Unsaturated Carbon-carbon Bonds Research Articles

Silver-Catalyzed 1,2-Thiosulfonylation of Alkenes: Development of a Nucleophilic d3-Methylthiolating Reagent.

Development of robust d3-methylthiolating reagents represents an attractive synthetic method to access deuterated molecules in the field of drug discovery. Here, we report a straightforward strategy to prepare electrophilic S-methyl-d3 arylsulfonothioates in one-step without column purification. These reagents exhibit good radical reactivity toward silver-catalyzed vicinal thiosulfonylation of alkenes or 1,6-enynes on water. As a result, simultaneous incorporation of both SCD3 and ArSO2 units into unsaturated carbon-carbon bonds with 100% atom economy has been established. Moreover, the ATRA adducts with >99% D incorporation can serve as nucleophilic d3-methylthiolating synthons via retro-Michael addition under mild basic conditions, providing a good alternative in trideuteromethylthiolating alkyl iodides to access corresponding trideuteromethyl sulfides with high efficiency.

Precise Pore Engineering of Zirconium Metal-Organic Cages for One-Step Ethylene Purification from Ternary Mixtures.

One-step purification of ethylene from ternary mixtures (C2H2, C2H4, and C2H6) can greatly reduce the energy consumption of the separation process, but it is extremely challenging. Herein, we use crystal engineering and reticular chemistry to introduce unsaturated bonds (ethynyl and alkyne) into ligands, and successfully design and synthesized two novel Zr-MOCs (ZrT-1-ethenyl and ZrT-1-alkyne). The introduction of carbon-carbon unsaturated bonds provides abundant adsorption sites within the framework while modulating the pore window size. Comprehensive characterization techniques including single crystal and powder X-ray diffraction, as well as electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) confirm that ZrT-1-ethenyl and ZrT-1-alkyne possess an isostructural framework with ZrT-1 and ZrT-1-Me, respectively. Adsorption isotherms and breakthrough experiments combined with theoretical calculations demonstrate that ZrT-1-ethenyl can effectively remove trace C2H2 and C2H6 in C2H4 and achieve separation of C2H2 from C2H4 and CO2. ZrT-1-ethenyl can also directly purify C2H4 in liquid solutions. This work provides a benchmark for MOCs that one-step purification of ethylene from ternary mixtures.

Ambient hydrogenation of solid aromatics enabled by a high entropy alloy nanocatalyst

Hydrogenation is a versatile chemical process with significant applications in various industries, including food production, petrochemical refining, pharmaceuticals, and hydrogen carriers/safety. Traditional hydrogenation of aromatics, hindered by the stable π-conjugated phenyl ring structures, typically requires high temperatures and pressures, making ambient hydrogenation a grand challenge. Herein, we introduce a PdPtRuCuNi high entropy alloy (HEA) nanocatalyst, achieving an exceptional 100% hydrogenation of carbon-carbon unsaturated bonds, including alkynyl and phenyl groups, in solid 1,4-bis(phenylethynyl)benzene (DEB) at 25 °C under ≤1 bar H2 and solventless condition. This results in a threefold higher hydrogen uptake for DEB-contained composites compared to conventional Pd catalysts, which can only hydrogenate the alkynyl groups with a ~ 27% conversion of DEB. Our experimental results, complemented by theoretical calculations, reveal that PdPtRu alloy is highly active and crucial in enabling the hydrogenation of phenyl groups, while all five elements work synergistically to regulate the reaction rate. Remarkably, this newly developed catalyst also achieves nearly 100% reactivity for ambient hydrogenation of a broad range of aromatics, suggesting its universal effectiveness. Our research uncovers a novel material platform and catalyst design principle for efficient and general hydrogenation. The multi-element synergy in HEA also promises unique catalytic behaviors beyond hydrogenation applications.

