Elimination Of Sulfur Dioxide Research Articles

Synthesis and DFT conformational analysis of trimethyl-functionalized [2.2]metacyclophanes and their Lewis-acid assisted reactions

The synthesis of the strained trimethyled anti-[2.2]metacyclophanes 5a and 5b is reported. They were synthesized by ring contraction of the corresponding unstrained cyclic precursors 2,11-dithia[3.3]metacyclophane-2,2,11,11-tetraoxides, 4a and 4b by the vacuum-pyrolysis elimination of sulfur dioxide ("sulfone pyrolysis‘).Tetraoxides 4a and 4b were generated by the oxidation of their respective dithia[3.3]metacyclophane precursors 3a and 3b. The macrocyclic coupling reactions which formed 3a and 3b also produced both anti- and syn-conformational isomers which could be separated from their respective reaction mixtures and whose structures were confirmed by 1H-NMR spectroscopy. Single-crystal X-ray analyses confirmed the anti conformation of anti-3b in the solid state and that the corresponding oxidized tetraoxide, syn-4b adopts a syn conformation. The Lewis acid (TiCl4/AlCl3-MeNO2)-catalyzed reactions of anti-5b under various conditions led to transannular cyclization to afford tetrahydropyrene 7, pyrene derivative 8 and/or de-tert-butylated anti-5a. A DFT (Density Functional Theory) computational study was conducted to determine the stabilities of the different conformational isomers of the target compounds.

Rhodium(III)‐Catalyzed Heteroannulations of 3‐Sulfolene Derivatives through C(sp2)−H Activation: Access to Pyridine ortho‐Quinodimethane Precursors

AbstractHydroxamates derived from 3‐sulfolene‐3‐carboxylic acid can be involved in intra‐ and intermolecular rhodium(III)‐catalyzed heteroannulations with alkynes proceeding through C(sp2)−H bond activation. These transformations allow for a straightforward access to diversely substituted pyridones, and to pyridines fused to a sulfolene ring after functional group transformations. Subsequent cheletropic elimination of sulfur dioxide can be achieved under microwave irradiation to generate pyridine ortho‐quinodimethanes. These results demonstrate that the scope of rhodium(III)‐catalyzed C(sp2)−H functionalizations can be extended to sulfolenes, a yet unexplored class of alkenes in these latter transformations, thereby affording access to valuable classes of heterocyclic products.

Solidothermal synthesis of nitrogen-decorated, ordered mesoporous carbons with large surface areas for efficient selective capture and separation of SO2

As a typical corrosive and toxic exhaust gas, the effective elimination of sulfur dioxide is of great importance for flue gas desulfurization. Yet the facile synthesis of adsorbents with high capture capacity (especially at low partial pressures) as well as excellent stability remains a challenge. Herein, we reported the preparation of N-functionalized ordered mesoporous carbons through a solvent-free self-assembly strategy for selective capture and separation of SO2 via enhanced base-acid host–guest interaction. The N-doped ordered mesoporous carbons were synthesized using Pluronic F127, terephthalaldehyde, and m-aminophenol as raw materials, then followed by activation with KOH. The synthesized N-OMC-T samples are found to exhibit large specific surface areas (∼1191 m2/g) and multifunctional nitrogen base sites. The synthesized K-N-OMC-T samples show excellent SO2 capacity with 13.15 mmol/g at 1.0 bar and 25 °C, and the corresponding IAST selectivities for SO2/N2 and SO2/CO2 reach up to 195.8 and 16.4 (25 °C), respectively. The breakthrough tests further demonstrate the impressive elimination of SO2 from SO2/CO2/N2 gas mixture by K-N-OMC-T samples. Thus, it is believed that the possibility for selective SO2 capture from flue gas is for K-N-OMC-T samples.

Deep Desulfurization with Record SO2 Adsorption on the Metal-Organic Frameworks.

