Triflate Derivatives Research Articles

Large-scale synthesis of 6-deoxy-6-sulfonatomethyl glycosides and their application for novel synthesis of a heparinoid pentasaccharide trisulfonic acid of anticoagulant activity

Multigram-scale syntheses of three 6-deoxy-6-sulfonatomethyl α-glucosides were accomplished via reactions of the corresponding primary triflate derivatives with the lithiated ethyl methanesulfonate. Chemoselective glycosylation reactions of different 6-C-sulfonatomethyl glucoside donors were studied. The sulfonic acid-containing building blocks were utilised in a novel [2+3] block synthesis of a trisulfonic acid isoster of the anticoagulant pentasaccharide idraparinux.

Design and Synthesis of Camphor-derived Chiral [1,2,4]Triazolo[4,3-a]tetrahydroquinoline N-Heterocyclic Carbene Precursors by Pd-Catalyzed Coupling Reactions of Aryl Hydrazides with a Pyridyl Triflate Derivative

Which came first? A Pd-catalyzed coupling reaction of N-tert-butyloxycarbonyl (Boc) aryl hydrazines with a camphor-derived pyridyl triflate derivative has been developed by using bulky electron-rich phosphine or N-heterocyclic carbene as the ligand. With this CN coupling reaction as the key step, camphor-derived chiral [1,2,4]triazolo[4,3-a]tetrahydroquinoline N-heterocyclic carbene precursors were synthesized. Tf=trifluoromethanesulfonyl.

Ortho Palladation of the Phenethylamines of Biological Relevance l-Tyrosine Methyl Ester and Homoveratrylamine. Reactivity of the Palladacycles toward CO and Isocyanides. Synthesis of the Natural Alkaloid Corydaldine

Palladacycles derived from l-tyrosine methyl ester, (S)-[Pd2{C,N-C6H3CH2CH(CO2Me)NH2-2,(OH)-4}2(μ-Br)2] (1a-Br), and homoveratrylamine, [Pd2{C,N-C6H2CH2CH2NH2-6,(OMe)2-3,4}2(μ-Br)2] (1b-Br), can be easily prepared in good yield by reacting Pd(OAc)2, the corresponding ammonium triflate, and NaBr. Under the same conditions, the reaction of Pd(OAc)2 with the free amine affords a low yield of the corresponding acetato complex 1a-OAc or 1b-OAc (the latter only detected in solution). In our hands, the previously reported palladation at the C2 position of homoveratrylamine with Pd(OAc)2 is not observed. Instead, a complex mixture is obtained, mainly containing [Pd(OAc)2{NH2CH2CH2C6H3(OMe)2-3,4}2] and minor amounts of 1b-OAc, which reacts with NaBr to afford a new mixture from which [PdBr2{NH2CH2CH2C6H3(OMe)2-3,4}2] can be isolated and characterized. These and other adducts can be isolated from Pd(OAc)2, homoveratrylamine, and various ligands (PPh3 and Br–). 6-Bromohomoveratrylamine reacts with Pd(dba)2 in the presence of tmeda to give the complex [Pd{C,N-C6H2CH2CH2NH2-6,(OMe)2-3,4}(tmeda)]Br. Reactions of complexes 1 with acetylacetonato or neutral (PR3) ligands give products resulting from substitution or bridge-splitting reactions. While 1a-Br reacts with XyNC (1:2 molar ratio) to give (S)-[Pd{C,N-C6H3CH2CH(CO2Me)NH2-2,(OH)-4}Br(CNXy)], 1b-Br gives [Pd{C,N-C(═NXy)-C6H2CH2CH2NH2-6,(OMe)2-3,4}Br(CNXy)]. (S)-7-Hydroxy-3-(methoxycarbonyl)-3,4-dihydroisoquinolin-1(2H)-one and 6,7-dimethoxy-3,4-dihydroisoquinolin-1(2H)-one (corydaldine) have been synthesized through the stoichiometric carbonylation of palladacycles 1a-Br and 1b-Br. The crystal structures of a solvento intermediate in the ortho-metalation reaction of the triflate derivative of l-tyrosine methyl ester and four other complexes have been determined by X-ray diffraction studies.