A discovery for phosphorus valence and unsaturated bonds in polyphosphate/polyphosphonate: Promotion or inhibition for its flame-retardant mode of action in PET

Four polyphosphate/polyphosphonate flame retardants (PAP, POP, PAP-UB and POP-UB) have been designed and synthesized to study the effects of phosphorus valence states and the presence of unsaturated carbon-carbon double bonds on self-cross-linking impacting flame-retardant modes of action. It was found that phosphorus valence states affect the proportion of flame-retardant activity between the gas phase and condensed phase. A phosphonate containing +3-valence phosphorus is primarily effective as a gas-phase flame-retardant, while the one containing +5-valence phosphorus mainly exerted an impact in the condensed phase. The introduction of an unsaturated bond enhances the carbon-forming effect promoted by polyphosphates/polyphosphonates in a degrading polymer matrix and increases the melt viscosity for blends at high temperature. The phosphorus-containing fragments which might have been released into the gas phase are locked in the condensed phase due to CC bonds cross-linking, thus forming more high-quality phosphorus-rich char layers. This effect balances the distribution of gas-phase and condense-phase flame-retardant effects and is especially obvious in PET/polyphosphonate blends containing +3-valence phosphorus, which originally plays mainly the role of a gas-phase flame retardant. PET blends containing unsaturated carbon-carbon double bonds display better carbon formation, flame-retardant activity and anti-dripping behavior than these do without this feature.

Synthetic Utilization of 2H-Heptafluoropropane: Ionic 1,4-Addition to Electron-Deficient Carbon-Carbon Unsaturated Bonds.

We have found a novel method for introducing heptafluoro-2-propyl CF(CF3)2 groups into carbon-carbon unsaturated bonds via a nucleophilic reaction using 2H-heptafluoropropane as the source of CF(CF3)2 groups. The reaction involves the nucleophilic addition of a heptafluoro-2-propyl anion, generated by treating 2H-heptafluoropropane with a fluoride ion, to various electron-deficient unsaturated compounds. This allows the easy synthesis of various aliphatic compounds containing heptafluoro-2-propyl groups.

Applications of Nucleophilic Fluorine Sources in the Selective Fluorofunctionalization of Unsaturated Carbon-Carbon Bonds

Applications of Nucleophilic Fluorine Sources in the Selective Fluorofunctionalization of Unsaturated Carbon-Carbon Bonds

Transition-Metal-Catalyzed Addition of Organosulfur Compounds to Alkynes and Alkenes: Catalysis and Catalyst Poisons.

The addition of heteroatom compounds to alkynes and alkenes is an atom-efficient method of carbon-heteroatom bond formation and is widely used as a fundamental synthetic method for the construction of functional molecules. Nevertheless, examples of transition-metal-catalyzed addition reactions of group 16 heteroatom compounds to carbon-carbon unsaturated bonds have been limited due to the widespread belief that organic sulfur and selenium compounds are representative catalyst poisons. In recent decades, however, several seminal catalytic reactions of sulfur compounds have been developed, providing important insights into catalysis and poisons. Therefore, in this paper, we focus on the transition-metal-catalyzed addition of organosulfur compounds to alkynes and alkenes, gain comprehensive insights into the catalysis and catalyst poisons, and propose concepts for the development of transition-metal-catalyzed reactions of group 16 heteroatom compounds.

(Digital Presentation) Renewable Itaconic Acid As a Cathode Additive Stabilizing Ni-Rich Layered Cathode Materials for Lithium-Ion Batteries

Renewable materials applied in lithium-ion batteries industry has obvious advantages because of its wide range of sources and low cost. The residual lithium compounds on the surface of nickel-rich LiNi1-x-yCoxMnyO2 (Ni-rich NCM) cathodes hinder its large-scale industrial application in lithium-ion batteries. In the past, researchers proposed several approaches including coating (Al2O3, Li3PO4), water washing coupling heat treatment. These conventional approaches have been found beneficial for mitigating the residual lithium and improving electrochemical performance of high rich nickel cathode. However, most of these used conventional additions are non-renewable precious metal or salt accompanied by extra processing/handling costs. More seriously, layer Ni-rich NCM cathodes cost more than lithium iron phosphate, because transition nickel salt is expensive. Obviously, it is crucial for Ni-rich NCM cathodes to develop green and low-cost modification process.In this work, renewable itaconic acid (IA) as a cathode addition is used to convert the residual lithium on the Ni-rich NCM cathodes into sacrificial organic lithium salts containing polar carboxylic acid and unsaturated carbon-carbon double bond to build the Li conductive cathode-electrolyte interphase (CEI) rich in organic component containing polycarbonates/polymeric specie during the electrochemical process. As a result, the capacity of the 0.5wt% IA modified NCM cathode retains 94.1 % after 90 cycles. Itaconic anhydride, an important renewable resource, is widely used in food processing and other fields because of its wide range of sources and low price. As such, our work proposes a practical approach to mitigates residual lithium issue and control CEI formation, developing high energy and long spans lithium-ion batteries by utilizing cheap and renewable organic acid. Figure 1