Selective elimination of sulfur dioxide is significant in flue gas desulfurization and natural gas purification, yet developing adsorbents with high capture capacity especially at low partial pressure as well as excellent cycling stability remains a challenge. Herein, a family of isostructural gallate-based MOFs with abundant hydrogen bond donors decorating the pore channel was reported for selective recognition and dense packing of sulfur dioxide via multiple hydrogen bonding interactions. Multiple O···H-O hydrogen bonds and O···H-C hydrogen bonds guarantee SO2 molecules are firmly grasped within the framework, and appropriate pore apertures afford dense packing of SO2 with high uptake and density up to 1.86 g cm-3, which is evidenced by dispersion-corrected density functional theory calculations and X-ray diffraction resolution of a SO2-loaded single crystal. Ultrahigh adsorption uptake of SO2 at extremely low pressure (0.002 bar) was achieved on Co-gallate (6.13 mmol cm-3), outperforming all reported state-of-the-art MOFs. Record-high IAST selectivity of SO2/CO2 (325 for Mg-gallate) and ultrahigh selectivity of SO2/N2 (>1.0 × 104) and SO2/CH4 (>1.0 × 104) were also realized. Breakthrough experiments further demonstrate the excellent removal performance of trace amounts of SO2 in a deep desulfurization process. More importantly, M-gallate shows almost unchanged breakthrough performance after five cycles, indicating the robust cycling stability of these MOFs.

Nanomolar Detection of H2S in an Aqueous Medium: Application in Endogenous and Exogenous Imaging of HeLa Cells and Zebrafish.

The homeostasis of short-lived reactive species such as hydrogen sulfide/hypochlorous acid (H2S/HOCl) in biological systems is essential for maintaining intercellular balance. An unchecked increase in biological H2S concentrations impedes homeostasis. In this report, we present a molecular probe pyrene-based sulfonyl hydrazone derived from pyrene for the selective detection of H2S endogenously as well as exogenously through a “turn-off” response in water. The structure of the receptor is confirmed by Fourier-transform infrared spectroscopy, 1H and 13C nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction studies. The receptor shows excellent green emission in both the aqueous phase and solid state. Quenching of green emission of the receptor is observed only when H2S is present in water with a detection limit of 18 nM. Other competing anions and cations do not have any influence on the receptor’s optical properties. The efficiency of H2S detection is not negatively impacted by other reactive sulfur species too. The sensing mechanism of H2S follows a chemodosimetric reductive elimination of sulfur dioxide, which is supported by product isolation. The receptor is found to be biocompatible, as evident by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and its utility is extended to endogenous and exogenous fluorescence imaging of HeLa cells and zebrafish.

Nicosulfuron Degradation by an Ascomycete Fungus Isolated From Submerged Alnus Leaf Litter.

Nicosulfuron is a selective herbicide belonging to the sulfonylurea family, commonly applied on maize crops. Its worldwide use results in widespread presence as a contaminant in surface streams and ground-waters. In this study, we isolated, for the first time, the Plectosphaerella cucumerina AR1 nicosulfuron-degrading fungal strain, a new record from Alnus leaf litter submerged in freshwater. The degradation of nicosulfuron by P. cucumerina AR1 was achieved by a co-metabolism process and followed a first-order model dissipation. Biodegradation kinetics analysis indicated that, in planktonic lifestyle, nicosulfuron degradation by this strain was glucose concentration dependent, with a maximum specific degradation rate of 1 g/L in glucose. When grown on natural substrata (leaf or wood) as the sole carbon sources, the Plectosphaerella cucumerina AR1 developed as a well-established biofilm in 10 days. After addition of nicosulfuron in the medium, the biofilms became thicker, with rising mycelium, after 10 days for leaves and 21 days for wood. Similar biofilm development was observed in the absence of herbicide. These fungal biofilms still conserve the nicosulfuron degradation capacity, using the same pathway as that observed with planktonic lifestyle as evidenced by LC-MS analyses. This pathway involved first the hydrolysis of the nicosulfuron sulfonylurea bridge, leading to the production of two major metabolites: 2-amino-4,6-dimethoxypyrimidine (ADMP) and 2-(aminosulfonyl)-N,N-dimethyl-3-pyridinecarboxamide (ASDM). One minor metabolite, identified as 2-(1-(4,6-dimethoxy-pyrimidin-2-yl)-ureido)-N,N-dimethyl-nicotinamide (N3), derived from the cleavage of the C-S bond of the sulfonylurea bridge and contraction by elimination of sulfur dioxide. A last metabolite (N4), detected in trace amount, was assigned to 2-(4,6-dimethoxy-pyrimidin-2-yl)-N,N-dimethyl-nicotinamide (N4), resulting from the hydrolysis of the N3 urea function. Although fungal growth was unaffected by nicosulfuron, its laccase activity was significantly impaired regardless of lifestyle. Leaf and wood surfaces being good substrata for biofilm development in rivers, P. cucumerina AR1 strain could thus have potential as an efficient candidate for the development of methods aiming to reduce contamination by nicosulfuron in aquatic environments.

