Migration Reaction Research Articles

Design and Synthesis of Dialkylarylphosphine Urea Ligands and their Application in Palladium‐Catalyzed Cross‐Coupling Reactions

AbstractWe describe herein the design and synthesis of a new class of dialkylarylphosphine ligands incorporating a Lewis‐basic urea subunit. The ligand synthesis consisted of six linear steps and was enabled by the discovery of a new N‐to‐N alkyl migration reaction. This new series of dialkylarylphosphine urea ligands were applied in common palladium‐catalyzed cross‐coupling reactions for the formation of carbon‐carbon and carbon‐nitrogen bonds in moderate to high yields.

Gas-phase F-atom migration reaction of deprotonated N-fluoroarenesulfonamides.

Recently N-Fluoroarenesulfonamides (ArSO2 NHF) were found to be promising precursors for the preparation of N-fluorobenzenesulfonimide derivatives without applying F2 . However, very few studies have discussed the mass spectrometric behaviors of ArSO2 NHF with N-F structure. In this article, we applied high-resolution electrospray ionization tandem mass spectrometry (HR-ESI-MS/MS) to study the effect on the mass spectrometric behaviors of ArSO2 NHF after the introduction of the F-atom to the N-atom of ArSO2 NH2 . High-resolution electrospray ionization mass spectrometry (HR-ESI-MS) experiments showed that ArSO2 NHF produced only good signals in negative ion mode, and the dominating product ion SO2 F- at m/z 83 was observed in all HR-ESI-MS/MS of ArSO2 NF- with different substituents in the Ar group. The formation of the product ion SO2 F- was proof of the gas-phase F-atom migration rearrangement from the N-atom to the S-atom in ESI-MS/MS of ArSO2 NF- . To fully explain the gas-phase reaction mechanism from ArSO2 NF- to SO2 F- , we studied the HR-ESI-MS/MS of deprotonated ArSO2 NHF and also performed theoretical calculations. Both results confirmed that ArSO2 NF- first underwent Smiles rearrangement to yield intermediate I (INT1) ArNFSO2 - , and then the F-atom of ArNFSO2 - migrated from the N-atom to the S-atom to form intermediate II (INT2) ArN- SO2 F, which finally dissociated to SO2 F- at m/z 83 with loss of a neutral nitrene (ArN). All these results showed that the formation of the product ion SO2 F- from ArSO2 NF- was a common and intrinsic gas-phase reactivity of ArSO2 NF- .

Unravelling the Factors Influencing Halide Perovskite Based Switchable Photovoltaics

AbstractLead halide perovskites have revolutionized the field of optoelectronics (such as photovoltaics and light emitting diodes) demonstrating extraordinary material properties despite being formed at low temperatures. However, ion migration in the bulk or at the interfaces results in stability issues especially in devices where metal electrodes directly interface with the perovskite film. Utilizing the switchable photovoltaic phenomenon (SPV) in halide perovskites as a measure of ion migration and electrochemical reactions within them, Cs0.05MA0.15FA0.70PbI2.5Br0.5 triple cation perovskite, widely used in photovoltaics is evaluated. The various factors determining the SPV, including electric field magnitudes, type of metal contacts, Illumination conditions, and temperature is systematically measured. This study reveals the roles of electrode work functions and reactivities on ion migration and local electronic structure modulation. ITO electrodes demonstrated the highest open‐circuit voltage (Voc) about 0.85 V while Ag electrodes developed conductive filaments. However, the Voc distribution for Ti and Cr electrodes shows a more pronounced linear correlation with the poling electric field strength. Insights from this lateral design are directly relevant to transistor and memristor architectures and offer inputs into the design of perovskite‐based photovoltaic/optoelectronic devices.

SnS2 nanosheets/Ag2S quantum dots heterojunction supported by YSZ nanofibers enable real-time room-temperature NO2 gas sensor

