Allyl Sulfides Research Articles

A Versatile Comonomer Additive for Radically Recyclable Vinyl‐derived Polymers

AbstractRadically‐formed, vinyl‐derived polymers account for over 30 % of polymer production. Connected through stable carbon‐carbon bonds, these materials are notoriously challenging to chemically recycle. Herein, we report universal copolymerization of a cyclic allyl sulfide (CAS) additive with multiple monomers under free‐radical conditions, to introduce main‐chain dynamic motifs. Backbone allyl sulfides undergo post‐polymerization radical rearrangement via addition‐fragmentation‐transfer (AFT) that fosters both chain scission and extension. Scission is selectively induced through allyl sulfide exchange with small molecule thiyl radicals, resulting in oligomers as low as 14 % of the initial molar mass. Crucially, oligomers retain allyl sulfide end groups, enabling their extension with monomer under radical conditions. Extended, i.e., recycled, product molar mass is tunable through the ratio of monomer to oligomer, and can surpass that of the initial copolymer. Two scission‐extension cycles are demonstrated in copolymers with methyl methacrylate and styrene without escalation in dispersity. In illustration of forming higher‐value products, i.e., upcycling, we synthesized block copolymers through the extension of oligomers with a different vinyl monomer. Collectively, our approach to chemical recycling is unparalleled in its ability to 1) function in a variety of vinyl‐derived polymers, 2) complete radical closed‐loop cycling, and 3) upcycle waste material.

HS-SPME-GC-MS-based untargeted metabolomics reveals the enhancement of pungent flavor quality in soilless-cultivated Chinese chives by preharvest application of methyl jasmonate

To improve the pungent flavor quality of soilless cultivated Chinese chives (Allium tuberosum Rottler), the effect of foliar spraying with methyl jasmonate (MeJA) was studied. Electronic nose analysis showed that 500 μM MeJA significantly promoted the accumulation of aromatic compounds and organic sulfides in soilless-cultivated Chinese chives, as well as the content of pungent flavor metabolites, such as enzymatic pyruvic acid (24.9%–69.9%) and the garlic odor compounds alliin (22.1%–51.4%) and methionine (8.0%–62.7%). Using the HS-SPME-GC-MS technique, fifteen species of 186 volatile metabolites were detected in Chinese chive leaves treated with MeJA, and the sulfur compounds were dominating between them (49.6%–61.7%). Metabolomics and chemometrics analysis identified the volatile biomarkers of MeJA-treated substrate culture and hydroponic Chinese chives as dimethyl disulfide, dimethyl tetrasulfide, diallyl disulphide and allyl methyl sulfide, and methyl 2- propenyl disulfide, dimethyl tetrasulfide compound, respectively. Orthogonal partial least squares discriminant analysis indicated that MeJA treatment enhanced the pungency of Allium tuberosum mainly by increasing the accumulation of dimethyl sulfide and allyl sulfide compounds. Current study provides theoretical and technical basis for improving the pungent flavor quality of soilless-cultivated Chinese chives.

A Strategy for Controlling the Polymerizations of Thiyl Radical Propagation by RAFT Agents.

The ability to extend the polymerizations of thiyl radical propagation to be regulated by existing controlled methods would be highly desirable, yet remained very challenging to achieve because the thiyl radicals still cannot be reversibly controlled by these methods. In this article, we reported a novel strategy that could enable the radical ring-opening polymerization of macrocyclic allylic sulfides, wherein propagating specie is thiyl radical, to be controlled by reversible addition-fragmentation chain transfer (RAFT) agents. The key to the success of this strategy is the propagating thiyl radical can undergo desulfurization with isocyanide and generate a stabilized alkyl radical for reversible control. Systematic optimization of the reaction conditions allowed good control over the polymerization, leading to the formation of polymers with well-defined architectures, exemplified by the radical block copolymerization of macrocyclic allylic sulfides and vinyl monomers and the incorporation of sequence-defined segments into the polymer backbone. This work represents a significant step toward directly enabling the polymerizations of heteroatom-centered radical propagation to be regulated by existing reversible-deactivation radical polymerization techniques.