Kinetic Study of Sulfur Dioxide Elimination by Limestone through the Lab Scale Circulating Fluidized Bed Combustor

Characteristics of sulfur dioxide emission from coal and petroleum coke combustion were examined in a lab scale circulating fluidized bed (CFB) combustor. The rate constant of the first order rate expression for the absorption SO2 on the CaO surface was similar regardless of the origin of the limestone, the particle size and the initial SO2 concentration. However, the total SO2 absorption capacity was different depending on the origin of the limestone. The breakability of the particle which provides new surface for the reaction seems to play a major role in the absorption characteristics.

Highly Efficient and Stereoselective Julia–Kocienski Protocol for the Synthesis of α‐Fluoro‐α,β‐unsaturated Esters and Weinreb Amides Employing 3,5‐Bis(trifluoromethyl)phenyl (BTFP) Sulfones

Abstractα‐Fluoroacetates 3 and Weinreb amide 4, bearing a α‐[3,5‐bis(trifluoromethyl)phenyl]sulfonyl (BTFP‐sulfonyl) group at the α‐position, are employed in the highly stereoselective synthesis of α‐fluoro‐α,β‐unsaturated alkenoates and Weinreb amides, respectively. Aromatic and aliphatic aldehydes are condensed under extremely mild and simple reaction conditions using potassium carbonate in dimethylformamide at room temperature under solid‐liquid phase‐transfer catalysis conditions in good yields and high Z‐diastereoselectivities, specially in the case of the fluorinated Weinreb amides. A detailed computational mechanistic study suggests a final non‐concerted elimination of sulfur dioxide and 3,5‐bis(trifluoromethyl)phenoxide and explains the observed high stereoselectivities for the reaction on the basis of thermodynamic and kinetic considerations.

A facile synthesis of 5(6)‐(chloromethyl)benzimidazoles: Replacement of a sulfonic acid functionality by chlorine

Abstractmagnified imageValuable new synthetic intermediates, 5(6)‐(chloromethyl)benzimidazoles, were prepared by the facile elimination of sulfur dioxide under the influence of thionyl chloride from benzimidazole‐5(6)‐methane‐sulfonic acids easily obtained from (3,4‐diaminophenyl)methanesulfonic acid with formic‐, or trifluoroacetic acid. Both reaction steps involved only acidic conditions, thus the synthesis of polysubstituted 5(6)‐(chloromethyl)benzimidazoles incorporating base‐sensitive substituents became possible.

Reactions of electron-withdrawing thiophene 1,1-dioxides with furans. A novel reaction pathway

Reactions of thiophene dioxides containing electron-withdrawing substituents with furans were studied. The reactions with unsubstituted furan followed the inverse-electron-demand Diels-Alder mechanism. Subsequent elimination of sulfur dioxide from the adduct afforded products of the tetrahydrobenzofuran series. The reactions with substituted furans gave benzylcarbonyl compounds in high yields. The observed regiochemistry of the reaction was explained in terms of the frontier orbital theory using the calculated orbital coefficients.