Hydride-Free Hydrogenation: Unraveling the Mechanism of Electrocatalytic Alkyne Semihydrogenation by Nickel-Bipyridine Complexes.

Hydrogenation reactions of carbon-carbon unsaturated bonds are central in synthetic chemistry. Efficient catalysis of these reactions classically recourses to heterogeneous or homogeneous transition-metal species. Whether thermal or electrochemical, C-C multiple bond catalytic hydrogenations commonly involve metal hydrides as key intermediates. Here, we report that the electrocatalytic alkyne semihydrogenation by molecular Ni bipyridine complexes proceeds without the mediation of a hydride intermediate. Through a combined experimental and theoretical investigation, we disclose a mechanism that primarily involves a nickelacyclopropene resting state upon alkyne binding to a low-valent Ni(0) species. A following sequence of protonation and electron transfer steps via Ni(II) and Ni(I) vinyl intermediates then leads to olefin release in an overall ECEC-type pattern as the most favored pathway. Our results also evidence that pathways involving hydride intermediates are strongly disfavored, which in turn promotes high semihydrogenation selectivity by avoiding competing hydrogen evolution. While bypassing catalytically competent hydrides, this type of mechanism still retains inner-metal-sphere characteristics with the formation of organometallic intermediates, often essential to control regio- or stereoselectivity. We think that this approach to electrocatalytic reductions of unsaturated organic groups can open new paradigms for hydrogenation or hydroelementation reactions.

Small change, big impact: Simply changing the substitute on Si atom towards significant improvement of flame retardancy and toughness of epoxy resins

Enhancing simultaneously the flame retardancy and mechanical properties of polymer materials is a good expectation but always a tough challenge. In this work, two multifunctional compounds: phosphaphenanthrene/vinylsiloxane (DDVS) and phosphaphenanthrene/phenylsiloxane (DDPS) were synthesized, and both effectively improved the flame-retardant properties, toughness and UV shielding performance of epoxy resins (EPs) with high transparency. It was further found that the flame retardancy and toughness of EPs were greatly affected by simply changing the substituents from phenyl to vinyl groups on Si atom. Compared with DDPS, DDVS with vinyl group on Si showed more efficiency in improving flame retardancy (higher LOI value), self-extinguishing properties (higher UL 94 grade) and higher quality retention (more carbon residue) in EP. For example, DDVS was added in two-thirds of the amount of DDPS to make EPs achieve UL94 V-0 rating. This attributed to the high-temperature self-crosslinking of unsaturated carbon-carbon double bonds in DDVS, which can increase the charring ability of EPs and form more high-temperature stable char residues. Meantime, this also inhibited the release of volatile phosphorus-containing pieces from DDVS decomposition and retained more P in condense phase, thus improving the compactness and graphitization degree of char layers. The introduction of unsaturated bonds strengthened the condense-phase flame-retardant function of DDVS in EP, while retaining the original gas-phase flame-retardant actions of DOPO groups. The mechanism of gas-phase and condensed-phase mechanisms cooperated with each other, obtaining better flame retardant effect. Meanwhile, DDVS possessed greater efficiency than DDPS in increasing the fracture toughness of matrix due to the difference of steric hindrance between the substituents on silicon. Furthermore, the introduction of DDVS and DDPS did not significantly affect the transparency of EPs and the high visual transparency of materials was still maintained. In brief, the coordination design of phosphaphenanthrene and vinylsiloxane groups provided a theoretical basis to simultaneously improve the flame retardancy and toughening of EPs without losing glass transition temperature, while maintaining the high visual transparency of EPs with good UV shielding performance.