A Strategy for Controlling the Polymerizations of Thiyl Radical Propagation by RAFT Agents

AbstractThe ability to extend the polymerizations of thiyl radical propagation to be regulated by existing controlled methods would be highly desirable, yet remained very challenging to achieve because the thiyl radicals still cannot be reversibly controlled by these methods. In this article, we reported a novel strategy that could enable the radical ring‐opening polymerization of macrocyclic allylic sulfides, wherein propagating specie is thiyl radical, to be controlled by reversible addition–fragmentation chain transfer (RAFT) agents. The key to the success of this strategy is the propagating thiyl radical can undergo desulfurization with isocyanide and generate a stabilized alkyl radical for reversible control. Systematic optimization of the reaction conditions allowed good control over the polymerization, leading to the formation of polymers with well‐defined architectures, exemplified by the radical block copolymerization of macrocyclic allylic sulfides and vinyl monomers and the incorporation of sequence‐defined segments into the polymer backbone. This work represents a significant step toward directly enabling the polymerizations of heteroatom‐centered radical propagation to be regulated by existing reversible‐deactivation radical polymerization techniques.

Rapid Detection of Volatile Organic Metabolites in Urine by High-Pressure Photoionization Mass Spectrometry for Breast Cancer Screening: A Pilot Study.

Despite surpassing lung cancer as the most frequently diagnosed cancer, female breast cancer (BC) still lacks rapid detection methods for screening that can be implemented on a large scale in practical clinical settings. However, urine is a readily available biofluid obtained non-invasively and contains numerous volatile organic metabolites (VOMs) that offer valuable metabolic information concerning the onset and progression of diseases. In this work, a rapid method for analysis of VOMs in urine by using high-pressure photon ionization time-of-flight mass spectrometry (HPPI-TOFMS) coupled with dynamic purge injection. A simple pretreatment process of urine samples by adding acid and salt was employed for efficient VOM sampling, and the numbers of metabolites increased and the detection sensitivity was improved after the acid (HCl) and salt (NaCl) addition. The established mass spectrometry detection method was applied to analyze a set of training samples collected from a local hospital, including 24 breast cancer patients and 27 healthy controls. Statistical analysis techniques such as principal component analysis, partial least squares discriminant analysis, and the Mann-Whitney U test were used, and nine VOMs were identified as differential metabolites. Finally, acrolein, 2-pentanone, and methyl allyl sulfide were selected to build a metabolite combination model for distinguishing breast cancer patients from the healthy group, and the achieved sensitivity and specificity were 92.6% and 91.7%, respectively, according to the receiver operating characteristic curve analysis. The results demonstrate that this technology has potential to become a rapid screening tool for breast cancer, with significant room for further development.

Rh-Catalyzed [2,3]-Sigmatropic Rearrangement of Alkynyl Carbenes with Allyl Sulfides to Access Sulfide-Substituted 1,5-Enynes.

This study describes the development of Rh-catalyzed [2,3]-sigmatropic rearrangement of alkynyl carbenes with allyl sulfides. The protocol exhibits equitable functional group tolerance and allows the formation of a variety of synthetically valuable sulfide-substituted 1,5-enyne products. To the best of our knowledge, this is the first example of [2,3]-sigmatropic rearrangement of alkynyl carbenes. DFT analysis supports the involvement of rhodium carbene generation, sulfonium ylides formation, and [2,3]-sigmatropic rearrangement pathway.

Mitigating neophobia behaviour of Bandicota bengalensis in accepting poison bait and traps using sulphur compounds as additives

This study aimed to assess the potential of five different sulphur compounds, namely carbon disulphide, dimethyl sulphoxide, dimethyl sulphide, allyl sulphide, and dimethyl disulphide as bait additives in mitigating neophobia behaviour of Bandicota bengalensis towards poison bait and traps. The efficacy of different concentrations (5, 10, 20, 50, and 100 ppm) of each of the sulphur compounds in enhancing bait acceptance was evaluated by exposing them to rats in a laboratory setting. The results showed significantly higher acceptance of bait containing 5 ppm concentration of all the compounds. Moreover, exposure of bait mixed with 5 ppm of all the compounds under multi-choice condition in radial maze revealed higher consumption by female rats of bait admixed with carbon disulphide, while male rats consumed the baits containing carbon disulphide and dimethyl sulphide to a greater extent. Female rats showed significantly higher acceptance (76.22%) of 2% zinc phosphide bait admixed with 5 ppm of carbon disulphide while male rats showed significantly higher acceptance of 2% zinc phosphide bait admixed with carbon disulphide (70.83%) and dimethyl sulphide (60.28%). Field experiments showed that 2% zinc phosphide bait mixed with 50 ppm carbon disulphide significantly reduced rodent activity in wheat crop fields. In laboratory and semi-field conditions, carbon disulphide at a concentration of 5 ppm and, in crop fields, at a concentration of 50 ppm, increased the efficacy of multi-catch traps for B. bengalensis. The study suggests that using carbon disulphide can enhance poison bait acceptance and trapping, thereby mitigating neophobia behaviour and improving rodent control success.

