Presence Of Trifluoromethanesulfonic Acid Research Articles

Comments on “Mathematical Description of Isobutane Alkylation with Butenes in the Presence of Trifluoromethanesulfonic Acid”

Comments on “Mathematical Description of Isobutane Alkylation with Butenes in the Presence of Trifluoromethanesulfonic Acid”

Mathematical Description of Isobutane Alkylation with Butenes in the Presence of Trifluoromethanesulfonic Acid

Isobutane alkylation with 2-butene kinetics was studied in the presence of trifluoromethanesulfonic acid (TfOH) catalyst. The rate of this reaction is very fast and strongly dependent on acidity. Therefore, the study was conducted in the presence of compounds able to decrease the acidity (acidity controllers) and thereby to decrease the reaction rate to measurable values. The butene surplus and the reaction byproduct, acid-soluble oil (ASO), were used as acidity controllers. The rate of isooctane sum accumulation was studied in the wide variation range of reactant concentrations (from acid surplus to butenes up to a butene surplus) at temperatures from −20 to −45 °C. On the basis of the physicochemical and kinetic studies, the mechanism was suggested for the reaction predominantly proceeding in the acidic phase. The kinetic equations obtained adequately describe the main reaction routes including isooctanes and ASO formation. All route rate equations are first order on the activity of proton in the acidic phase. The effective route activation energies were determined.

Stereoselective Mannich‐Type Reaction of Chiral Aldimines with 2‐Silyloxybutadienes by Using Trifluoromethanesulfonic Acid.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Stereoselective Mannich-type reaction of chiral aldimines with 2-silyloxybutadienes by using trifluoromethanesulfonic acid

Novel stereoselective Mannich-type reaction of chiral aldimines with 2-silyloxybutadienes in the presence of trifluoromethanesulfonic acid has been carried out to give the corresponding products, which are not obtained by general Lewis acid-promoted methods, with 70–92% de in 62–74% yield. No cycloadducts were detected in the crude product by 1H NMR.

A Change of Face

CHEMISTRY In the Diels-Alder reaction, an alkene reacts with a diene to form a six-membered ring. A variety of stereochemical outcomes are possible with substituted reactants, and substituent groups can deactivate the reaction. Thus, the search for general catalysts of this reaction continues. Recently, Corey et al . reported a route in which proline-derived oxazaborolidines, in the presence of trifluoromethanesulfonic acid (TfOH), produce a strong Lewis acid that enables even α,β-unsaturated aldehydes to react efficiently and with stereochemical control. Often, such routes are not general, but Ryu et al . show that these catalysts can direct the reaction of even weaker dieneophiles, such as acrylic acid and ethyl vinyl ketone, with cyclopentadiene both in high yield and with high enantiomeric excess. The pretransition-state complex in these latter reactions ( 4 ) differs in face selectivity from that for the α,β-unsaturated aldehydes ( 3 ) in terms of the hydrogen bonds formed. — PDS J. Am. Chem. Soc. 124, 3808 (2002); J. Am. Chem. Soc. 10.1021/ja027468h.

Bis(trifluoromethane)sulfonimide initiated ring-opening polymerization of octamethylcyclotetrasiloxane

Polymerization of octamethylcyclotetrasiloxane in the presence of hexamethyldisiloxane and catalytic amounts of bis(trifluoromethane)sulfonimide (TFSI-H) under dry conditions at 25 or 100 °C gave α,ω-bis(trimethylsilyl)-polydimethylsiloxanes (PDMS) of a low molecular weight ( M ̄ n <13 000 g mol −1). The polymers are very similar to those obtained in the presence of trifluoromethane sulfonic acid as initiator but the polymerization initiated by TFSI-H was faster. Addition of the sufficient quantity of tributylamine to neutralize completely any acid suppressed the polymerization. No polymerization was observed in the presence of triflic anhydride (TfA), trimethylsilyl-bis(trifluoromethane)sulfonimide, trimethylsilyltriflate or the lithium salt of bis(trifluoromethanesulfonyl)imide.

Direct Preparation of Rotaxane from Aminoalcohol: Selective O-Acylation of Aminoalcohol in the Presence of Trifluoromethanesulfonic Acid and Crown Ether

Abstract Selective O-acylation of aminoalcohols by a bulky acid anhydride in the presence of trifluoromethanesulfonic acid and dibenzo-24-crown-8 afforded [2]rotaxane in high yields. An acid halide could be used as an acylating reagent in the presence of silver trifluoromethanesulfonate.

Changing the ortho/para ratio in aromatic acylation reactions by changing reaction conditions: a mechanistic explanation from kinetic measurements.