A novel colorimetric and red-emitting fluorescent probe based on benzopyrylium derivatives for selective detection and imaging of SO2 derivatives in cells and zebrafish

Abnormal levels of endogenous sulfur dioxide in organisms will cause cardiovascular, respiratory and neurological diseases. Therefore, the development of an effective detecting method for real-time, quantitative detection of sulfur dioxide derivatives in organisms is of great importance in physiological and pathological aspects. In this work, a red-emitting SO2 fluorescent probe based on benzopyrylium derivatives were designed and synthesized to specifically detect SO2 derivatives by nucleophilic addition of unsaturated carbon-carbon double bonds. The probe is characterized with rapid response, “naked eye” visualization, broad detection range and high sensitivity (8.1 μM) for SO2 derivatives. In addition, it has been applied to track the dynamic, real-time, visual detection of exogenous and endogenous SO2 in cells, and imaging of exogenous SO2 derivatives in zebrafish.

Iodine-Oxidized Diene-Based Rubbers as Anti-icing and Deicing Polymer Coatings.

In an effort to prevent or minimize icing hazards, techniques and materials for icing inhibition and deicing have always been highly favored throughout human history. This work discovers the integrated anti-icing and deicing effects of poly(styrene-b-butadiene-b-styrene) triblock rubber (SBS) after its easy oxidation in iodine vapor. Iodine oxidation happens on the block of polybutadiene, featured by the conversion of SBS from hydrophobic to amphiphilic and the improved capability of photothermal conversion. The oxidized SBS can serve as a polymer coating, which possesses intriguing abilities to delay the kinetics of icing on its surface and repel the ice under light illumination. According to characterizations of surface chemistry and mechanical performance, iodine oxidation is assumed to involve the processes of iodine coordination to unsaturated bonds, the formation of radical cations as a result of the redox reaction between iodine and unsaturated carbon-carbon bonds, improved light absorption owing to the formation of polyiodide anions, and intermolecular coupling of radical cations. The appearance of polar moieties/species within the oxidized SBS is attributed to the delayed ice nucleation. The significant photothermal capacity in visible and near-infrared windows enables the iodine-oxidized SBS coating to remove the adhered ice by melting under light illumination when the icing process is inevitable, even at an extremely low temperature (-25 °C).

Pd(II)-Catalyzed Aminoacetoxylation of Alkenes Via Tether Formation.

A Pd-catalyzed method based on the use of a molecular tether is described for olefin difunctionalization. Enabled by an easily introduced trifluoroacetaldehyde-derived tether, a simultaneous introduction of oxygen and nitrogen heteroatoms across unsaturated carbon–carbon bonds was achieved under oxidative conditions, most probably via high-valent Pd intermediates. Good yields and high diastereoselectivity were obtained with aryl-substituted alkenes, whereas nonterminal alkyl-substituted olefins gave aza-Heck products. Tether cleavage under mild conditions provided fast access to functionalized β-amino alcohols.

S-Block Metal Catalysts for the Hydroboration of Unsaturated Bonds.

The addition of a B–H bond to an unsaturated bond (polarized or unpolarized) is a powerful and atom-economic tool for the synthesis of organoboranes. In recent years, s-block organometallics have appeared as alternative catalysts to transition-metal complexes, which traditionally catalyze the hydroboration of unsaturated bonds. Because of the recent and rapid development in the field of hydroboration of unsaturated bonds catalyzed by alkali (Li, Na, K) and alkaline earth (Mg, Ca, Sr, Ba) metals, we provide a detailed and updated comprehensive review that covers the synthesis, reactivity, and application of s-block metal catalysts in the hydroboration of polarized as well as unsaturated carbon–carbon bonds. Moreover, we describe the main reaction mechanisms, providing valuable insight into the reactivity of the s-block metal catalysts. Finally, we compare these s-block metal complexes with other redox-neutral catalytic systems based on p-block metals including aluminum complexes and f-block metal complexes of lanthanides and early actinides. In this review, we aim to provide a comprehensive, authoritative, and critical assessment of the state of the art within this highly interesting research area.

Photoinduced Bisphosphination of Alkynes with Phosphorus Interelement Compounds and Its Application to Double-Bond Isomerization.