Synthesis, Isolation and Structural Characterisation of Alkoxytitanium Triflate Complexes

AbstractTreatment of [Ti(OiPr)4] with trimethylsilyl triflate results in the formation of [Ti(OiPr)3(OTf)] (2) in high yield. Subsequent treatment of the triflate derivative 2 with a series of facially coordinating N3‐donor ligands results in the production of a series of charge‐separated metal alkoxide salts of the general formula [{L}Ti(OiPr)3][OTf] {L = tris(pyrazolyl)methane (3a), 1,3,5‐triethyl‐1,3,5‐triazacyclohexane (3b), 1,3,5‐tribenzyl‐1,3,5‐triazacyclohexane (3c), 1,3,5‐tris(p‐fluorobenzyl)‐1,3,5‐triazacyclohexane (3d), and 1,3,5‐tris[(1S)‐1‐phenylethyl]‐1,3,5‐triazacyclohexane (3e)}. The products were characterized by 1H and 13C NMR spectroscopy and in the case of 3a–c by single‐crystal X‐ray diffraction. Reaction of 2 with 1,3,5‐triphenyl‐1,3,5‐triazacyclohexane results in the formation of complex 4 [{L′}2Ti(OiPr)2(OTf)2], which contains two 3,4‐dihydroquinazoline ligands (L′), a result of catalytic activation of the triazacyclohexane ligands by [Ti(OiPr)3(OTf)] towards electrophilic aromatic substitution.

Synthesis and Amination of Oligo(trifluoromethanesulfonyl)dinaphthylmethanes

It was previously shown that the direct amination of 2,2',7,7'-tetrahydroxydinaphthylmethane with primary amines proceeds via the C–C bonds cleavage and the elimination of the methylene unit [1]. At the same time it is known that the catalytic amination of triflate derivatives of phenols and naphthols occurs under mild conditions to give aromatic amines [2–4]. In the present work we reported the first data on the synthesis of 2,2',7,7'-tetratriflato(I) and 2,2'-di(trifluoromethanesulfonyl)dinaphthylmethanes (II) and their subsequent amination.

Synthesis, carbohydrate- and DNA-binding studies of cationic 2,2′:6′,2′′-terpyridineplatinum(ii) complexes containing N- and S-donor boronic acid ligands

A series of platinum(II) complexes of the type [Pt(trpy)L](NO(3))(n) (L = 3- or 4-pyridineboronic acid (3- or 4-pyB, respectively), n = 2; HL = 4-mercaptophenylboronic acid (HmpB), n = 1; trpy = 2,2':6',2''-terpyridine) and [{Pt(trpy)}(2)(μ-pzB)](NO(3))(3) (HpzB = 4-pyrazoleboronic acid) were synthesized and fully characterized by means of multinuclear ((1)H, (13)C, (11)B, and (195)Pt) 1D- and 2D-NMR spectroscopy and elemental analysis. The triflate derivatives [Pt(trpy)(4-pyB)](OTf)(2) and [{Pt(trpy)}(2)(μ-pzB)](OTf)(3) were also prepared, and their molecular structures were confirmed by X-ray crystallography. Variable pH (1)H NMR spectroscopy showed that hydroxylation of the boronic acid group occurs in aqueous solution at pH > 5 and the pK(a) values for the complexes were determined. In buffered aqueous solution (pH 7.4), the complexes bind strongly to simple diols such as catechol and monosaccharides including D-fructose, D-ribose, D-sorbitol and D-mannitol, as determined by isothermal titration calorimetry (ITC). The equilibrium binding constants for these reactions were determined and were found to exceed those of organic boronic acids such as phenylboronic acid by an order of magnitude or greater, an effect that can be directly attributed to the cationic charge of the complexes. 2D-NMR methods (HSQC and HMBC) were used to elucidate the structures of the carbohydrate adducts [Pt(trpy)(3-pyB)]·D-fructose·NO(3) and [Pt(trpy)(4-pyB)]·D-fructose·NO(3) in aqueous solution. DNA-binding experiments with calf-thymus DNA (CT-DNA) indicate an avid DNA-binding interaction by the mononuclear complexes, as determined using thermal melting methods and ITC, but the behaviour of the dinuclear species [{Pt(trpy)}(2)(μ-pzB)](NO(3))(3) is complicated and could not be modeled adequately; higher ionic strength solutions and lower temperatures resulted in a similar DNA binding interaction to the mononuclear complexes. The presence of excess d-fructose did not significantly affect the binding of the platinum(II)-trpy complexes to CT-DNA.