Air pollution has emerged as a critical global issue, necessitating the development of effective real-time gas monitoring technologies. However, conventional gas sensors face limitations such as high energy consumption and sluggish response/recovery kinetics. In this study, we report a novel SnS2/Ag2S heterojunction supported by yttria-stabilized zirconia nanofibers (YSZ@SnS2/Ag2S) through a facile electrospinning, hydrothermal and subsequent cation-exchange method. This hierarchical composite nanofiber consists of well-distributed Ag2S quantum dots (QDs) attached to vertical anchored SnS2 nanosheets, forming an interconnected network supported by YSZ nanofibers. The integrated sensor exhibited high response of 3.27 and swift response/recovery times of 12/27 s to 1 ppm NO2 at room temperature, respectively. Benefited from highly permeable three-dimensional continuous conductive nanofibers, along with the hierarchical nanosheets/QDs structure, the gas transmission/diffusion and number of reactive sites were ensured. Additionally, the interfacial built-in electric field of SnS2/Ag2S heterojunction further enhanced the electron transfer, carrier migration and gas-sensitive reaction kinetics. This study provides insights into the development of functional composite nanofibers and paves the way for the exploitation of real-time room-temperature gas sensing applications.

Synergy between Lewis acidic metal sites and silanols in Sn- and Ti-Beta for conversion of butenes by DRIFTS

The synergistic effect of Lewis acidic Sn/Ti sites and silanols in Sn- and Ti-Beta zeolites on the reaction pathways and mechanisms of the conversion of butenes was investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy. The double bond migration reaction of n-butene to cis-2-butene followed an AB–AD mechanism, in which hydrogen abstraction (AB) from the methylene group at Lewis acidic Sn/Ti sites afforded an allyl intermediate, followed by synergistic hydrogen addition (AD) on silanols. In contrast, the following cis–trans isomerization reaction between cis-2-butene and trans-2-butene, and the activation of isobutene, followed an AD–AB mechanism via hydrogen addition to the double bond of butenes on silanols, forming an alkoxyl group rather than allyl group as the intermediate owing to the absence of a methylene group in 2-butene and isobutene.

Bicyclo[2.2.0]hexene: A Multicyclic Mechanophore with Reactivity Diversified by External Forces.

Polymer mechanochemistry has been established as an enabling tool in accessing chemical reactivity and reaction pathways that are distinctive from their thermal counterparts. However, eliciting diversified reaction pathways by activating different constituent chemical bonds from the same mechanophore structure remains challenging. Here, we report the design of a bicyclo[2.2.0]hexene (BCH) mechanophore to leverage its structural simplicity and relatively low molecular symmetry to demonstrate this idea of multimodal activation. Upon changing the attachment points of pendant polymer chains, three different C-C bonds in bicyclo[2.2.0]hexene are specifically activated via externally applied force by sonication. Experimental characterization confirms that in different scenarios of polymer attachment, the regioisomers of BCH undergo different activation reactions, entailing retro-[2+2] cycloreversion, 1,3-allylic migration, and retro-4π ring-opening reactions, respectively. Control experiments with small-molecule analogues reveal that the observed diversified reactivity of BCH regioisomers is possible only with mechanical force. Theoretical studies further elucidate that the differences in the positions of substitution between regioisomers have a minimal impact on the potential energy surface of the parent BCH scaffold. The mechanochemical selectivity between different C-C bonds in each constitutional isomer is a result of selective and effective coupling of force to the aligned C-C bond in each case.

The tandem catalysis of porous CoW composite oxide: Intensified allylic oxidation of cyclohexene to 2-cyclohexene-1-one

The controllable oxidation of the allylic CH bond has great academic and industrial value. Different Co/W ratios of CoW composite oxides were prepared using hydrothermal method and used in the allylic oxidation reaction of cyclohexene containing unstable allylic hydrogen atoms and carbon-carbon double bonds. The relationship between the structure of active sites and catalytic performance was revealed using characterization techniques such as XRD, N2 adsorption/desorption, SEM, TEM, FT-IR, UV–vis, and XPS. The results indicated that the Co(II)/Co(III) sites effectively mediate the first step of the entire oxidation reaction system, which generates hydroxyl radicals and peroxyl radicals through the activation of H2O2 to achieve chain initiation. Subsequently, the cyclohexene underwent a series of chain migration reactions under the action of hydroxyl radicals and peroxyl radicals, resulting in the formation of 2-cyclohexen-1-one and 2-cyclohexen-1-ol. Finally, 2-cyclohexen-1-ol interacted with W(VI) sites to form 2-cyclohexen-1-one via an alcohol-coordinated hydroxyl intermediate. The tandem oxidation reaction of cyclohexene allylic oxidation and 2-cyclohexen-1-ol dehydrogenation was realized by the CoW synergistic catalytic. The synergy between Co and W sites, composed of Co-O-W units on the surface of the CoW oxide with porous channel features, was elucidated. The experimental results showed that under the optimal conditions, using CoW composite oxide (Co/W = 1:1) as the catalyst, a 79.8% conversion rate of cyclohexene was achieved with 93.9% selectivity for the allylic products, among which the selectivity for 2-cyclohexen-1-one was 73.8%.