Efficient desulfurization of 2-thiopyrimidine nucleosides to the corresponding 4-pyrimidinone analogues using trans-2-(phenylsulfonyl)-3-phenyloxaziridine

A brief treatment of 2-thiopyrimidine nucleosides (s 2U ∗) with trans-2-phenylsulfonyl-3-phenyloxaziridine (PSO) results in efficient substrate desulfurization leading to the corresponding 4-pyrimidinone analogues (H 2U ∗). The key transformation proceeds through oxidation of the 2-thiocarbonyl group to a sulfur oxyacid derivative and subsequent elimination of sulfur dioxide. 4-Pyrimidinone 1-β- d-riboside (H 2U) has been transformed into the respective phosphoramidite, a ready-to-use monomer for the introduction of a modified nucleoside into an oligonucleotide chain. Moreover, the effective desulfurization of the 2-thiouridine nucleotide could be achieved directly at the oligonucleotide level, by treatment of the TdA(s 2U)dGdC oligonucleotide with PSO, as verified by MALDI-TOF mass spectrometry.

A Convergent, Flexible Synthesis of 1,3‐Dienes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A convergent, flexible synthesis of 1,3-dienes.

1,3-Dienes were prepared from 1,4-ketoxanthates, obtained by the radical addition reaction of an S-(2-oxoalkyl) xanthate to a terminal olefin, through the DBU induced thermal elimination of sulfur dioxide from the derived 2-sulfolenes.

Decomposition of 3,5-diaryloxathiolane-2-oxides under electron impact

1,2-diarylcyclopropanes are known to form the corresponding 3,5-diaryl-1,2-oxathiolane-oxides upon reaction with sulfur dioxide in the presence of trifluoroacetic acid. The reverse reaction, the elimination of sulfur dioxide from 3,5-diaryl-1,2-oxathiolane-2-oxides to form the corresponding 1,2-diarylcyclopropanes, is also known in organic chemistry. In the present work, the loss of sulfur dioxide from the molecular ion of 3,5-diphenyl-1,2-oxathiolane-2-oxide ( 1), 3-phenyl-5-(p-methoxyphenyl)-1,2-oxathiolane-2-oxide ( 2), and 3,5-di-(p-methoxy phenyl)-1,2-oxathiolane-2-oxide ( 3) was observed in the ion source of a mass spectrometer under electron impact ionization conditions (EI). The resulting (M-SO 2) + ions had the same collisional activation mass spectra as the cation-radicals of the authentic 1,2-diphenylcyclopropane ( 4), 1-(p-methoxyphenyl)-2-phenylcyclopropane ( 5), and 1,2-(p-methoxyphenyl) cyclopropane ( 6), respectively, indicating their common structure. Therefore, the molecular ions of 1,2-oxathiolane-2-oxides 1–3 lose SO 2 to give rise to pseudomolecular ions of diarylcyclopropanes 4–6. The fragmentation reactions of 1,2-diphenylcyclopropane (compound 4) under EI were studied in detail using tandem mass spectrometry and high resolution mass spectrometry in order to establish their ion structure and fragmentation mechanisms. Our data suggests that the cation radicals of diphenylcyclopropane isomerize giving primarily cation-radicals of a methyldihydrophenanthrene structure. The latter undergoes dissociation to give rise to protonated phenanthrene ( m / z = 179), fluorenyl-cation ( m / z = 165) and indenyl-cation ( m / z = 115). Since SO 2 elimination from 3,5-diaryl-1,2-oxathiolane-2-oxides to form diarylcyclopropanes takes place both in solution and in the gas phase under EI, the compounds under study can serve as examples of a system in which a condensed phase reactions parallel cation radical reactions within the ion source of a mass spectrometer.

