Epoxy and hydroxy FA were identified in both plasma and adipose tissue of men, and the levels of hydroxy and epoxy in these tissues were related. The levels of hydroxy isomers were typical of oxidation of linoleic acid, whereas epoxy isomers were characteristic of oxidation of oleic acid.

A Convenient and General Approach to Alkyl‐, Alk‐1‐enyl‐, and Aryldifluoroboranes

Abstract: A simple and general procedure, especially useful for the small scale preparation of alkyl-, alk-1-enyl-, and aryldifluoroboranes RBF2 was elaborated. Suspensions of the easily available and storable K [RBF3] salts undergo fluoride abstraction when treated with boron trifluoride to form solutions of the corresponding difluoroboranes RBF2.

Crossed pinacol coupling reaction between aldehydes and imines: A rapid access to 1,2-amino alcohols

Abstract: In the presence of zinc, boron trifluoride etherate, and methyltrichlorosilane, aldehydes and imines underwent a crossed pinacol coupling reaction to give 1,2-amino alcohols in good to excellent yields.

METHOD FOR PRODUCING α-SUBSTITUTED ACRYLIC ACID NORBORNANYLS

Abstract: PROBLEM TO BE SOLVED: To provide a method for synthesizing a norbornene-based resist monomer, suitable for production in industrial scale. SOLUTION: An α-substituted acrylic acid is directly reacted with a substituted norbornene. The reaction is preferably carried out in the presence of an acid catalyst. At least one kind of compound selected from a group consisting of phosphoric acid, sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, boron trifluoride, titanium tetrachloride and tin tetrachloride is preferably used as the acid catalyst. According to the present invention, treatment of the reaction mixture is remarkably facilitated, because the reaction mixture is kept in a low viscosity through reaction and purification processes. COPYRIGHT: (C)2004,JPO

Synthesis of highly hindered oxepins and an azepine from bis-trityl carbenium ions: structural characterisation by NMR and X-ray crystallography

Abstract: Reactions of the bis-carbenium ion 2,2′-bis[bis(p-methoxyphenyl)methyl]biphenyl ditetrafluoroborate with ammonia, n-propylamine and benzylamine have been studied with the aim of developing an acid-labile protecting group for primary amines that masks both hydrogen atoms of the NH2 group. Although the parent 5,5,7,7-tetrakis(p-methoxyphenyl)-5,7-dihydrodibenzo[c,e]azepine was isolated and fully characterised, the corresponding azepines could not be obtained in a pure state from the reactions with the primary amines. The bis-carbenium ion was prepared from the treatment of 2,2′-bis[bis(p-methoxyphenyl)hydroxymethyl]biphenyl with fluoroboric acid. Attempts to prepare the corresponding diphenyl analogue were unsuccessful using either fluoroboric acid or boron trifluoride. The only product isolated from these reactions was 5,5,7,7-tetraphenyl-5,7-dihydrodibenzo[c,e]oxepin. The oxepin and its phenyl-p-methoxyphenyl and bis(p-methoxyphenyl) analogues were efficiently obtained by dehydration of the corresponding diol, e.g. 2,2′-bis[bis(p-methoxyphenyl)hydroxymethyl]biphenyl, in the presence of 3 A molecular sieves or Amberlite IR-200 resin. The compounds 2,2′-bis[bis(p-methoxyphenyl)hydroxymethyl]biphenyl, (R,R/S,S)-2,2′-[bis(phenyl-p-methoxyphenyl)hydroxymethyl]biphenyl, 5,5,7,7-tetraphenyl-5,7-dihydrodibenzo[c,e]oxepin, 5,5,7,7-tetrakis(p-methoxyphenyl)-5,7-dihydrodibenzo[c,e]oxepin and 5,5,7,7-tetrakis(p-methoxyphenyl)-5,7-dihydrodibenzo[c,e]azepine were characterised by crystal structure analyses. 2,2′-Bis[bis(p-methoxyphenyl)hydroxymethyl]biphenyl and 5,5,7,7-tetrakis(p-methoxyphenyl)-5,7-dihydrodibenzo[c,e]oxepin exhibited dynamic NMR properties, and free energy barriers have been determined.

Lewis Acid Catalyzed Synthesis of 4-Aminopyrrolo[1,2-a]quinolin-5-ol Derivatives from 2-(1-Pyrrolyl)benzaldehyde and Isocyanides

Abstract: Reaction of 2-(1-pyrrolyl)benzaldehyde with isocyanides in the presence of a catalytic amount of boron trifluoride diethyl etherate was followed by treatment with acetic anhydride in pyridine to give the corresponding O-acetyl derivatives of 4-alkyl(or aryl)aminopyrrolo[1,2-a]quinolin-5-ols in moderate yields.

Living radical and cationic polymerizations in water and organic media

Abstract: This lecture will focus two living polymerizations that can be carried out in water as well as in organic media. The first one is transition metal-catalyzed living radical polymerization, for which Ru(II) and other transition metals play a critical role to control the process; for aqueous systems, Ru(II) and Fe(II) half metallocene complexes are useful. The second is cationic polymerization with water-tolerant Lewis acids as catalysts, including rare earth triflates and boron trifluoride for selected monomers. Discussion will be directed to the design of initiating systems, search of versatile catalysts, and precision synthesis of new polymers.