Sulfonium Triflate Research Articles

Theoretical Study, Synthesis, and Reactivity of Five‐Membered‐Ring Acyl Sulfonium Cations

AbstractThe feasibility of the cyclization of γ‐alkylthiobutyric acid derivatives to form previously unknown five‐membered‐ring acyl sulfonium cations was studied. Experimental results were in good agreement with our DFT calculations that predicted such cyclizations to be easy if starting with acyl iodides and mixed anhydrides of triflic acid. Particularly efficient were the reactions of γ‐alkylthiobutyryl fluorides with trimethylsilyl triflate in CDCl3 solution, which led to cyclic acyl sulfonium triflates. In some cases, the observed acyl sulfonium salts were stable enough to be characterized by NMR spectroscopy. They were found to be both alkyl‐transfer reagents and acylating agents. They react with amines to form amides. These findings lend some weight to our hypothesis that the acyl sulfonium derived from methionine may have played a major role in the prebiotic synthesis of the first peptides on the primitive Earth.

An Efficient Synthesis of Azetidines with (2-Bromoethyl)sulfonium Triflate

Easily accessible arylglycine derivatives were cyclized to azetidines by using commercially available (2-bromoethyl)sulfonium triflate in a simple and mild procedure. The high-yielding reaction has a relatively broad scope and was extended to the synthesis of an oxetane.

Photoinitator surface segregation induced instabilities from polymerization of a liquid coating on a rigid substrate

Periodic wrinkled surfaces have generated significant interest over the past decade as these structures can be easily fabricated over large areas with minimal fabrication cost, but these structures have generally been limited to thin films on soft elastomeric substrates, which limits their general applicability and utility. Here we present a simple methodology to generate wrinkled surfaces on rigid substrates by surface segregation of a photocatalyst. Upon ultraviolet light (UV) induced photopolymerization, increased catalyst concentration yields a cross-linked layer at the free surface that is supported on top of a more liquid-like bulk film due to differences in polymerization rate. Further polymerization of the underlayer provides the requisite mechanical stress (contraction due to polymerization) to create a wrinkled pattern. A system based upon the renewable monomer, furfuryl alcohol, that is cross-linked with a photoacid generator, triphenyl sulfonium triflate, is utilized to illustrate this concept. Moreover, the polymerized furfuryl alcohol can be transformed into amorphous carbon by heating at elevated temperatures in an inert environment. The role of photoacid generator concentration and substrate temperature on the wrinkle formation and morphology is presented. Finally, exposure through a simple mask can generate hierarchical structures with the wrinkled structure conforming to the geometric constraints of the photopatterned area, including curvilinear structures. This photocatalyzed surface segregation-based methodology provides a promising route to the facile fabrication of microstructured surfaces based upon the wrinkling instability.

ChemInform Abstract: A Facile Synthesis of 2-Deoxy-2,3-didehydroneuraminic Acid Derivatives.

The 2-thio- or 2-selenoglycosides of N-acetylneuraminic acid methyl ester were transformed by successive treatment with dimethyl(methylthio)sulfonium triflate (DMTST) and 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) to give the corresponding methyl 2-deoxy-2,3-didehydroneuraminates in excellent yields. Their acids and their analogues are sialidase inhibitors of pharmaceutical interest.

Efficient Synthesis of Three Types of Sialyl 6-O-Sulfo Lewis X: Probes for the Comprehensive Search for the Interaction between Carbohydrates and Other Biomoleclues

Synthesis of three kinds of 6-O-sulfated sLe x glyco probes with their relevance to ligand processing pathway of L-selectin has been described. The glycosylation of the suitably protected hexasaccharide acceptor 6 with the sialyl-a-(2→3)-D-galactopyranosyl SMe donors (3 and 4) using dimethyl(methylthio)sulfonium triflate (DMTST), afforded the protected tetrasaccharides 7 and 8, respectively. Removal of all the benzyl protecting groups and the subsequent acetylation afforded the sLe x derivatives (9 and 10), which were converted to the target compounds (15 and 16) by the selective removal of 4-methoxyphenyl group, followed by 6-O-sulfation of the GlcNAc residue, and removal of all the protective groups under basic conditions. Finally 16 was lactamized with HBTU and HOBT, to give the desired target compound 17.

