Extrusion Of Sulfur Dioxide Research Articles

Sulfadiazine degradation by hydroxyl radical and direct electron transfer pathways in the self-prepared boron doped diamond electrochemical process

Sulfonamide antibiotics are frequently detected in livestock wastewater, seriously harming the ecological environment and human health. Boron-doped diamond (BDD) electrochemical process has prominent potential in degrading organic pollutants from special industrial wastewater. In this work, the degradation efficiency and mechanism for sulfadiazine (SDZ) with the prepared BDD electrode were investigated. Scanning electron microscopy (SEM) and Raman spectroscopy revealed a 2 μm thick, compact, and crack-free BDD film on silicon. The BDD's oxygen evolution potential was 1.47 V. About 93.3 % of SDZ in the synthetic wastewater was removed under the conditions of a current density of 40 mA/cm2, electrode spacing of 20 mm, electrolyte concentration of 40 mM, and an initial pH of 8. Hydroxyl radical and direct electron transfer (DET) mainly contributed to SDZ degradation based on specific quencher tests and electrochemical analysis. The possible transformation pathways of SDZ were proposed according to the detected oxidation products and DFT calculation, mainly including amino hydroxylation, sulfur dioxide extrusion, and pyrimidine heterocyclic ring opening. Furthermore, the toxicity of intermediates products markedly weakened compared to that of SDZ. The presence of ion chloride could slightly improve the removal of SDZ, while bicarbonate and phosphate inhibited the SDZ degradation. In addition, the efficient removal of chemical oxygen demand and SDZ in the effluent of aerobic biological treatment effluent of actual livestock wastewater was confirmed. To sum up, BDD electrochemical oxidation is a viable approach for the advanced treatment of livestock wastewater.

Silyloxymethylation of Aryl Halides via Metallaphotoredox Catalyzed Desulfinative Cross‐Coupling with Silyl Rongalite

AbstractA visible‐light‐triggered silyloxymethylation of aryl halides has been developed by the merger of photoredox and transition metal catalysis. Under the Ru/Ni dual catalytic conditions, sodium tert‐butyl‐dimethylsilyloxymethanesulfinate (SOMS) undergoes facile extrusion of sulfur dioxide to engender a silyloxymethyl radical that engages in the cross‐coupling with a range of aryl halides to produce benzyl silyl ether derivatives. The protocol is also effective with alkenyl halides and triflates, thus offering an efficient synthetic approach to the silyl‐protected allylic alcohols.

From micro to macro: The role of seawater in maintaining structural integrity and bioactivity of granules in treating antibiotic-laden mariculture wastewater

Granular sludge (GS) has superior antibiotic removal ability to flocs, due to GS's layered structure and rich extracellular polymeric substances. However, prolonged exposure to antibiotics degrades the performance and stability of GS. This study investigated how a seawater matrix might help maintain the structural integrity and bioactivity of granules. The results demonstrated that GS had better sulfadiazine (SDZ) removal efficiency in a seawater matrix (85.6 %) than in a freshwater matrix (57.6 %); the multiple ions in seawater enhanced boundary layer diffusion (kiR1 = 0.0805 mg·g−1·min−1/2 and kiR2 = 0.1112 mg·g−1·min−1/2) and improved adsorption performance by 15 % (0.123 mg/g-SS freshwater vs. 0.141 mg/g-SS seawater). Moreover, multiple hydrogen bonds (1–3) formed between each SDZ and lipid bilayer fortified the adsorption. Beyond S-N and S-C bond hydrolyses that took place in freshwater systems, there was an additional biodegradation pathway for GS to be cultivated in a saltwater system that involved sulfur dioxide extrusion. This additional pathway was attributable to the greater microbial diversity and larger presence of sulfadiazine-degrading bacteria containing SadAC genes, such as Leucobacter and Arthrobacter, in saltwater wastewater. The findings of this study elucidate how seawater influences GS properties and antibiotic removal ability.

