Trimethylsulfonium Research Articles

Solvent effects on the intramolecular conversion of trimethylsulfonium chloride to dimethyl sulfide and methyl chloride.

The formation of CH3Cl from (CH3)3SCl in various solvents has been studied based on M05/6-311+G(2d,p) DFT calculations to quantify the influence of the solvent on the stability of sulfonium cations. Four different pathways (one SN1, one backside and two frontside attacks for SN2) as well as the formation of different ion pairs (tripod, seesaw, and linear) are discussed to investigate the origin of the kinetic solvent effect (KSE) and the contribution of ion pairs to the overall reaction. Ion pairs are formed only in solvents with a permittivity ε lower than 28, but the reaction proceeds via a standard SN2 mechanism with a backside attack in all solvents. The formation of ion pairs does not change the order of the rate law, but it strongly influences the KSE, which can distinguish between reactions starting from free ions and those starting from ion pairs, in contrast to standard kinetic analysis.

Simultaneous determination of nine pharmaceuticals personal care products in waters by solid phase extraction-gas chromatography-mass spectrometry

An analytical method has been developed and validated for the simultaneous determination of nine pharmaceuticals and personal care products (PPCPs) in water samples, including salicylic acid, naproxen, ibuprofen, paracetamol, clofibric acid, triclosan, diclofenac, ketoprofen, bisphenol A. The qualification and quantification of the target compounds were performed by gas chromatography-mass spectrometry in selected ion monitoring mode (GC-MS-SIM). The water samples were concentrated and purified through Oasis HLB cartridges after the pH value of the water was adjusted to 3, then derivatized with trimethyl sulfonium hydroxide (TMSH) at room temperature, and determined by GC-MS-SIM using 2,4,5-fenoprop as internal standard. The conditions for sample pretreatment (e. g. solid phase extraction and derivatization) were studied. Under the optimized conditions, the recoveries were ranged from 50.7% to 115.4% with the relative standard deviations lower than 10%. The limits of detection were in the range of 0.03-0.30 microg/L and the limits of quantification were in the range of 0.15-1.50 microg/L. The method has been successfully applied to monitor the occurrence of the PPCPs residues in agricultural irrigation water in Dongguan, Guangdong Province. The four compounds were detected at maximum mass concentration range of 0.176-0.998 microg/L. It proved that this analytical method is sensitive, reliable and acceptable.

A constrained reduced-dimensionality search algorithm to follow chemical reactions on potential energy surfaces

A constrained reduced-dimensionality algorithm can be used to efficiently locate transition states and products in reactions involving conformational changes. The search path (SP) is constructed stepwise from linear combinations of a small set of manually chosen internal coordinates, namely the predictors. The majority of the internal coordinates, the correctors, are optimized at every step of the SP to minimize the total energy of the system so that the path becomes a minimum energy path connecting products and transition states with the reactants. Problems arise when the set of predictors needs to include weak coordinates, for example, dihedral angles, as well as strong ones such as bond distances. Two principal constraining methods for the weak coordinates are proposed to mend this situation: static and dynamic constraints. Dynamic constraints are automatically activated and revoked depending on the state of the weak coordinates among the predictors, while static ones require preset control factors and act permanently. All these methods enable the successful application (4 reactions are presented involving cyclohexane, alanine dipeptide, trimethylsulfonium chloride, and azafulvene) of the reduced dimensionality method to reactions where the reaction path covers large conformational changes in addition to the formation/breaking of chemical bonds. Dynamic constraints are found to be the most efficient method as they require neither additional information about the geometry of the transition state nor fine tuning of control parameters.

Physiological basis of effective controlling Torpedo grass (Panicum repens L.)

Torpedo grass (Panicum repens L.) is a C4 plant species, present on different soil types. The rhizome system and tubers of grass well developed, although flowering but not yet recorded the presence of seeds and seedlings (Yêu cầu tác giả viết lại toàn bộ câu này, không thể sửa được. Lưu ý câu phải có động từ chính). Tuber has high drought tolerance. Regenerative ability of the grass decreases with water content of the tuber. Tuber inability to regenerate shoots when it has water less than 30% of water at first. Repeatedly cut grass will take the tuber reserve depletion, not sufficient to provide for the regeneration bud sprouts. Coordinate disposal of mowing and using systemic herbicides will lead to better results. 6-8 weeks after cutting, the grass grow well with multiple shoots, spraying glyphosate 480 SL or glyphosate trimethyl sulphonium (GTS) at doses of 6-8 l / ha, mixed with urea at concentrations from 1% to 1.5%. This way helps prevent the emergence of shoots from rhizomes and tubers.