Radical-Mediated Ring-Opening Photopolymerization for Semicrystalline Thermoplastic Additive Manufacturing

Conventional approaches to stereolithographic additive manufacturing (SLA) employ liquid resin formulations based on multifunctional (meth)acrylates and epoxides that afford cross-linked polymeric networks upon polymerization. Nevertheless, the utilization of resins that yield semicrystalline thermoplastics provides facile access to physical and mechanical properties that are otherwise difficult to attain, such as high toughness and resistance to solvent swelling as well as additional postfabrication processing options that can be used to extend the life cycle of three-dimensional printed polymers. Here, we report the SLA-based additive manufacturing of semicrystalline thermoplastics utilizing the radical-mediated ring-opening photopolymerization of seven- and eight-membered cyclic allylic sulfides. Photopolymerization of resin formulations incorporating seven- and eight-membered cyclic allylic sulfides and crystallization of the resultant (co)polymers were examined using Fourier transform infrared spectroscopy, photorheology, and isothermal photo-differential scanning calorimetry. The formulated resins were found to polymerize and subsequently crystallize rapidly upon irradiation under ambient conditions. The mechanical properties of stereolithographically printed copolymers approached the bulk copolymer mechanical properties, demonstrating unusually strong interlayer adhesion atypical of layerwise, stereolithographic printing of semicrystalline polymers. Finally, high-quality, recyclable, semicrystalline thermoplastic parts were printed and melted down, demonstrating the potential for these semicrystalline materials to provide a path for improved sustainability of polymeric parts produced via SLA.

Unexpectedly easy non-catalytic transfer of allyl group from allyl sulfides to secondary phosphine sulfides

The unexpected allylation of secondary phosphine sulfides with allyl sulfides has been found. The reaction proceeds under mild conditions (no catalyst and solvent, 80°C) to give allyldiorganylphosphine sulfides (yield up to 79%). The latter, under the reaction conditions, are able to add the initial secondary phosphine sulfides across the allyl group in the anti-Markovnikov mode to deliver propane-1,3-diylbis(diorganylphosphine sulfides), promising extractants of heavy metals and ligands for the synthesis of metal complex catalysts.

Embedding Peptides into Synthetic Polymers: Radical Ring-Opening Copolymerization of Cyclic Peptides.

Biopolymers such as proteins and nucleic acids are the key building blocks of life. Synthetic polymers have nevertheless revolutionized our everyday life through their robust synthetic accessibility. Combining the unmatched functionality of biopolymers with the robustness of tailorable synthetic polymers holds the promise to create materials that can be designed ad hoc for a wide array of applications. Radical polymerization is the most widely applied polymerization technique in both fundamental science and industrial polymer production. While this polymerization technique is robust and well controlled, it generally yields unfunctional all-carbon backbones. Combinations of natural polymers such as peptides, with synthetic polymers, are thus limited to tethering peptides onto the side chains or chain ends of the latter. This synthetic limitation is a critical restraint, considering that the function of biopolymers is programmed into the sequence of their main chain (i.e., primary structure). Here, we report the radical copolymerization of peptides and synthetic comonomers yielding synthetic polymers with defined peptide sequences embedded into their main chain. Key was the development of a solid-phase peptide synthesis (SPPS) approach to generate synthetic access to peptide conjugates containing allylic sulfides. Following cyclization, the obtained peptide monomers can be readily copolymerized with N,N-dimethylacrylamide (DMA)─controlled by reversible addition-fragmentation chain transfer (RAFT). Importantly, the developed synthetic strategy is compatible with all 20 standard amino acids and uses exclusively standard SPPS chemicals or chemicals accessible in one-step synthesis─prerequisite for widespread and universal application.