Exploring Chromium(III)−Alkyl Bond Homolysis with CpCr[(ArNCMe)2CH](R) Complexes

A range of paramagnetic Cr(III) monohydrocarbyl complexes CpCr[(ArNCMe)2CH](R) (Ar = ortho-disubstituted aryl; R = primary alkyl, trimethylsilylmethyl, benzyl, phenyl, alkenyl, or alkynyl) were synthesized to investigate how varying the steric and electronic properties of the R group affected their propensity for Cr-R bond homolysis. Most complexes were prepared by salt metathesis of known CpCr[(ArNCMe)2CH](Cl) compounds in Et2O with commercial RMgCl solutions, although more sterically demanding combinations of Ar and R groups necessitated the use of halide-free MgR2 reagents and the Cr(III) tosylate or triflate derivatives. Alternative synthetic routes to Cr(III)-R species using the previously reported Cr(II) compounds CpCr[(ArNCMe)2CH] and sources of R· radicals (e.g., BEt3 and air) were also explored. The UV-vis spectra of the CpCr[(ArNCMe)2CH](R) complexes possessed two strong bands with maximum absorbances in the ranges 395-436 nm and 535-582 nm, with the band in the latter range being particularly characteristic of the Cr(III)-R compounds. The Cr-CH2R bond lengths as determined by single-crystal X-ray diffraction were longer than those in the corresponding Cr-CH3 complexes, typically falling in the range 2.10 to 2.13 Å. The Cr(III) benzyl compounds displayed longer Cr-CH2Ph distances, while the bond lengths for the alkenyl and alkynyl species were substantially shorter. The rate of Cr-R bond homolysis at room temperature was determined by monitoring the reaction of Cr(III) neopentyl, benzyl, and isobutyl complexes with excess PhSSPh using UV-vis spectroscopy. Although the other primary alkyl, phenyl, and alkenyl compounds did not undergo appreciable homolysis under these conditions, they were cleanly converted to CpCr[(ArNCMe)2CH](SPh) by photolysis.

ChemInform Abstract: Palladium‐Catalyzed Coupling Reactions: Carbonylative Heck Reactions to Give Chalcones.

AbstractThe first carbonylative Heck reactions of aryl and alkenyl triflate derivatives with carbon monoxide and aromatic olefins proceed in the presence of palladium catalysts generated in situ.

Chiral copper–bipyridine complexes: Synthesis, characterization and mechanistic studies on asymmetric cyclopropanation

Chiral bipyridine ligands of different steric properties when reacted with CuCl 2 formed orange, yellow or green solids of new copper(II) complexes, [Cu( L)Cl 2] ( L = L2– 6), in good yield. Together with [Cu( L1)Cl 2], these complexes were characterized in solution by UV–Vis spectroscopy and cyclic voltammetry. The complexes give d– d transitions between 860 and 970 nm, and exhibit one quasi-reversible Cu(II)/Cu(I) couple between +0.405 V and +0.516 V versus NHE. Two of the copper(II) complexes, [Cu( L5)Cl 2] and [Cu( L6)Cl 2], and a copper(I) complex of L1, [Cu( L1)Cl], were characterized by X-ray crystallography. The triflate derivatives of both the Cu(I) and Cu(II) complexes are active catalysts towards the cyclopropanation of ethyl diazoacetate with styrene. The asymmetric induction suffers when the size difference between the alkyl and alkoxyl groups was minimized. The mechanism of the cyclopropanation was studied with kinetic and competition experiments. The rate is first order in catalyst and ethyl diazoacetate, inverse order with styrene and is strongly affected by the counterion.