Synthesis and properties of regio-regular poly(2-furyloxirane) using tri-isobutyl aluminium as catalyst

2-Furyloxirane(FO) with purity of over 99% was prepared in 80% yield by epoxidation of furfural with trimethylsulfonium chloride and potassium hydroxide in acetonitrile/water solution. Polymerization of FO was realized using tri-isobutyl aluminum (Al(i-Bu)3) as catalyst, when Al(i-Bu)3 concentration was 0.009 mol/L, poly(2-furyloxirane)(PFO) with Mn of 3.4 kg/mol and a polydispersity index of 1.5 was obtained in yield of 88% after polymerization at 25 °C for 48 h. The corresponding PFO showed glass transition temperature (Tg) of Ca. 1 °C and 5 wt% thermal decomposition temperature(Td) of 260 °C. The obtained PFO was almost 100% head-to-tail structure, and it was a good plasticizer and thermal stabilizer for poly(propylene carbonate)(PPC), an alternate copolymer of propylene oxide and carbon dioxide. For PFO/PPC polyblend with PFO loading of 2 wt%, its Td increased by 50 °C from 214 °C of pure PPC to 264 °C, while its elongation at break increased from 13% of pure PPC to 29%.

ChemInform Abstract: On the Utility of S‐Mesitylsulfinimines for the Stereoselective Synthesis of Chiral Amines and Aziridines.

AbstractThe S‐mesitylsulfinimines are a useful alternative.

Synthesis of poly(2‐furyloxirane) with high molecular weight and improved regioregularity using macrocyclic ether as a cocatalyst to potassium tert‐butoxide

Abstract2‐Furyloxirane (FO), a monomer usually obtained from a nonpetroleum route, was prepared from the epoxidation reaction of furfural and trimethylsulfonium chloride. About 200–300 g FO can be obtained in each preparation process. Although anionic polymerization of FO generally gives low‐ molecular‐weight polymers even after long periods of polymerization, the reaction was greatly improved when macrocyclic ether was used as a cocatalyst to potassium tert‐butoxide. When 18‐crown‐6 was used as a cocatalyst, poly(2‐furyloxirane) (PFO) with a number‐average molecular weight (Mn) of 41.5 kg/mol and a polydispersity index of 1.3 was obtained at 94% yield after polymerization at 40 °C for 72 h. The PFO obtained contained a 61.7% head‐to‐tail (H‐T) structure in the absence of the macrocyclic ether, and it reached 70.6% when cryptand[2,2,2] was used as a cocatalyst. PFO with higher regioregular structures showed improved thermal properties. For PFO with Mn of around 20.0 kg/mol, its glass transition temperature (Tg) increased from −3 to 6 °C when the H‐T content was increased from 61.7 to 70.6%. Raising the Mn of PFO also raised Tg. For PFO with 68.9% H‐T structure, its Tg could reach 7 °C when Mn was increased to 40 kg/mol. This study shows two effective ways to improve the thermal and mechanical performances of the polymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

On the utility of S-mesitylsulfinimines for the stereoselective synthesis of chiral amines and aziridines

The synthetic utility of S-mesitylsulfinimines for the synthesis of chiral amines and aziridines was examined through their reactions with Grignard reagents, with the ylides derived from trimethylsulfonium iodide and S-allyl-tetrahydrothiophenium bromide and through an aza-Darzens manifold, affording convenient access to a diverse range of highly substituted chiral amines and aziridines in high yields and excellent stereoselectivities.

ChemInform Abstract: A New Efficient Route to the Phenolic Derivatives of Chrysene and 5-Methylchrysene, Precursors to Dihydrodiol and Diol Epoxide Metabolites of Chrysene and 5-Methylchrysene, Through Suzuki Cross-Coupling Reaction.