Kinetic measurements of the acylation of toluene (2a) and p-xylene (2b), side-chain deuterated toluene (2a-d(3)), as well as perdeuterated toluene (2a-d(8)) and p-xylene (2b-d(10)) with the aroyl triflate 1 in 1,2-dichloroethane reveal a strong dependence of the isotope effect on reaction conditions. In the presence of trifluoromethanesulfonic acid (HOTf), the second-order rate constants k(H)/k(D) observed are in the order of 1.75-1.94, whereas in the presence of 2,4,6-tri-tert-butylpyridine (4) rate constants k(H)/k(D) of 1.14-1.25 are found. The primary kinetic isotope effects observed correlate with the ortho/para ratio of the acylation of toluene. In the presence of 4 a relatively high percentage ( approximately 30%) of ortho product is obtained, whereas under acidic conditions the ratio is only 10%. The correlation between isotope effects and isomer distributions is obviously due to the rate of deprotonation of the corresponding sigma-complex intermediates. Assuming a bent structure for sigma-complexes, the conformation giving deprotonation is preferred in the para sigma-complex in comparison with ortho complex.

Electronic effects of icosahedral carboranes. Friedel-Crafts acylation of 1-phenyl-1,2-, 1,7-, and 1,12-dicarba- closo-dodecaboranes

Friedel-Crafts acylation of the benzene nucleus of 1-phenyl-1,2-, 1,7- and 1,12-dicarba- closo-dodecaboranes (phenylcarboranes) proceeded in the presence of trifluoromethanesulfonic acid. In spite of the strong electron-withdrawing effect of the carborane skeleton, para-acylated products predominated. However, substitution of a methyl group at the 2-position of 1-phenyl-1,2-carborane resulted in a change of isomer distribution.

Synthesis of N.C.A. cis- and trans-4-[18F]fluoro-l-proline, radiotracers for PET-investigation of disordered matrix protein synthesis

A radiosynthesis of n.c.a. (2S,4R)-4-[18F]fluoroproline (trans-configuration) and its disastereomer (2S,4S)-4-[18F]fluoroproline (cis-configuration) has been developed. It allows the routine production of up to 18 GBq of product for clinical purposes in a remote controlled system. The 18F-labelled amino acids were prepared via cryptate mediated n.c.a. nucleophilic 18F-fluorination starting from the corresponding N-Boc-4-(toluene-sulfonyloxy)proline methylester. N-deprotection and ester hydrolysis takes place under acidic conditions in presence of trifluoromethanesulfonic acid. HPLC-purification combined with on-line solid phase extraction yielded the diastereomerically pure 4-[18F]fluoroprolines within 90 min with a radiochemical yield of 36±7% (n=52). Configuration of both isomers was confirmed by comparison with standard compounds which were synthesized via fluorination of the related oxazolidinones with diethylamino sulfurtrifluoride, starting from (2S,4S)- and (2S,4R)-4-hydroxy proline, respectively. Copyright © 1999 John Wiley & Sons, Ltd.

Electrophilic Fluorination of Aromatics with Selectfluor™ and Trifluoromethanesulfonic Acid1

Abstract1‐(chloromethyl)‐4‐fluoro‐1,4‐diazabicyclo[2.2.2]octane bis (tetrafluoroborate) [Selectfluor™ F‐TEDA‐BF4 (TEDA = triethylenediamine)] in the presence of trifluoromethanesulfonic acid has been found to be a very effective reagent system for the direct electrophilic fluorination of a wide variety of aromatic compounds under mild reaction conditions to the corresponding fluoroaromatics in good to excellent yields.

Synthesis of poly(thio-1,4-phenylene) by oxidative coupling reaction of diphenyl disulfide with potassium persulfate in strongly acidic solutions

The synthesis of poly(thio- 1,4-phenylene) (PPS) at room temperature by the reaction of diphenyl disulfide with potassium persulfate (K2S2O8) in non-basic solvents, in the presence of trifluoromethanesulfonic acid, is reported. The reaction in chlorinated solvents, such as dichloromethane and tetrachloroethane, resulted in partial oxidation of sulfide to sulfoxide and sulfone. On the other hand, the polymerization proceeded well in nitrobenzene and the PPS formed was free of branches, crosslinks and thianthrene units. The molecular weight of the polymers formed in different solvents were in the range 2000–8000. The reaction proceeded under identical conditions with bis(2,6-dimethylphenyl) disulfide as well, but the polymer yield was lower.