Sulfur Ylide Mediated Three-Component Aziridination and Epoxidation Reactions Using Vinyl Sulfonium Salts

Coupling of diphenylvinyl sulfonium triflate with nucleophiles and either aldehydes or imines gives epoxides and aziridines, respectively, in a three-component reaction. cis-Aziridines could be formed in good diastereomeric ratio, and the selectivity was correlated to the reactivity of the imine. This represents the first study of cis/trans selectivity in the reactions of imines with non­stabilized sulfur ylides.

Atomic force microscope anodization lithography using a triarylsulfonium salt photoinitiator

Photoacid generators (PAGs) have been widely used as a key component in the development of chemically amplified photoresist. In this study, a PAG with good thermal stability and an electron-withdrawing group was applied to AFM anodization lithography. Specifically, triarylsulfonium salts (TAS) such as a diphenyl(4-tert-butoxycarbomethoxyphenyl)-sulfonium triflate (DTCPS-Tf) and triphenyl-sulfonium triflate (TPS-Tf) were used successfully to fabricate anodized nanostructures by AFM anodization lithography. In addition, the effect of electron-withdrawing materials and optimized lithographic conditions were studied through a systematic alteration of lithographic factors such as applied voltage, lithographic speed, and humidity.

Solid‐Phase Synthesis of Sialyl Tn Antigen

Solid‐phase synthesis of sialyl Tn [α‐Neu5Ac‐(2→6)‐α‐GalNAc‐(1→O)‐Ser] antigen with Kenner's acylsulfonamide linker is described. The acylsulfonamide bond was found to be stable under glycosylation reactions using dimethyl(methylthio)sulfonium triflate (DMTST) as a promoter and basic conditions used for the removal of protecting groups. The solid‐phase reaction was monitored by the inverse gated decoupling 13C NMR technique, which enabled quantitative analysis of the reaction progress. At the end of the synthesis, the sulfamyl group of the linker was activated by treatment with (trimethylsilyl)diazomethane to provide a N‐methyl‐N‐acylsulfonamide. The acyl group was displaced with hydroxide to give the corresponding precursors of sialyl Tn antigen and its anomeric isomers, which were deprotected to afford the target molecules.

Sulfonium Triflate Mediated Glycosidations of Aryl 2‐Azido‐2‐deoxy‐1‐thio‐D‐mannosides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Sulfonium Triflate Mediated Glycosidations of Aryl 2‐Azido‐2‐deoxy‐1‐thio‐D‐mannosides

AbstractThe effectiveness in terms of yield and stereoselectivity of (phenylsulfinyl)piperidine (BSP) 1b/ trifluoromethanesulfonic anhydride (Tf2O) and diphenyl sulfoxide (DPS) 1c/Tf2O‐mediated glycosidations of 2‐azido‐3‐O‐benzyl‐4,6‐O‐benzylidene‐2‐deoxy‐D‐thiomannosides 2a/b is described. Application of the BSP/Tf2O activator led to productive condensations using p‐methoxyphenyl 2‐azido‐3‐O‐benzyl‐4,6‐O‐benzylidene‐2‐deoxy‐D‐thiomannoside (2b) as a donor, while the more powerful DPS/Tf2O combination gave similar results using both p‐methoxyphenyl and phenyl 2‐azido‐3‐O‐benzyl‐4,6‐O‐benzylidene‐2‐deoxy‐D‐thiomannosides 2a/b. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

A Modular Strategy Toward the Synthesis of Heparin-like Oligosaccharides Using Monomeric Building Blocks in a Sequential Glycosylation Strategy

A novel flexible assembly strategy is described for the modular synthesis of heparin and heparan sulfates. The reported strategy uses monomeric building blocks to construct the oligosaccharide chain to attain a maximum degree of flexibility. In the assembly, 1-hydroxyl glucosazido- and 1-thio uronic acid donors are combined in a sequential glycosylation protocol using sulfonium triflate activator systems. The key 1-thio uronic acids were obtained in an efficient manner from diacetone glucose employing a chemo- and regioselective oxidation of partially protected glucose and idose thioglycosides.