Unexpectedly Easy Noncatalytic Allyl Group Transfer from Allyl Sulfides to Secondary Phosphine Sulfides

Unexpectedly Easy Noncatalytic Allyl Group Transfer from Allyl Sulfides to Secondary Phosphine Sulfides

Organic-solvent-free oxidation of styrene, phenol and sulfides with H2O2 over eco-friendly niobium and tantalum based heterogeneous catalysts

Immobilization of triperoxido derivatives of Nb(V) and Ta(V) on chitosan, an abundant and renewable support material, afforded a pair of stable heterogeneous catalysts, which could be successfully implemented in a variety of organic oxidations under ecologically sustainable organic-solvent-free conditions. The catalysts were extensively characterized by elemental analysis, SEM-EDX, powder XRD, XPS, BET, TG-DTG, FT-IR, Raman and NMR analysis. The supported catalysts showed excellent activity in the non-solvent epoxidation of styrene with H2O2 to provide 96% conversion with nearly 100% selectivity of the desired epoxide and a high TON value of 260 at room temperature. Moreover, phenol was selectively converted into 100% dihydroxybenzene (HQ:CT = 2:1) at ambient temperature, in absence of organic solvent, with a TON value of 80. In addition, both the catalysts were highly active towards the oxidation of a diverse range of sulfides such as aromatic, aliphatic, vinylic, allylic, and alcoholic sulfides to chemoselectively produce the desired sulfoxides in an aqueous medium with a TON value as high as 1900. The heterogeneous nature of the insoluble catalysts was confirmed by a hot filtration test. The catalysts are stable, water tolerant and easily recyclable at least up to five successive cycles of epoxidation and sulfoxidation with undiminished activity and selectivity.

Free-radical photoring-opening polymerization of cyclic allylic sulfide: From photocleavable photoinitiators to three components photoredox systems

Photopolymers form a family of materials that have been developed to meet specific demands in fields such as coatings, varnishes, semiconductors, optical fibers, printing plates, holographic recording, etc. However, the multifunctional acrylate monomers currently used present an important volume contraction. A drawback for applications where little shrinkage during polymerization is mandatory to keep shapes and properties of the material. To overcome this problem, monomers reacting by ring opening polymerization can be used. Among possible monomers, cyclic allylic sulfides are very interesting candidates: they are highly reactive and their polymerization mechanism is almost not affected by the presence of oxygen. In this work the effects of the photoinitiating systems on the free radical ring opening photopolymerization kinetics of an eight-member cyclic allylic sulfide is studied. It is shown that cleavable type I, bimolecular type II and three components redox photoinitiating systems allow the formation of linear photopolymers with high polymerization rates and final conversions. The photopolymerization kinetics obtained show that the photopolymerization is not sensitive to oxygen which leads to reduced exposure time and higher sensitivity. This remarkable property should also extend the usage of such monomers in the coating applications where oxygen inhibition is a drawback. Finally, the benefit of ring opening polymerization process is demonstrated trough the volume contraction measurement which was found to be lower than 1.5%.

Programming Photodegradability into Vinylic Polymers via Radical Ring‐Opening Polymerization

AbstractIncorporation of photolabile moieties into the polymer backbone holds promise to remotely‐control polymer degradation. However, suitable synthetic avenues are limited, especially for radical polymerizations. Here we report a strategy to program photodegradability into vinylic polymers by exploiting the wavelength selectivity of photocycloadditions for radical ring‐opening polymerization (rROP). Irradiation of coumarin terminated allylic sulfides with UVA light initiated intramolecular [2+2] photocycloaddition producing cyclic macromonomers. Subsequent RAFT‐mediated rROP with methyl acrylate yielded copolymers that inherited the photoreactivity of the cyclic parent monomer. Irradiation with UVB initiated efficient photocycloreversion of the coumarin dimers, causing polymer degradation within minutes under UVB light or days under sunlight exposure. Our synthetic strategy may pave the way to insert photolabile linkages into vinylic polymers, tuning degradation for specific wavelengths.

Programming Photodegradability into Vinylic Polymers via Radical Ring-Opening Polymerization.

Incorporation of photolabile moieties into the polymer backbone holds promise to remotely-control polymer degradation. However, suitable synthetic avenues are limited, especially for radical polymerizations. Here we report a strategy to program photodegradability into vinylic polymers by exploiting the wavelength selectivity of photocycloadditions for radical ring-opening polymerization (rROP). Irradiation of coumarin terminated allylic sulfides with UVA light initiated intramolecular [2+2] photocycloaddition producing cyclic macromonomers. Subsequent RAFT-mediated rROP with methyl acrylate yielded copolymers that inherited the photoreactivity of the cyclic parent monomer. Irradiation with UVB initiated efficient photocycloreversion of the coumarin dimers, causing polymer degradation within minutes under UVB light or days under sunlight exposure. Our synthetic strategy may pave the way to insert photolabile linkages into vinylic polymers, tuning degradation for specific wavelengths.