Catalytic C-amidoalkylations: synthesis of β-amido aldehydes by three-component condensations

Primary amides condense with aliphatic aldehydes (2 equiv.) in the presence of trifluoromethanesulfonic acid to give β-amido aldehydes.

97/02557 Catalytic solubilization of coal and behavior of oxygen containing functional group in the presence of trifluoromethanesulfonic acid

97/02557 Catalytic solubilization of coal and behavior of oxygen containing functional group in the presence of trifluoromethanesulfonic acid

Comparison of α- and β-trifluoromethylsubstituted acrylic acids in their reactions with thiols

α-(Trifluoromethyl)acrylic acid (1) and γ,γ,γ-trifluorocrotonic acid (2) add AcSH (exothermally and at 100 °C, respectively) in the absence of a catalyst to form products of β-thiolation, which can be easily hydrolyzed to the corresponding β-mercaptoalkanoic acids. Thiols also add regiospecifically to acids1 (in the absence of a catalyst) and2 only in the presence of trifluoromethanesulfonic acid as the catalyst) when heated.

Phenylselenenyl sulfate induced cyclization of allylhydrazines. Synthesis of pyrazole derivatives

Abstract Allylhydrazines react with phenylselenenyl sulfate, produced by diphenyl diselenide and ammonium persulfate in the presence of trifluoromethanesulfonic acid, to afford phenylseleno substituted pyrazolidines. Under the reaction conditions employed, these suffer dehydrogenation and oxidative deselenenylation to eventually give pyrazole derivatives.

Regioselective amidation of allylic ?-hydroxyphosphonates with Nitriles: A convenient route to (3-acetylamino-1-alkenyl)-phosphonates

Reaction of dialkyl (1-hydroxy-2-alkenyl)- and (1-hydroxy-2-cycloalkenyl)phosphonates (1) with acetonitrile in the presence of trifluoromethane sulfonic acid (TfOH) affords regiospecifically and with high (E)-stereoselectivity the 1,3-transposed acetamides3 in modest to good yields.

Preparation, Isolation and Characterization of Positional Isomers of Triglucopyranosyl-Cyclomaltoheptaose

Abstract The positional isomers of triglucopyranosyl-cyclomaltoheptaose (β-cyclodextrin, βCD) were chemically synthesized by glucosylations of tris(2, 3-di-O-acetyl)-tetrakis(2, 3, 6-tri-O-acetyl)-βCDs with 2, 3, 4, 6-tetra-O-benzyl-1-O-trichloroacetoimidoyl-α-D-glucopyranose in the presence of trifluoromethanesulfonic acid in dichloromethane, followed by debenzylation and deacetylation. The desired 61, 6X, 6Y-tri-O-(α-D-glucopyranosyl)-βCDs were isolated from each reaction mixture containing their configurational isomers by HPLC and characterized by 13C NMR spectroscopy.

Acid‐Induced Stereoselective Formation of 3,5‐Cycloheptadien‐1‐ones from Ketenes and Dienes

The reaction of ketenes 1a or 1b with diene 2 in the presence of trifluoromethanesulfonic acid providing the cycloheptadienones 5a and 5b constitutes the first example of an acid-induced ketene/diene «cycloaddition». The thermal [2 + 2] cycloadducts, bicyclo[3.2.0]hept-2-en-6-ones 9, are not intermediates in the acid-catalyzed reaction since they rearrange under acidic conditions to the tetralinone derivatives 10. The acid-catalyzed «cycloaddition» was mechanistically investigated and the scope of the reaction explored.

Substitution reactions at silicon under strongly acidic conditions: Ligand metathesis between methyltrichlorosilane and octamethylcyclotetrasiloxane

AbstractA study of the reactions between methyltrichlorosilane (MeSiCl3) and octamethylcyclotetrasiloxane (D4) in the presence of trifluoromethanesulfonic acid (HOTf) showed that nucleophilic substitution in CHCl3 solution at the trifunctional silicon was surprisingly slow in comparison with the rate of equilibration/polymerization of D4. The reaction rate at MeSiCl3 was significantly faster with water present and faster still in THF. In these reactions, there was no evidence for SiOH groups (29Si NMR), even in the presence of excess water. The overriding criterion for relative reactivity toward nucleophilic substitution under strongly acidic conditions is the relative leaving group ability of the groups on silicon. Once MeSiCl3 begins to participate in the redistribution reactions, mono‐ 3 and tri‐ 5, but not di‐substituted 4 systems are formed (MeSiCl3−x(DnSiMe2Z (Z = OTf, Cl))x, x = 1, 3), likely through an intramolecular reaction. The mechanisms of nucleophilic substitution at silicon under these conditions are discussed.