Syntheses of aliphatic polyesters catalyzed by lanthanide triflates

Polycondensations of 1,6‐hexane diol and sebacic acid were conducted in bulk with addition of a lanthanide triflate as acidic catalyst. With exception of promethium triflate all lanthanide triflates were studied. A particularly low molecular weight was obtained with neodym triflate and the best results with samarium triflate. With Sm(OTf)₃ weight average (M_w) values up to 65 kDa (uncorrected SEC data) were achieved after optimization of the reaction conditions. Comparison of these results with those obtained from bismuth, magnesium, and zinc triflates, on the one hand, and comparison with the acidities of all catalysts, on the other, indicates that the esterification mechanism involves complexation of monomer by metal ions. Preparation of multiblock copoly(ether ester)s failed due to insufficient incorporation of poly(tetrahydrofuran) diols. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 170–177, 2009     

Synthesis of arylated xanthones by site-selective Suzuki–Miyaura reactions of the bis(triflate) of 1,3-dihydroxyxanthone

Arylated xanthones were prepared by site-selective Suzuki–Miyaura reactions of the bis(triflate) of 1,3-dihydroxyxanthone. The first attack occurs at the sterically less encumbered position 3. The site-selectivity is in contrast to the bis(triflate) of 1,3-dihydroxyanthraquinone.     

Iron-catalysed green synthesis of carboxylic esters by the intermolecular addition of carboxylic acids to alkenes

Iron triflate, in situ-formed from FeCl3 and triflic acid, or FeCl3 and silver triflate efficiently catalyse the intermolecular addition of carboxylic acids to various alkenes to yield carboxylic esters; the reaction is applicable to the synthesis of unstable esters, such as acrylates.     

Attachment of the anthramycin acrylamide side chain by the palladium catalyzed coupling reaction of a vinyl triflate

Conversion of the 2-keto group in the pyrrolo ring of pyrrolo(1,4)benzodiazepines to the vinyl triflate takes place regiospecifically to yield the enamine. The triflate undergoes palladium catalyzed coupling reactions to attach the acrylamide side chain.     

A highly efficient d-fructofuranosylation catalyzed by scandium(III) triflate

This Letter describes a highly efficient d-fructofuranosylation catalyzed by scandium(III) triflate. The benzylated and benzoylated d-fructofuranosyl acetate derivatives worked as good reactive donors in the presence of only 5 mol % scandium(III) triflate at 0 °C in toluene to afford the d-fructofuranosides in excellent yields. The fructofuranosylation also produced several non-reducing disaccharides of sucrose mimics using several aldopyranose derivatives as the acceptors.     

A convenient synthesis of triflate anion ionic liquids and their properties

A solvent- and halogen-free synthesis of high purity triflate ionic liquids via direct alkylation of organic bases (amines, phosphines or heterocyclic compounds) with methyl and ethyl trifluoromethanesulfonate (methyl and ethyl triflate) has been developed. Cheap and non-toxic dimethyl and diethyl carbonate serve as source for the methyl and ethyl groups in the preparation of methyl and ethyl triflate by this invented process. The properties of ionic liquids containing the triflate anion are determined and discussed.     

Cyclization of olefinic alcohol by benzeneselenenyl triflate

Cyclization of 4-, 5-, and 6-hydroxyalkenes with benzeneselenenyl triflate afforded correspondingtetrahydrofurans and -pyrans.     

The Friedel-Crafts acylation of aromatic compounds with carboxylic acids by the combined use of perfluoroalkanoic anhydride and bismuth or scandium triflate

Aromatic ketones were synthesized by solventless Friedel-Crafts acylation of anisole, mesitylene, xylenes, and toluene with acetic acid and benzoic acid in the presence of trifluoroacetic anhydride by use of bismuth or scandium triflate at 30 °C. Toluene, benzene, and even deactivated substrate such as chlorobenzene were benzoylated by the combined use of heptafluorobutyric anhydride and bismuth triflate at 75-100 °C. The catalyst could be easily recovered and reused repeatedly for the reaction.     

Novel and efficient synthesis of 4-dimethylamino-2-glycosylaminoquinazolines by cyclodesulfurization of glycosyl thioureas with dimethylcyanamide

4-dimethylamino-2-glycosylaminoquinazoline derivatives were synthesized by cyclodesulfurization of N-aryl-N'-glycosyl thioureas with dimethylcyanamide in the presence of silver triflate in good yields.     