The addition of interelement compounds with heteroatom-heteroatom single bonds to carbon-carbon unsaturated bonds under light irradiation is believed to be an atomically efficient method to procure materials with carbon-heteroatom bonds. In this study, we achieved the photoinduced bisphosphination of alkynes using the phosphorus interelement compound, tetraphenyldiphosphine monosulfide (1), to stereoselectively obtain the corresponding (E)-vic-1,2-bisphosphinoalkenes, which are important transition-metal ligands. The bisphosphination reaction was performed by mixing 1 and various alkynes and then exposing the mixture to light irradiation. Optimization of the conditions for the bisphosphination reaction resulted in a wide substrate range and excellent trans-selectivity. Moreover, the completely regioselective introduction of pentavalent and trivalent phosphorus groups to the terminal and internal positions of the alkynes, respectively, was achieved. We also found that the novel double-bond isomerization reaction of the synthesized bisphosphinated products occurred with a catalytic amount of a base under mild conditions. Our method for the photoinduced bisphosphination of carbon-carbon unsaturated compounds may have strong implications for both organic synthesis and organometallic and catalyst chemistry.

Gold(I)-catalyzed divergent and diastereoselective synthesis of azepines by ammoniumation/ring-expansion reactions

Gold(I) catalysts enable the chemoselective addition of tailor-made N-sulfonylated azetidine derivatives onto alkynes, affording bicyclic vinyl-ammonium gold intermediates. Intramolecularly intercepted by an adequately positioned nucleophilic carbonate or ester function, these ammoniums efficiently lead to ring-expanded azepine products, which are important pharmacophore fragments. Depending on the substitution pattern of the starting material, divergent deauration pathways occur, stereoselectively producing monomeric or original dimeric nitrogenated seven-membered rings in good to excellent yields, such as cis -tetrahydroazepin-4,5-diol carbonate, ( E )-alkylidene tetrahydroazepin-4-yl ester, and cis -bis(azepinyl)cyclobutane derivatives. One of the synthetic methods was extended to the formation of dihydrobenzazepines of high pharmaceutical value. A mechanistic study including kinetics and labeling experiments allowed us to fully understand the origin of the high chemo- and diastereoselectivity of these rearrangements. Overall, this work demonstrates the underlying synthetic potential of the ammoniumation catalyzed by gold for the future development of reaction cascades and preparation of bioactive compounds. • Gold-catalyzed ammoniumation of alkynes gives biologically relevant azepines • Functional groups on the starting material define the mechanistic pathway • NMR labeling and kinetic studies explain the chemo- and stereoselectivities observed • A dimeric bis(azepinyl)cyclobutane original scaffold is reported In the family of nitrogen heterocyclic drugs, azepine and its derivatives are very important pharmacophore fragments present in several pharmaceutical and a few agrochemical products. Currently, synthetic access to (hydro)azepine systems starting from simple and robust building blocks remains challenging, especially when targeting densely functionalized motifs. From tailor-made azetidine derivatives, we developed three diastereoselective methods to reach azepines with broad flexibility in good to excellent yields by using the unmatched ability of gold, a quasi-nontoxic metal, to promote nucleophilic additions onto unsaturated carbon-carbon bonds. The work described herein could offer efficient and modular routes to the preparation of useful intermediates in drug development. Azepines are fragments found in natural products possessing relevant biological activities. Our method provides access to multiple azepine derivatives from simple azetidine derivatives in the presence of a gold catalyst. Small variations on the starting material conduct to different reaction cascades whose mechanisms have been thoroughly studied to explain and control the observed selectivity. This journey led to the discovery of original azepine scaffolds along the way, whose biological activity remains to be studied.