An Unexpected Synthesis of Crowded Triphenylenes

AbstractIn attempts to make octaphenyldibenzofuran (7) and octaphenyldibenzothiophene (8), 2,5‐dibromofuran (4) and 2,5‐dibromothiophene (5), respectively, were heated with tetracyclone (2) under forcing conditions, but only single addition products, such as 2‐bromo‐4,5,6,7‐tetraphenylbenzofuran (10) and 2‐bromo‐4,5,6,7‐tetraphenylbenzothiophene (12) were observed. However, when 2,5‐dibromothiophene‐1,1‐dioxide (6) was heated with tetracyclone, the chief product was 1,2,3,4,6,7,8‐heptaphenyltriphenylene (14). Similarly, when compound 6 was heated with acecyclone (15), the product was 11,18,20‐triphenyldiacenaphtho[a,h]triphenylene (16). Both 14 and 16 have been characterized by X‐ray crystallography. They are proposed to form from double Diels‐Alder addition products of the cyclopentadienones by extrusion of sulfur dioxide and rearrangement of the resulting radicals.

Fluorinated Sulfinates as Source of Alkyl Radicals in the Photo‐Enantiocontrolled β‐Functionalization of Enals

AbstractThe generation of sulfonyl radicals has long been known as a flexible strategy in a wide range of different sulfonylative transformations. Meanwhile their use in alkylation processes has been somehow limited due to their inherent difficulty in evolving to less‐stable radicals after sulfur dioxide extrusion. Herein we report a convenient strategy that involvesgem‐difluorinated sulfinates as an “upgrading‐mask”, allowing these precursors to decompose into their corresponding alkyl radicals. The electron–donor character of sulfinates in the formation of an electron donor–acceptor (EDA) complex with transient iminium ions is displayed, achieving the first example of a stereocontrolled light‐driven insertion ofgem‐difluoro derivatives into unsaturated aldehydes. This methodology is compatible with flow conditions, maintaining identical levels of enantiocontrol.

Fluorinated Sulfinates as Source of Alkyl Radicals in the Photo-Enantiocontrolled β-Functionalization of Enals.

The generation of sulfonyl radicals has long been known as a flexible strategy in a wide range of different sulfonylative transformations. Meanwhile their use in alkylation processes has been somehow limited due to their inherent difficulty in evolving to less-stable radicals after sulfur dioxide extrusion. Herein we report a convenient strategy that involves gem-difluorinated sulfinates as an "upgrading-mask", allowing these precursors to decompose into their corresponding alkyl radicals. The electron-donor character of sulfinates in the formation of an electron donor-acceptor (EDA) complex with transient iminium ions is displayed, achieving the first example of a stereocontrolled light-driven insertion of gem-difluoro derivatives into unsaturated aldehydes. This methodology is compatible with flow conditions, maintaining identical levels of enantiocontrol.

Diels-Alder Cycloaddition with CO, CO2, SO2, or N2 Extrusion: A Powerful Tool for Material Chemistry.

Phenyl, naphthyl, polyarylphenyl, coronene, and other aromatic and polyaromatic moieties primarily influence the final materials’ properties. One of the synthetic tools used to implement (hetero)aromatic moieties into final structures is Diels–Alder cycloaddition (DAC), typically combined with Scholl dehydrocondensation. Substituted 2-pyranones, 1,1-dioxothiophenes, and, especially, 1,3-cyclopentadienones are valuable substrates for [4 + 2] cycloaddition, leading to multisubstituted derivatives of benzene, naphthalene, and other aromatics. Cycloadditions of dienes can be carried out with extrusion of carbon dioxide, carbon oxide, or sulphur dioxide. When pyranones, dioxothiophenes, or cyclopentadienones and DA cycloaddition are aided with acetylenes including masked ones, conjugated or isolated diynes, or polyynes and arynes, aromatic systems are obtained. This review covers the development and the current state of knowledge regarding thermal DA cycloaddition of dienes mentioned above and dienophiles leading to (hetero)aromatics via CO, CO2, or SO2 extrusion. Particular attention was paid to the role that introduced aromatic moieties play in designing molecular structures with expected properties. Undoubtedly, the DAC variants described in this review, combined with other modern synthetic tools, constitute a convenient and efficient way of obtaining functionalized nanomaterials, continually showing the potential to impact materials sciences and new technologies in the nearest future.