Vibrational spectroscopic and ab initio molecular orbital studies of the normal and 13C-labelled trifluoromethanesulfonate anion

Infrared and Raman spectra of both normal and ¹³C-labelled tetrabutylammonium trifluoromethanesulfonate (triflate) [Bu₄N·CF₃SO₃] and mercury triflate Hg(CF₃SO₃)₂ were recorded at room temperature. The observed isotopic frequency shifts and bandwidths in the vibrational spectra of the triflate anion were taken into account in the assignments of the vibrational modes of the triflate anion. These assignments were supported by ab initio Hartree—Fock self-consistent field (HF-SCF) calculations of vibrational frequencies and normal modes for the triflate anion.     

Influence of the alkyl group of triflate esters on their initiation ability for the cationic ring-opening polymerization of tetrahydrofuran

Esters of trifluoromethane sulfonic acid have been synthesized by reaction of different alcohols with triflic anhydride and used in situ as initiators for the polymerization of tetrahydrofuran. Kinetic studies of the polymerization showed that allyl triflate has the highest reactivity and that an increase of the alkyl chain length of the initiator leads to a significant decrease of the initiation rate. “Non-linear” triflate ester such as isobutyl triflate leads to incomplete initiation. It was impossible to synthesize quantitatively the triflate from tert-butyl alcohol due to spontaneous elimination leading to isobutylene.     

Molecular dynamics simulations of triflic acid and triflate ion/water mixtures: a proton conducting electrolytic component in fuel cells

Triflic acid is a functional group of perflourosulfonated polymer electrolyte membranes where the sulfonate group is responsible for proton conduction. However, even at extremely low hydration, triflic acid exists as a triflate ion. In this work, we have developed a force-field for triflic acid and triflate ion by deriving force-field parameters using ab initio calculations and incorporated these parameters with the Optimized Potentials for Liquid Simulations - All Atom (OPLS-AA) force-field. We have employed classical molecular dynamics (MD) simulations with the developed force field to characterize structural and dynamical properties of triflic acid (270-450 K) and triflate ion/water mixtures (300 K). The radial distribution functions (RDFs) show the hydrophobic nature of CF(3) group and presence of strong hydrogen bonding in triflic acid and temperature has an insignificant effect. Results from our MD simulations show that the diffusion of triflic acid increases with temperature. The RDFs from triflate ion/water mixtures shows that increasing hydration causes water molecules to orient around the SO(3)(-) group of triflate ions, solvate the hydronium ions, and other water molecules. The diffusion of triflate ions, hydronium ion, and water molecules shows an increase with hydration. At λ = 1, the diffusion of triflate ion is 30 times lower than the diffusion of triflic acid due to the formation of stable triflate ion-hydronium ion complex. With increasing hydration, water molecules break the stability of triflate ion-hydronium ion complex leading to enhanced diffusion. The RDFs and diffusion coefficients of triflate ions, hydronium ions and water molecules resemble qualitatively the previous findings using per-fluorosulfonated membranes.     

A new strategy for the synthesis of benzoxanthenes catalyzed by proline triflate in water

Catalyzed by proline triflate, benzoxanthenes were obtained in good yields from the condensation of naphthols, aldehydes, and 1,3-dicarbonyl compounds in water. A possible mechanism of this reaction is proposed.     

A Two‐in‐one Pincer Ligand and its Diiron(II) Complex Showing Spin State Switching in Solution through Reversible Ligand Exchange

A novel pyrazolate‐bridged ligand providing two {PNN} pincer‐type compartments has been synthesized. Its diiron(II) complex LFe₂(OTf)₃(CH₃CN) ( 1 ; Tf=triflate) features, in solid state, two bridging triflate ligands, with a terminal triflate and a MeCN ligand completing the octahedral coordination spheres of the two high‐spin metal ions. In MeCN solution, 1 is shown to undergo a sequential, reversible, and complete spin transition to the low‐spin state upon cooling. Detailed UV/Vis and ¹⁹F NMR spectroscopic studies as well as magnetic measurements have unraveled that spin state switching correlates with a rapid multistep triflate/MeCN ligand exchange equilibrium. The spin transition temperature can be continuously tuned by varying the triflate concentration in solution.     