A new, abbreviated synthesis of 5-methylchrysene (17), 2-hydroxychrysene (16), 8-hydroxy-5-methylchrysene (23), and 2-hydroxy-5-methylchrysene (24) is reported. The phenolic derivatives 16, 23, and 24 can easily be converted to carcinogenic dihydrodiol and diol epoxide metabolites of chrysene and 5-methylchrysene. The method entails the initial Suzuki cross-coupling reaction of naphthalene-2-boronic acid (1) and/or 6-methoxynaphthalene-2-boronic acid (2) with 2-bromo-5-methoxybenzaldehyde (3), methyl 2-bromophenylacetate (4), 2-bromophenylacetone (5), and/or 2-iodo-5-methoxyphenylacetone (6) to produce 2-(2-naphthyl)-5-methoxybenzaldehyde (7), methyl 2-(6-methoxy-2-naphthyl)phenylacetate (8), 2-(2-naphthyl)phenylacetone (9), 2-(2-naphthyl)-5-methoxyphenylacetone (10), and 2-(6-methoxy-2-naphthyl)phenylacetone (11) in 55–98% yields. 2-Methoxychrysene (15) was obtained with high regioselectivity by two different procedures. In the first procedure, the aldehyde function of 7 was elongated with trimethylsulfonium iodide under phase transfer conditions to generate the ethylene oxide 12 which after methanesulfonic acid treatment produced 15. The second procedure involved modification of ester 8 to its aldehyde analogue 14 which was subsequently treated with methanesulfonic acid to produce 15. Phenylacetone 10 was converted by methanesulfonic acid treatment into 8-methoxy-5-methylchrysene (18) with 90% regioselectivity. However, the similar cyclization of phenylacetones 9 and 11 to 5-methylchrysene (17) and 2-methoxy-5-methylchrysene (19) occurred with only 33–50% regioselectivity. The separation of 17 and 19 from their chromatographically similar 6-methylbenz[a]anthracene byproducts 20 and 22 was readily achieved by a chemical method. The methoxy derivatives of chrysene were finally demethylated with boron tribromide to the corresponding phenolic compounds in 90–98% yields.

ChemInform Abstract: Urea Derivatives Are Highly Active Catalysts for the Base‐Mediated Generation of Terminal Epoxides from Aldehydes and Trimethylsulfonium Iodide.

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Urea derivatives are highly active catalysts for the base-mediated generation of terminal epoxides from aldehydes and trimethylsulfonium iodide

N,N'-Diarylureas have been shown to efficiently catalyse sulfonium ylide-mediated aldehyde epoxidation reactions for the first time. These processes are of broad scope and can be coupled with a subsequent Cu(II) ion-catalysed Meinwald rearrangement to give an efficient and convenient protocol for aldehyde homologation without intermediate purification.

Syntheses and Crystal Structures of New Palladium(II) and Platinum(IV) Trialkylsulfonium Compounds

Abstract The reactions of platinum(II) iodide with triethyl‐ or trimethylsulfonium iodide in acetonitrile solution lead to the formation of crystalline products (Et3S)2[PtI6] (1) and [Me3S]2[PtI6]·CH3CN (2), respectively. The formation of Pt(IV) complexes may be explained either by disproportionation of PtI2 or oxidation by oxygen. Palladium(II) iodide reacts with triethylsulfonium iodide to give the palladium(II) complex (Et3S)2[PdI4] (3). The crystal structures of 1–3 were determined by single‐crystal X‐ray diffraction. In the crystal structures, the compounds 2 and 3 exhibit an extensive hydrogen‐bonding network.

Direct Synthesis of Chiral Aziridines from N‐tert‐Butyl‐sulfinylketimines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Direct synthesis of chiral aziridines from N-tert-butyl-sulfinylketimines.

The direct preparation of a range of variously substituted chiral tert-butylsulfinylketimines was achieved in good yield (41-90%), with relatively rapid reaction times (4-15 hours); their synthetic application was examined through the reaction with the ylides derived from trimethylsulfonium iodide and S-allyl tetrahydrothiophenium bromide, affording convenient access to a diverse range of highly substituted chiral aziridines in up to 78% yield and > 90% d.e.

Facile Preparation of Trimethylsulfonium Bromide

Trimethylsulfonium bromide, utilized to make oxiranes and molten salts, has been reported to be prepared from dimethyl sulfoxide and ethyl bromoacetate, alkyl halide and dimethyl sulfide, and dimethyl sulfoxide and bromine. Herein, we report a very simple and convenient method of trimethylsulfonium bromide from a modified Kornblum oxidation condition. Typical Kornblum oxidation is referred to a reaction in which alkyl/aryl halide (tosylate) is reacted with dimethyl sulfoxide followed by a direct workup procedure in basic aqueous solution to prepare corresponding aldehyde (path 1 in Figure 1). However we have found that Kornblum oxidation in the absence of water and base afforded colorless crystalline trimethylsulfonium bromide in about 65% yields after recrystallization. The X-ray crystallographic and NMR data of trimethylsulfonium bromide were consistent with those of the published report. Several pathways can be envisaged for the formation of trimethylsulfonium bromide in our conditions. However we believe that a path 2 in Figure 1 could be a major route in our acidic conditions based on control experiments. We found out that volatile products (methyl bromide, dimethyl sulfide, and hydrogen bromide) were efficiently made in our conditions. That is, we were able to isolate a mixture of aniline hydrobromide and N-methylaniline which was formed in an aniline trap attached at the outlet of reflux condenser. In an another experiment we could observe and collect solid trimethylsulfonium bromide (about 1 gm) formed in a reservoir attached between the reaction flask and reflux condenser, which gave us an information that methyl bromide and dimethyl sulfide were obviously generating in an appreciable amount in our reaction conditions. Supposing a path 2 in Figure 1 to be a major route, then one might ask for the verification of benzyl methanesulfenate. We tried to get any evidence for the existence of benzyl methanesulfenate by both NMR and GC/MS, only to fail. We believe that benzyl methanesulfenate can not survive our acidic conditions. Instead we found out that benzyl methyl sulfide and dibenzyl sulfide were formed. In order to get more pieces of evidence related with this modified Kornblum oxidation reactions, reactions of benzyl bromide with diphenyl sulfoxide and methyl phenyl sulfoxide were carried out. As shown in Figure 2, reactions of benzyl bromide with either diphenyl sulfoxide and methyl phenyl sulfoxide turned out to be very clean by NMR. Trimethylsulfonium bromide was not formed at all in these reactions. Noteworthy was that further oxidation proceeded in reaction of diphenyl sulfoxide to give benzoic acid, instead of benzaldehyde obtained in the reaction of methyl phenyl Figure 1. Reaction of benzyl bromide and dimethyl sulfoxide.