The synthesis, characterization, and alkylation of nacnac chromium triflate derivatives

A Cr(III) triflate coordinated by the bulky β-diketiminate MeL iPr ( MeL iPr = 2,4-pentane N, N′-bis(2,6-diisopropylphenyl)diketiminate) was synthesized from the corresponding bridging iodide complex [ MeL iPrCr(μ-I)] 2 by ligand substitution and subsequent oxidation with silver triflate (AgOTf). MeL iPr Cr III(OTf) 2 exhibits rare trigonal bipyramidal geometry about Cr(III). Attempts to alkylate this triflate synthon with 1,4-dilithiobutane (Li(CH 2) 4Li) led to reduction, while reaction with dimethylzinc (ZnMe 2) led to a mono-alkylated product; only the reaction with methyl lithium (MeLi) was successful in generating a dialkyl.

Palladium‐Catalyzed Coupling Reactions: Carbonylative Heck Reactions To Give Chalcones

The first carbonylative Heck reactions of aryl and alkenyl triflate derivatives with carbon monoxide and aromatic olefins proceed in the presence of palladium catalysts generated in situ.

Palladium‐Catalyzed Synthesis of 4‐Arylcoumarins Using Triarylbismuth Compounds as Atom‐Efficient Multicoupling Organometallic Nucleophiles

AbstractTriarylbismuth compounds have been cross‐coupled as atom‐efficient multicoupling organometallic nucleophiles with 4‐bromo‐ and 4‐(trifluoromethylsulfonyloxy)coumarins under palladium catalysis conditions. These reactions afforded an array of 4‐arylcoumarins in high yields. The general palladium protocol has been demonstrated to be efficient for the coupling of both bromide and triflate derivatives of coumarins with triarylbismuth reagents.

ChemInform Abstract: Novel Cations and Molecules from Phosphaalkynes, 1H-Phosphirenes and from Tetraphosphacubane

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Palladium-catalyzed borylation of l-tyrosine triflate derivative with pinacolborane: practical route to 4-borono-l-phenylalanine (l-BPA) derivatives

Abstract Efficient palladium-catalyzed borylation of protected l -tyrosine triflate with pinacolborane was achieved despite previous reports to the contrary. In addition to the use of an inexpensive boron source, the reaction was carried out in the presence of only 0.5 mol % palladium catalyst. Furthermore, the borylation can be performed using pinacolborane prepared in situ from pinacol and borane–diethylaniline complex. This represents a practical entry to 4-borono- l -phenylalanine ( l -BPA) derivatives.

Preparation of Arylphosphonates by Palladium(0)‐Catalyzed Cross‐Coupling in the Presence of Acetate Additives: Synthetic and Mechanistic Studies

AbstractAn efficient protocol for the synthesis of arylphosphonate diesters via a palladium‐catalyzed cross‐coupling of H‐phosphonate diesters with aryl electrophiles, promoted by acetate ions, was developed. A significant shortening of the cross‐coupling time in the presence of the added acetate ions was achieved for bidentate and monodentate supporting ligands, and for different aryl electrophiles (iodo, bromo and triflate derivatives). The reaction conditions were optimized in terms of amount of the catalyst, supporting ligands, and source of the acetate ion used. Various arylphosphonates, including those of potential biological significance, were synthesized using this newly developed protocol. Some mechanistic aspects of the investigated reactions are also discussed.

Amphiphilic Long-chain Citric Acid Ethers

The etherification of the hydroxyl group of citric acid with saturated and unsaturated long-chain alkyl groups is described. This is a new approach to polydentate acids which may serve as ligands for metal or metal oxide nanoparticles. For this purpose we developed a synthetic route to long-chain ω-unsaturated alcohols and their triflate derivatives.

Coordination Chemistry of Tetrakis(diphenylphosphinomethyl)methane: Binuclear, Tetranuclear and Polymeric Complexes

The ligand tetrakis(diphenylphosphinomethyl)methane, tpmm, binds in a η2, η2- bridging mode to square planar platinum(II) or palladium(II) centers to give complexes such as [Pt2Me4(μ-tpmm)] or [Pd2Cl4(μ-tpmm)]. These complexes yielded triflate derivatives [Pt2Me2(OTf)2(μ-tpmm)] or [Pd2(OTf)4(μ-tpmm)], and displacement of triflate by a bipyridine ligand then gave the cationic polymers [{Pt2Me2(μ-LL)(μ-tpmm)}n]2n+ or the cationic network materials [{Pd2(μ-LL)2(μ-tpmm)}n]4n+, LL=4,4’-bipyridine or 1,3-C6H4(CONH-4-C5H4N)2. Ligand tpmm reacts with copper(I) iodide to give [Cu4I4(μ-tpmm)2] or with silver(I) triflate to give [Ag2(OTf)2(μ-tpmm)], which then reacts with LL=1,3-C6H4(CONH-4-C5H4N)2 to give the polymeric complex [{Ag2(μ-LL)(μ-tpmm)}n]2n+. The structure determination of [Cu4I4(μ-tpmm)2] shows that it contains two isomeric forms with the tpmm ligands in either the η2, η2- or η3, η1- bridging mode.