β‐Selective Glycosylation by Using O‐Aryl‐Protected Glycosyl Donors

New glycosyl donors have been developed that contained several para‐substituted O‐aryl protecting groups and their stereoselectivity for the glycosylation reaction was evaluated. A highly β‐selective glycosylation reaction was achieved by using thioglycosides that were protected by 4‐nitrophenyl (NP) groups, which were introduced by using the corresponding diaryliodonium triflate. Analysis of the stereoselectivities of several glycosyl donors indicated that the β‐glycosides were obtained through an S_N2‐type displacement from the corresponding α‐glycosyl triflate. The NP group could be removed by reduction of the nitro group and acylation, followed by oxidation with ceric ammonium nitrate (CAN).     

Chemoselective Synthesis of Asymmetrical Carbonate from Alcohol and Dimethyl Carbonate Catalyzed by Ytterbium(III) Triflate

Catalyzed by ytterbium(III) triflate, asymmetrical carbonate can be chemoselectively synthesized from alcohols and dimethyl carbonate (DMC) in moderate to good yield under the mild conditions.     

Highly stereoselective c-allylation of glycopyranosides with allylsilanes catalyzed by silyl triflate or iodosilane

Methyl α-D-glucopyranoside, methyl α-D-mannopyranoside and, in particular, the corresponding α-D-glycopyranosyl chlorides readily undergo allylation with allylsilanes catalyzed by trimethylsilyl triflate or iodotrimethylsilane in a highly stereoselective mode.     

Some new acridinium trifluoromethanesulfonates as spectrophotometric derivatization reagents for aromatic and aliphatic primary amines

Some new 9-substituted 10-methylacridinium trifluoromethanesuifonate (triflate) salts have been synthesized and shown to react in methanol with the model aromatic and aliphatic amines, aniline and n-butylamine, to form derivatives which absorb strongly at 445 and 439 nm, respectively. The color development is affected by heat and heating time and by the quantity of acridinium triflate used. A 10-50-fold molar excess of the triflate should be used and the solution heated at 60 degrees for 30 min. The linearity and reproducibility of the assay are improved by the presence of pyridine (for aniline) and triethylamine (for n-butylamine) in the reaction mixture. Beer's law is obeyed over the range 0-1860 ng/ml for aniline and 0-1440 ng/ml for n-butylamine, with each of the new reagents. The relative error and the precision of determination depends on the acridinium triflate used.     

Imidazolium ionic liquids as solvents for cerium(IV)-mediated oxidation reactions

Use of imidazolium ionic liquids as solvents for organic transformations with tetravalent cerium salts as oxidizing agents was evaluated. Good solubility was found for ammonium hexanitratocerate(IV) (ceric ammonium nitrate, CAN) and cerium(IV) triflate in 1-alkyl-3-methylimidazolium triflate ionic liquids. Oxidation of benzyl alcohol to benzaldehyde in 1-ethyl-3-methylimidazolium triflate was studied by in-situ FTIR spectroscopy and 13C NMR spectroscopy on carbon-13-labeled benzyl alcohol. Careful control of the reaction conditions is necessary because ammonium hexanitratocerate(IV) dissolved in an ionic liquid can transform benzyl alcohol not only into benzaldehyde but also into benzyl nitrate or benzoic acid. The selectivity of the reaction of cerium(IV) triflate with benzyl alcohol in dry ionic liquids depends on the degree of hydration of cerium(IV) triflate: anhydrous cerium(IV) triflate transforms benzyl alcohol into dibenzyl ether, whereas hydrated cerium(IV) triflate affords benzaldehyde as the main reaction product. Reactions of ammonium hexanitratocerate(IV) with organic substrates other than benzyl alcohol have been explored. 1,4-Hydroquinone is quantitatively transformed into 1,4-quinone. Anisole and naphthalene are nitrated. For the cerium-mediated oxidation reactions in ionic liquids, high reaction temperatures are an advantage because under these conditions smaller amounts of byproducts are formed.     

Cyclic vinylogous triflate hemiacetals as new surrogates for alkynyl aldehydes

Cyclic vinylogous triflate hemiacetals can serve as ‘synthetic equivalents’ for alkynyl aldehydes: treatment of a vinylogous triflate hemiacetal with excess amounts of Grignard reagents produces acyclic alkynyl alcohols in good to high yields. This transformation likely involves the Grob-type C-C bond cleaving fragmentation to form the alkynyl aldehyde in situ. Subsequent nucleophilic attack of the Grignard reagent furnishes secondary alkynols. Vinylogous triflate hemiacetals are easily prepared by DIBALH reduction of vinylogous acyl triflates, which are derived from cyclic 1,3-diketones.