A Convenient Method for the Synthesis of α‐Imidostyrenes from Styrenes and Imides via Diphenylstyrylsulfonium Salts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Convenient Method for the Synthesis of α-Imidostyrenes from Styrenes and Imides via Diphenylstyrylsulfonium Salts

Abstract Styrenes having a hydrogen atom at the α-position reacted with diphenyl(trifluoromethanesulfonyloxy)sulfonium triflate (1) to form diphenylstyrylsulfonium triflates 2 that were in turn converted into the corresponding α-imidostyrenes on treatment with sodium or potassium salts of cyclic imides.

A Convenient Method for the Synthesis of β,γ‐Unsaturated Amines from Alkenes via α,β‐Unsaturated Diphenylsulfonium Salts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Convenient Method for the Synthesis of 2‐Arylaziridines from Styrene Derivatives via 2‐Arylethenyl(diphenyl)sulfonium Salts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Convenient Method for the Synthesis of β,γ-Unsaturated Amines from Alkenes via α,β-Unsaturated Diphenylsulfonium Salts

Abstract 1,1-Disubstituted and trisubstituted alkenes were converted into the corresponding β,γ-unsaturated amines 4 via three steps: the initial formation of α,β-unsaturated diphenylsulfonium triflates 2 from alkenes and diphenyl(trifluoromethanesulfonyloxy)sulfonium trifluoromethanesulfonate (1), followed by double bond migration of 2 to β,γ-unsaturated sulfonium triflates 3 with primary or secondary amines, and successive nucleophilic substitution of 3 with these amines.

A Convenient Method for the Synthesis of 2-Arylaziridines from Styrene Derivatives via 2-Arylethenyl(diphenyl)sulfonium Salts

Abstract Styrene derivatives reacted with diphenyl(trifluoromethanesulfonyloxy)sulfonium trifluoromethanesulfonate (1) at low temperature to afford 2-arylethenyl(diphenyl)sulfonium triflates (2). Treatment of 2 with primary amines gave the corresponding 2-arylaziridines in high yields. One-pot synthesis of various aziridines was also successfully carried out without isolation of the intermediate 2.

Exploratory Study of the Reaction of Bis(2‐methoxyethyl)aminosulfur Trifluoride (Deoxofluor Reagent) with Diaryl Sulfoxides: Novel Routes to Ar2SF2 and Ar2SF(OTf) via Sulfoxide Activation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Exploratory study of the reaction of bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor™ reagent) with diaryl sulfoxides: novel routes to Ar 2SF 2 and Ar 2SF(OTf) via sulfoxide activation

Neither bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor™ reagent) nor HF/pyridine alone can fluorinate diaryl sulfoxides. S-fluorination can be effected by activating the sulfoxide via protonation with HF/pyridine (70:30) to form sulfoxonium ions in equilibrium which are then S-fluorinated in situ with Deoxofluor™ to give Ar 2SF 2 compounds. Conversions depend strongly on steric factors and the reactions require the use of excess Deoxofluor™ and HF/pyridine. NMR data for the resulting diarylsulfur difluorides are gathered and discussed. Sulfoxide activation via diaryl (trifloxy) sulfonium triflate generated in situ from Ar 2SO with triflic anhydride at low temperature represents another strategy for S-fluorination with Deoxofluor™ to generate Ar 2S(OTf)F.

Oxidation of Primary Alkyl Triflates to the Corresponding Aldehydes via Alkoxy(N-tert-butylamino)(methyl)sulfonium Triflates

Abstract Various alkoxy(N-tert-butylamino)(methyl)sulfonium triflates are prepared by selective O-alkylation of N-tert-butylmethanesulfinamide (4c) with primary alkyl trifluoromethanesulfonates (triflates). Successive treatment of thus formed alkoxyaminosulfonium salts with DBU smoothly affords the corresponding aldehydes in good yields. The sequential combination of the two reactions provides a new method for oxidation of primary alkyl triflates to aldehydes, and the present study suggests the existence of alkoxysulfilimines as intermediates of the previously-reported direct oxidation of alcohols by using N-tert-butylphenylsulfinimidoyl chloride (1a) and DBU.