Allyl sulfides in garlic oil initiate the formation of renewable adhesives

Garlic essential oil (GEO) was used as the monomer, solvent and initiator to form adhesives. Analysis of GEO and the resulting polysulfide properties improved our understanding of poly(GEO) providing a route to develop renewable, S-based materials.

Microwave- and Thermally Promoted Iminyl Radical Cyclizations: A Versatile Method for the Synthesis of Functionalized Pyrrolines.

A detailed study of iminyl radical cyclizations of O-aryloximes tethered to alkenes is reported. The reactions can be triggered by either microwave irradiation or conventional heating in an oil bath. A variety of radical traps can be employed, enabling C-C, C-N, C-O, C-S, or C-X bond formation and producing a diverse array of functionalized pyrrolines. Substrates containing an allylic sulfide furnish terminal alkenes by a tandem cyclization-thiyl radical β-elimination pathway. Cyclizations of hydroxylated substrates exhibit moderate diastereoselectivity that in some cases can partially be attributed to intramolecular hydrogen bonding. Computational studies suggested a possible role for thermodynamics in controlling the stereochemistry of cyclizations. The reaction temperature can be lowered from 120 to 100 °C by employing O-(p-tert-butylphenyl)oximes instead of O-phenyloximes as substrates, and these second-generation iminyl radical precursors can be used in a one-pot oxime ether formation-cyclization that is promoted by conventional heating. The functionalized pyrrolines obtained from these reactions can be conveniently transformed in several different ways.

Evaluation of allyl sulfides bearing methacrylate groups as addition-fragmentation chain transfer agents for low shrinkage dental composites

Polymerization shrinkage and the consequential shrinkage stress in methacrylate-based dental composites are crucial drawbacks for restorative dentistry. An effective way for the reduction of shrinkage stress is the incorporation of addition fragmentation chain transfer agents (AFCT agents). In this contribution, four novel polymerizable allyl sulfides were synthesized and evaluated in dental composites. Photo-DSC and DMTA measurements were performed to evaluate their influence on the polymerization rate and on the network homogeneity. Good to excellent shrinkage force values and mechanical properties were obtained for all AFCT based composites. Especially, the incorporation of AFCT agents containing multiple urethane and methacrylate moieties improved the mechanical properties. Hence, the incorporation of polymerizable and urethane-based allyl sulfides in dental composite is a promising strategy to obtain low shrinkage materials exhibiting high flexural strength and modulus.

HFIP-Induced Allylation Reaction of Tertiary Allylic Alcohols with Thiols or Sulfonyl Hydrazines to Access Allylic Organosulfurs

AbstractA simple and transition-metal-free HFIP-induced allylation reaction of tertiary allylic alcohols with thiols or sulfonyl hydrazine derivatives was reported for the efficient and highly selective synthesis of allylic sulfides and allylic sulfones. Herein, HFIP played a vital role in not only activating the allylic alcohol, but also stabilizing the allylic cation intermediate to accelerate the subsequent transformations.

Isolation and Analysis of Chemical Components of Garlic (Allium sativum L.) Tuber Essential Oil As Well As Antibacterial and Antioxidant Activity Tests

The essential oil from garlic tubers (Allium sativum L) was isolated by hydrodistillation method using the Stahl apparatus. Garlic tubers were distilled for 4 to 5 hours to produce as much oil as 0.05% (w/ w). The chemical components of essential oil of garlic tubers were analyzed using GC-MS spectroscopy. The GC-MS results showed that there were 11 components with 5 main components, namely diallyl disulfide (44.98%), 1,3-diallyl tri sulfane (13.63%), allyl sulfide (13.06%), methyl allyl disulfide (11.87%), and methyl allyl trisulfide (4.84%). The antibacterial activity of essential oil of garlic tubers with diffusion method to use concentration variation of 5%, 10%, and 15% have strong antibacterial activity against Gram-positive bacteria like Staphylococcus aureus and have a medium to strong antibacterial activity against Gram-negative bacteria like Escherichia coli. The antioxidant activity of the essential oil of garlic tubers with DPPH (2,2-diphenyl-1-picrylhydrazil) showed an IC50 value was 22.863 mg/L and a very strong antioxidant group.