Recent Advances in the Synthesis and Direct Application of Sulfinate Salts

Sulfinate salts have attracted considerable attentions due to their versatile reactivity. They have emerged as highly useful building blocks for the construction of all kinds of sulfonyl‐group containing molecules, such as sulfones or sulfonamides, and for the construction of various carbon–carbon‐ and carbon–heteroatom‐bonds via sulfur dioxide (SO2) extrusion. Herein, we want to summarize the latest developments in the synthesis of sulfinate salts. Both improvement of classical methods and the development of various novel protocols will be discussed. Also selected one‐pot methods directly utilizing in situ generated sulfinate salts as intermediates will be covered in this review article.

Diels-Alder reaction of tetraarylcyclopentadienones with benzo[b]thiophene S,S-dioxides: an unprecedented de-oxygenation vs. sulfur dioxide extrusion.

Diels-Alder reaction of tetraarylcyclopentadienones with benzo[b]thiophene dioxides in xylenes at reflux led to the formation of tetra aryl-substituted dibenzothiophene as well as penta aryl-substituted benzene analogues depending on the influence of aryl substituents present on cyclopentadienones. The intermediate dihydrodibenzothiophene-dioxides underwent aromatization either through de-oxygenation or extrusion of sulfur dioxide to furnish substituted dibenzothiophenes or benzenes.

Radical Alliances: Solutions and Opportunities for Organic Synthesis

AbstractThe present account discusses in detail various mechanistic features of the degenerative radical addition‐transfer of xanthates and related thiocarbonylthio congeners and makes a comparison with the more classical Kharasch reactions to which it is similar in certain aspects. The xanthate group reacts reversibly with the ‘active’ radicals in the medium and is able to store them in a somewhat inactive form. This increases their effective lifetime in the medium and, at the same time, lowers their absolute concentration while regulating their relative concentration. These properties translate into a powerful carbon–carbon bond forming process, especially as regards intermolecular additions to electronically unbiased (‘unactivated’) alkenes. Most functional groups are tolerated, in particular polar functions that often require protection with other chemistries. This broad versatility is illustrated by examples where the xanthate addition to the alkene is combined with other, more classical reactions to provide a convergent, rapid access to a wide range of useful structures. Emphasis has been placed on the synthesis of open chain and more complex carbocycles, as well as on the transfer of chirality. These ‘radical alliances’ include organosilicon chemistry, the Diels–Alder cycloaddition and cheletropic extrusion of sulfur dioxide, the Claisen sigmatropic rearrangement, and the Horner–Wadsworth–Emmons (HWE) condensation.

Transformation of aqueous sulfonamides under horseradish peroxidase and characterization of sulfur dioxide extrusion products from sulfadiazine

The potential of horseradish peroxidase (HRP) to catalyze the removal of sulfonamides from water and the effects of different H2O2 and HRP concentrations were investigated. Six sulfonamides, each with a five- or six-membered heterocyclic group, including sulfamethoxazole (SMX), sulfathiazole (STZ), sulfapyridine (SPD), sulfadiazine (SDZ), sulfamerazine (SMR) and sulfamethoxypyridazine (SMP) were selected as target compounds. All sulfonamides exhibit a pseudo-first-order dependence of the concentration versus the reaction time. The decay rate (k, h−1) of the six sulfonamides spiked individually exhibit a trend following the order of STZ > SMP, SPD > SMR > SDZ » SMX. When spiked together, the coexistent sulfonamides might act as mediators for the enhancement of SMX removal and as competitors for the decreased removal of most sulfonamides. Moreover, six transformation products of SDZ are identified by the Thermo Scientific LTQ Orbitrap Elite technique. SDZ transformation involves two steps: one is the Smiles re-arrangement of the structure, and the other is oxidation and sulfur dioxide extrusion. This study is the first to report the removal dynamics of sulfonamides in HRP-catalyzed reactions and the identified products of SDZ.

Visible light induced Trifluoromethyl Migration: Easy Access to α‐Trifluoromethylated Ketones from Enol Triflates

AbstractHerein, we reported a novel method to synthesize α‐trifluoromethylated ketones from enol triflates. Involving a cascade sulfur dioxide extrusion and a CF3 (trifluoromethyl) radical addition process, this reaction proceeds at room temperature and is driven by visible light irradiation. This protocol bears good functional group compatibility, which can generate the desired products in good to excellent yields even in gram scale. It is hoped that this approach to generate CF3 radicals from enol triflates can be used in other radical‐involved reactions.magnified image

Syntheses of Combretastatins D-1, D-2, and D-4 via Ring Contraction by Flash Vacuum Pyrolysis.