Multifunctional organosilicon compound contributes to stable operation of high-voltage lithium metal batteries

With the increasing demand for high-energy–density energy storage devices, lithium metal batteries have rekindled the interest of researchers due to ultra-high specific capacity. However, the extremely unstable interfaces between the electrolyte and electrodes limit its application seriously. Herein, we introduce an organosilicon compound, 1,3-Divinyltetramethyldisiloxane (DTMDS), as multifunctional electrolyte additive to enhance the performance of LiNi0.5Mn1.5O4/Li batteries. DTMDS contains two functional groups: siloxane groups (Si-O) and unsaturated carbon-carbon double bonds (CC). Siloxane groups can capture hydrogen fluoride (HF) in electrolyte, and the carbon-carbon double bonds can form thin and dense passivation layer on both cathode and anode surfaces by polymerization. As a result, the capacity retention of the batteries can retain more than 95% after 500 cycles. This work provides a valuable reference for the design of multifunctional additives and stabilizing the interfaces of high-voltage lithium metal batteries.

Computational study on atom-economic alkyne hydrotelluration reaction using benchmarked ECP for Te

Geometry and energy calibration studies are done for arriving at a proper ECP for tellurium containing compounds. Among the various d-function included ECPs cc-pwCVTZ-PP and def2-TZVP give more reliable results. Non-catalytic and base/radical initiated hydrotelluration reactions are computationally studied using the calibrated def2-TZVP, with a special focus on the regio-and stereoselective formation of vinyl tellurides. The explored gas phase reaction mechanism indicates the addition of tellurol to unsaturated carbon-carbon triple bond via a concerted transition structure. Regioselectivity has been noticeably realized in presence of both base and radical mediated hydrotelluration leading to Markovnikov and anti-Markovnikov product respectively.

Stereospecific Si-C coupling and remote control of axial chirality by enantioselective palladium-catalyzed hydrosilylation of maleimides

Hydrosilylation of unsaturated carbon-carbon bonds with hydrosilanes is a very important process to access organosilicon compounds and ranks as one of the most fundamental reactions in organic chemistry. However, catalytic asymmetric hydrosilylation of activated alkenes and internal alkenes has proven elusive, due to competing reduction of carbon-carbon double bond or isomerization processes. Herein, we report a highly enantioselective Si-C coupling by hydrosilylation of carbonyl-activated alkenes using a palladium catalyst with a chiral TADDOL-derived phosphoramidite ligand, which inhibits O-hydrosilylation/olefin reduction. The stereospecific Si-C coupling/hydrosilylation of maleimides affords a series of silyl succinimides with up to 99% yield, >99:1 diastereoselectivity and >99:1 enantioselectivity. The high degree of stereoselectivity exerts remote control of axial chirality, leading to functionalized, axially chiral succinimides which are versatile building blocks. The product utility is highlighted by the enantioselective construction of N-heterocycles bearing up to three stereocenters.

Atomic Pt-Catalyzed Heterogeneous Anti-Markovnikov C-N Formation: Pt10 Activating N-H for Pt1δ+-Activated C═C Attack.

C-N formation is of great significance to synthetic chemistry, as N-containing products are widely used in chemistry, medicine, and biology. Addition of an amine to an unsaturated carbon-carbon bond is a simple yet effective route to produce new C-N bonds. But how to effectively conduct an anti-Markovnikov addition with high selectivity has been a great challenge. Here, we proposed a strategy for highly regioselective C-N addition via hydroamination by using supported Pt. It has been identified that atomic-scale Pt is the active site for C-N addition with Pt12+ for Markovnikov C-N formation and atomic Pt (Pt1δ+ and Pt10) contributing to anti-Markovnikov C-N formation. A selectivity of up to 92% to the anti-Markovnikov product has been achieved with atomic Pt in the addition of styrene and pyrrolidine. A cooperating catalysis for the anti-Markovnikov C-N formation between Pt1δ+ and Pt10 has been revealed. The reaction mechanism has been studied by EPR spectra and in situ FT-IR spectra of adsorption/desorption of styrene and/or pyrrolidine. It has been demonstrated that Pt10 activates amine to be electrophilic, while Pt1δ+ activates C═C by π-bonding to make β-C nucleophilic. The attack of nucleophilic β-C to electrophilic amine affords the anti-Markovnikov addition. This strategy proves highly effective to a variety of substrates in anti-Markovnikov C-N formation, including aromatic/aliphatic amines reacting with aromatic olefins, aromatic/aliphatic olefins with aromatic amines, and linear aliphatic olefins with secondary aliphatic amines. It is believed that the results provide evidence for the function of varied chemical states in monatomic catalysis.