Synthesis and characterization of fluorinated phosphonium ionic liquids

A wide variety of phosphonium ionic liquids containing fluorous ponytails Rfn (Rfn = –(CF2)n–1CF3; n = 4, 6, 10) are synthesized by the reaction of Rfn-(CH2)2-I with trialkylphosphines (R3P; R = Me, nBu, nOct). The efficacy of multiple metathetical routes to anion exchange have been investigated, thus the corresponding BF4–, PF6–, tosylate (OTs–) and triflate (OTf–) derivatives have also been prepared. All compounds have been comprehensively characterized by multinuclear NMR spectroscopy, ESI-MS, DSC, and TGA/SDTA, and in the case of [Me3PCH2CH2Rf4][I] by single crystal X-ray diffraction. These materials range from high melting solids (e.g., [Me3P(CH2)2Rf4][I] Tm = 195 °C) to very low melting liquids (e.g., [nOct3P(CH2)2Rf4][OTf] Tg = –64 °C), and they all have high thermal decomposition points (295 to 394 °C). Incorporation of the more weakly coordinating BF4– and PF6– yielded a significant increase in the melting point of the materials, in contrast to OTf– and OTs– derivatives, which all exhibited significantly depressed melting points.Key words: phosphonium ionic liquids, alternative solvents, fluorine, phosphorus, fluorous ponytails.

A Convenient, NMR-Based Method for the Analysis of Diastereomeric Mixtures of Pseudoephedrine Amides

Amides of pseudoephedrine and ephedrine are shown to undergo highly stereospecific, invertive cyclization to form 4,5-dihydro-3,4-dimethyl-5-phenyl-1,3-oxazolium triflate derivatives in the presence of triflic anhydride-pyridine. 1H NMR spectra of the unpurified reaction products are remarkably clean, with sharp, well-defined peaks, and allow for rapid assessment of the diastereomeric purities of the starting amides. [reaction: see text].

Synthesis and MMA polymerization of chiral ansa-zirconocene ester enolate complexes with C2- and Cs-ligation

A series of chiral ansa-zirconocene ester enolate complexes incorporating C 2- or C s-symmetric ligands, including neutral rac-(EBI)ZrCl[OC(O i Pr) CMe 2] ( 1), rac-(EBI)Zr(OTf)[OC(O i Pr) CMe 2] ( 2), rac-(EBI)Zr(OTf)[OC(OMe) C(Me)CH 2C(Me 2)C(O i Pr) O] ( 3), [Me 2C(Cp)(Flu)]ZrMe[OC(O i Pr) CMe 2] ( 4), and cationic [Me 2C(Cp)(Flu)]Zr +(THF)[OC(O i Pr) CMe 2][MeB(C 6F 5) 3] − ( 5), have been synthesized. Within the neutral C 2-ligated zirconocene ester enolate series, the chloride derivative 1 is inactive toward any methyl methacrylate (MMA) additions, the methyl derivative rac-(EBI)ZrMe[OC(O i Pr) CMe 2] adds cleanly only 1 equiv. of MMA, and the triflate derivative 2 can add either 1 equiv. of MMA to form the single-MMA-addition product 3 or multiple equivalents of MMA to form P(MMA). Unlike the C s-ligated methyl cation [Me 2C(Cp)(Flu)ZrMe] +, which is inactive for MMA polymerization under various conditions, the C s-ligated ester enolate cation 5 is moderately active for polymerization of MMA and N, N-dimethylacrylamide at ambient temperature; the resulting P(MMA) has a high molecular weight of M n = 388 000 Da but a low syndiotacticity of [ rr] = 64%, and the polymerization conforms to a chain-end control mechanism.