We report the syntheses of combretastatins D-2 and D-4 as well as a formal synthesis of combretastatin D-1 by a conceptually new route harnessing a ring-contracting flash vacuum pyrolytic extrusion of sulfur dioxide from the respective 16-membered sulfone precursors. Via flash vacuum pyrolysis, even metaparacyclophanes as small and strained as the hitherto unknown oxa[1.5]metaparacyclophane could be prepared as a side product en route to combretastatin D-2 by synchronous extrusion of SO2 and CO2.

Metal Free Bi(hetero)aryl Synthesis: A Benzyne Truce–Smiles Rearrangement

AbstractA new benzyne transformation is described that affords versatile biaryl structures without recourse to transition‐metal catalysis or stoichiometric amounts of organometallic building blocks. Aryl sulfonamides add to benzyne upon fluoride activation, and then undergo an aryl Truce–Smiles rearrangement to afford biaryls with sulfur dioxide extrusion. The reaction proceeds under simple reaction conditions and has excellent scope for the synthesis of sterically hindered atropisomeric biaryl amines.

Metal Free Bi(hetero)aryl Synthesis: A Benzyne Truce-Smiles Rearrangement.

A new benzyne transformation is described that affords versatile biaryl structures without recourse to transition‐metal catalysis or stoichiometric amounts of organometallic building blocks. Aryl sulfonamides add to benzyne upon fluoride activation, and then undergo an aryl Truce–Smiles rearrangement to afford biaryls with sulfur dioxide extrusion. The reaction proceeds under simple reaction conditions and has excellent scope for the synthesis of sterically hindered atropisomeric biaryl amines.

Stereoelectronic Effects: A Powerful Concept in Explaining Kinetic and Thermodynamic Aspects of Retro Cheletropic Reactions

Kinetic and thermodynamic aspects of the retro cheletropic reaction of sulfur dioxide extrusion have been investigated. The interaction of the X–S bond (X=NH, S, O and CH2) and oxygen lone pairs of SO2 showed remarkable stereoelectronic effects and its correlation with the difference between computed and empirical bond length (Δl) have been analysed. The facility of the reaction in the case of four derivatives (X=NH, S, O and CH2) has been investigated from the viewpoint of product delocalisation energy. In addition, substitution effects have been studied on the relative Gibbs free energy of reaction for the oxygen derivative (X=O). Moreover, a correlation has been found between the Gibbs free energy of reaction in the presence of the substituent and Δl as a criterion for the value of the interaction between the X–S bond and oxygen lone pairs of the SO2 group. Finally, a new method based on electron density has been used for evaluation of the synchronicity values of the reaction. According to the corresponding diagrams, the calculated synchronicity values of the Wiberg bond indices and electron density are in good agreement.

Quantum chemical study of the photolysis mechanisms of sulfachloropyridazine and the influence of selected divalent metal ions

Sulfonamides have been found in aquatic environments. Degradation of sulfachloropyridazine (SCP) mainly proceeds through direct and indirect photolysis in the aquatic environment. However, the mechanisms underlying the triplet photolysis of SCP and the influence of metal ions on the photolysis mechanism have not yet been fully explained. In this study, we elucidated the triplet photolysis mechanisms of SCP and the effects of three selected metal ions (Zn2+, Ca2+, and Cu2+) on the SCP photolysis mechanisms using quantum chemical calculation. Optimization of molecular structures and reaction pathways analysis of SCP were carried out at the B3LYP/6-31+G(d,p) level of theory. Two minimum energy pathways were investigated in the triplet photolysis of SCP. In Step 2 of Path-I, the photolysis product of SCP is a sulfur dioxide extrusion product, (4-(3-chloro-6-iminopyridazine-1(6H)-yl)aniline). The estimated activation energies of Step 2 and Step 3 of Path-I were much higher than in Path-II. Therefore, Path-II was found as the lowest energy pathway to obtain the SCP photoproducts, and Step 2 of Path-II was confirmed as the rate-determining step (RDS) in the photolysis mechanism of SCP. For the RDS of Path-II, computations with the three metal ions complexes (IM1–Cu2+, IM1–Ca2+, and IM1–Zn2+) show that the metal ions Cu2+ and Ca2+ promote triplet-sensitized photolysis of SCP by reducing the activation energy of RDS of Path-II, whereas Zn2+ showed an inhibitory effect in photolysis of SCP by increasing the activation energy.