Derivatization of Acidic Herbicides with Selected Tetraalkyl Ammonium and Trimethyl Sulfonium Hydroxides for Their GC Analysis

This work presents studies on phenoxy acid [MCPP—2‐(4‐chloro‐2‐methylphenoxy)propanoic acid; MCPA—(4‐chloro‐2‐methylphenoxy)acetic acid; 2,4‐D‐2,4‐dichlorophenoxyaceticacid; 2,4,5‐T‐(2,4,5‐trichlorophenoxy)acetic acid] and phenolic [PCP—pentachlorophenol, dinoterb‐2‐(1,1‐dimethylethyl)‐4,6‐dinitrophenol, dinoseb‐2‐(1‐methylpropyl)‐4,6‐dinitrophenol] herbicides with derivatization aimed at their gas chromatographic determination. The derivatization was performed in an injection port of a gas chromatograph with trimethylphenylammonium hydroxide (TMPH), trimethylsulfonium hydroxide (TMSH), and tetramethylammonium hydroxide (TMAH). The effects of temperature of the injection port, reaction medium (solvent), and reagent excess on derivatization yield were investigated. TMPH in 20‐fold excess in methanol was selected for analysis. Dichloromethane was also found to be an appropriate solvent. Repeatability of the results was poor when tert‐butyl methyl ether (MTBE) was used as reaction medium.

Synthesis of 2,4-disubstituted furans and 4,6-diaryl-substituted 2,3-benzo-1,3a,6a-triazapentalenes

Reactions of acylacetylenes 1a-h with benzotriazole 2 give intermediates 3a-h. The treatment of 3a-h with trimethylsulfonium iodide in the presence of base give intermediate oxiranes 4a-h and 2,3-benzo-1,3a,6a-triazapentalenes 7d-g depending on substituent. Acid-catalyzed rearrangement of crude 4a-h give 2,4-disubstituted furans 5a-h.

The First Corey—Chaykovsky Epoxidation and Cyclopropanation in Ionic Liquids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Syntheses of 3-hydroxymethyl-2,3-dihydrobenzofurans and 3-hydroxymethylbenzofurans

Reactions of 2-hydroxyphenylmethanones 8 with 1-chloro-1-(benzotriazol-1-yl)alkanes 9 give intermediates 10a-h , which were converted by trimethylsulfonium iodide to oxirans 11a-h. Treatment of 11a-h with LDA gave either 3-hydroxymethyl-2,3-dihydrobenzofurans or 3- hydroxymethylbenzofurans depending on substituents. Benzofurans undergo electrophilic substitution at the 2-position, and this normally precludes the direct introduction of a 3-substituent. Available methods for the preparation of 3- hydroxymethylbenzofurans 1 include (i) ring syntheses which often involve multi-step reactions, 5,7 e.g. via benzofuran-2,3-dicarboxylic acid 2; (ii) Pd-catalyzed heteroannulation of 2- iodophenols 3 with O-silyl protected alkynols, 8 or from 3-(2-bromophenoxy)acrylic ester 4; 3 (iii) cyclization of 1-(2-(2-propynyloxy)phenyl)diazonium salts 5; 9 (iv) reaction of O-silyl protected 2-ethynylphenols 6 with aldehydes under TBAF catalysis; 10 (v) oxidation of 3- methylbenzofurans 7 with selenium dioxide followed by reduction with LAH; 11 and (vi)

The first Corey–Chaykovsky epoxidation and cyclopropanation in ionic liquids

The first Corey–Chaykovsky epoxidation and cyclopropanation using trimethyl sulfonium iodide/trimethyl sulfoxonium iodide and KOH as base in the recyclable ionic liquid, (bmim)PF 6 are described.