Cationic Ring-Opening Polymerization Behavior of Six-Membered Cyclic Sulfite

Cationic ring-opening polymerization behavior of six-membered cyclic sulfite (1) was examined. 1 was prepared by the reaction of 1,3-propanediol with SOCl 2 in 80% yield. Cationic ring-opening polymerization of 1 was carried out in the presence of cationic initiators such as benzyl bromide (BnBr), BF 3 .OEt 2 , trifluoromethanesulfonic acid (TfOH), and methyl trifluoromethanesulfonate (TfOMe) in bulk to afford a polymer consisting of sulfite and ether moieties. The content of the poly(ether) unit was estimated to be 30-90%. The relative rate of polymerization by the initiators was estimated to be TfOH :TfOMe :BF 3 .OEt 2 = 3.5 :2.5 :1.0. Judging from the time-conversion curves and time-poly(ether) production curves, the elimination of sulfur dioxide in the propagating end of the polymer was confirmed to depend on the character of the counteranion.

Comparison of the reactivity of thiophene, thiophene 1‐oxide, and thiophene 1,1‐dioxide as diene for diels‐alder reactions. An ami semiempirical study

AbstractA semiempirical AMI theoretical study was carried out to examine the very low reactivity of thiophene; for example, the high reactivity of thiophene 1‐oxide as a diene in the Diels Alder reactions. The reactivities of cyclopentadiene, thiophene, thiophene 1‐oxide, and thiophene 1,1‐dioxide were studied as dienes in the reaction with ethylene, cyclopropene, and benzoquinone. Ethylene was chosen as a standard, while cyclopropene, with its high strain energy was released in the course of a reaction making it relatively reactive. The benzoquinone has a lower LUMO energy, making it a very reactive dienophile for the Diels‐Alder reaction. Frontier molecular orbital energy gap between the reactants was considered, and the disadvantage of this approach in studying the reactivity was demonstrated. For all combinations, the corresponding transition structures are generated and the activation energies are estimated. The estimated activation barrier for sulfur dioxide elimination from the adduct was used to explain the failure to accumulate the cycloadduct in the reaction mixture. The obtained results are compared with experimental data when available. An excellent agreement of theory and experiment was obtained.

Generation and reactions of aza- ortho-xylylenes in the injector of GC/MS system

Nitro derivatives of 2,1-benzisothiazoline 2,2-dioxide (benzosultams) undergo thermal elimination of sulfur dioxide yielding very reactive, non-isolable azo- ortho-xylylenes. It was found that this reaction can be performed in the injector of the gas chromatograph at 300 – 350°C and the formed aza- ortho-xylylenes can be trapped by appropriate reagents added to the injected solution. In the preliminary experiments aza- ortho-xylylenes were reacted with dienophiles (methyl acrylate, dimethyl maleate, vinyl acetate, N-phenylmaleimide etc.) resulting in the formation of the [4+2] cycloaddition reaction products, and also with nucleophilic reagents (alcohols, amines) to give appropriate adducts. In the absence of the trapping reagent dimers of aza- ortho-xylylenes were formed.

Episulfone α-anions: Preparation and synthetic applications

Monosilyl-, monostannyl-, disilyl- and distannyl-episulfones have been prepared by episulfone α-anion generation followed by trapping with the appropriate electrophilic reagent. Elimination of sulfur dioxide provides a new route for the preparation of vinyl silanes and vinyl stannanes.

Diels-Alder Reaction of 3,5-Dihydro-1H-thieno[3,4-c]pyrrole 2,2-Dioxides with Alkene Dienophiles; Facile Preparation of 4,5,6,7-Tetrahydroisoindoles

3,5-Dihydro-1H-thieno[3,4-c]pyrrole 2,2-dioxides 3 when heated with alkene dienophiles sequentially underwent a Diels-Alder reaction on the pyrrole moiety, a cheletropic elimination of sulfur dioxide, a Diels-Alder reaction of the resulting diene, and a retro Diels-Alder reaction to give 4,5,6, 7-tetrahydroisoindoles 7-9 in excellent yields.

Pyrimidine o-quinodimethanes: Formation of 1:1 and 2:1 adducts with dienophiles

Pyrimidine fused dihydrothiophene S,S-dioxides 7 undergo thermal elimination of sulfur dioxide to give the pyrimidine o-quinodimethanes 8 which can be intercepted in Diels-Alder reactions to give substituted 5,6,7,8-tetrahydroquinazolines; these form cyclooctapyrimidines on heating with more dienophile.