ChemInform Abstract: Tandem Diels—Alder and Retro‐Ene Reactions of 1‐Sulfenyl‐ and 1‐Sulfonyl‐1,3‐dienes as a Traceless Route to Cyclohexenes.

A pericyclic approach for the synthesis of six-membered ring structures is described. The method employs 1,3-dienes with a 1-sulfur substituent in a tandem sequence of Diels–Alder and retro-ene reactions. In this pairing of [4 + 2] cycloaddition and 1,5-sigmatropic rearrangement, 1-sulfenyl-1,3-dienes engage in Diels–Alder reactions with electron-deficient dienophiles. Subsequently, the sulfenyl group of the cycloadducts is oxidized and unmasked to form allylic sulfinic acids, which undergo sterospecific reductive transposition via sulfur dioxide extrusion. The sequence can also include an inverse electron demand Diels–Alder reaction by using a 1-sulfonyl-1,3-diene. This combination of two pericyclic events offers novel stereocontrolled access to cyclohexenes that are inaccessible via a direct [4 + 2] cycloaddition route.

N,N-Dialkyl-N′-Chlorosulfonyl Chloroformamidines in Heterocyclic Synthesis. Part XI. Some Substitution Reactions of Pyrazolo[1,5-b][1,2,4,6]thiatriazine 1,1-Dioxides

The recently discovered pyrazolo[1,5-b][1,2,4,6]thiatriazine template was shown to possess four nucleophilic sites (N2, N4, C5, N7) that underwent a range of substitution reactions. Methylation occurred at both N4 and N7. Alkylation with benzylic halides occurred preferentially at N7, regardless of the solvent, but also occurred at C5, N4, and N2. Similar alkylation with α-halo esters occurred at both N4 and N7, but the latter derivatives underwent a novel pyrazole ring expansion to afford pyrimido[1,6-b][1,2,4,6]thiatriazine derivatives. Bromination of pyrazolo[1,5-b][1,2,4,6]thiatriazines afforded unstable 5-bromo derivatives. Tosylation occurred selectively at C5, but in modest yield; catalysis with 1-methylimidazole also led to a low yield of the 5,5′-dimer. The action of HCl on N7-benzylated pyrazolo[1,5-b][1,2,4,6]thiatriazines readily caused extrusion of sulfur dioxide to produce pyrazolo-guanidines.

Elucidating triplet-sensitized photolysis mechanisms of sulfadiazine and metal ions effects by quantum chemical calculations

Sulfadiazine (SDZ) mainly proceeds triplet-sensitized photolysis with dissolved organic matter (DOM) in the aquatic environment. However, the mechanisms underlying the triplet-sensitized photolysis of SDZ with DOM have not been fully worked out. In this study, we investigated the mechanisms of triplet-sensitized photolysis of SDZ0 (neutral form) and SDZ− (anionic form) with four DOM analogues, i.e., fluorenone (FL), thioxanthone (TX), 2-acetonaphthone (2-AN), and 4-benzoylbenzoic acid (CBBP), and three metal ions (i.e., Mg2+, Ca2+, and Zn2+) effects using quantum chemical calculations. Results indicated that the triplet-sensitized photolysis mechanism of SDZ0 with FL, TX, and 2-AN was hydrogen transfer, and with CBBP was electron transfer along with proton transfer (for complex SDZ0-CBBP2) and hydrogen transfer (for complex SDZ0-CBBP1). The triplet-sensitized photolysis mechanisms of SDZ− with FL, TX, and CBBP was electron transfer along with proton transfer, and with 2-AN was hydrogen transfer. The triplet-sensitized photolysis product of both SDZ0 and SDZ− was a sulfur dioxide extrusion product (4-(2-iminopyrimidine-1(2H)-yl)aniline), but the formation routs of the products for SDZ0 and SDZ− were different. In addition, effects of the metal ions on the triplet-sensitized photolysis of SDZ0 and SDZ− were different. The metal ions promoted the triplet-sensitized photolysis of SDZ0, but inhibited the triplet-sensitized photolysis of SDZ−.