Application and Parameter Optimization of Electro-Kinetic Geosynthetics Electrodes Based on the Wild Horse Optimizer in Horizontal Electric Field Sludge Dewatering

This study systematically compared the performance of five corrosion-resistant electrode materials for electro-dewatering. Through a comprehensive analysis of dewatering efficiency, energy consumption, and corrosion resistance, conductive plastic composite electrodes (EKG) were selected as the optimal electrode material for experimentation. Additionally, the impact of electric field strength and electrode spacing on the efficiency and energy consumption of electro-dewatering (EDW) was investigated. The results showed that the increase in electric field intensity could improve the solid content and dewatering efficiency of the sediments, but the corresponding energy consumption also increased. The increased spacing of the plates reduced the dehydration effect and increased the energy consumption. By employing the Wild Horse Optimization algorithm, empirical and multifactorial response models for the dewatering solidification process were established, aimed at predicting the dewatering performance and energy consumption. The study concludes that for the remediation of heavy metals, the electric field strength should not exceed 10 V/cm to avoid excessive heavy metal migration and potential adverse chemical reactions.

In-situ decorated cobalt phosphide cocatalyst on Hittorf's phosphorus triggering efficient photocatalytic hydrogen production

Hittorf's phosphorus (HP) is a promising visible-light-driven photocatalyst, yet the slow charge migration and sluggish surface reaction kinetics have limited its photocatalytic hydrogen evolution reaction (HER) efficiency. In this work, cobalt phosphide (CoP2) modified rod-like HP (HP/CoP2) composite was designed and synthesized by a template-assisted chemical vapor deposition strategy. The optimal HP/CoP2 composite yields a HER rate reaching 13.1 μmol·h-1 through pure water splitting under visible light irradiation, which is approximately 4 times higher than that of HP using Pt as cocatalyst (3.3 μmol·h-1). It was experimentally indicated that the accelerated photogenerated charge transfer and promoted surface HER kinetics in the composite gave rise to the superior photocatalytic HER performance.

Two Synthesis Approaches of the 2H‐Tetrahydro‐4,6‐dioxo‐1,2‐oxazine Ring System of Alchivemycins A and B

AbstractThe 2H‐tetrahydro‐4,6‐dioxo‐1,2‐oxazine (TDO) ring, a rare structural motif embedded in the molecular architecture of alchivemycins, is synthesized from 2,2,6‐trimethyl‐4H‐1,3‐dioxin‐4‐one via two routes. Both routes involve the intramolecular trapping of an acylketene intermediate by an internal hydroxy group to form the TDO ring as a key step. The first synthesis was achieved in 29 % overall yield from the starting material by a four‐step sequence featuring a DMAP−CaCl2‐mediated O‐ to C‐acyl migration reaction to install an acyl group at the C5 position of the TDO ring. The second synthesis was completed in 8 % overall yield from the same starting material as the first one through five steps by exploiting a photo‐induced double bromination reaction.

Regulating carrier transfer route via 1D-2D junction on TiO2 nanorods intercalated with N-doped γ-graphyne nanosheets

One-dimensional TiO2 nanostructure has been widely studied in the domain of photoelectrochemical water splitting. Nevertheless, the wide bandgap and fast carriers recombination of TiO2 restrain its performance. In this study, two-dimensional N-doped γ-graphyne nanosheets were synthesized and employed in the reasonable design of TiO2 heterostructure, facilitating carrier migration and water oxidation reaction. The photocurrent density of photoanode composed of N-doped γ-graphyne/TiO2 nanorods reaches 1.48 mA cm−2, 1.72 times that of pristine TiO2 at a bias of 1.23 V (vs. RHE). Meanwhile, the calculated applied bias photon-to-current efficiency increases from 0.25 % to 0.56 %. The combination of TiO2 nanorods with layered semiconductive N-doped γ-graphyne contributes to the construction of charge transfer channels, regulating surface states and reaction sites, promoting the hole storage, and reducing the free energy barrier in the velocity determination process. This study sheds light on the design of N-doped γ-graphyne modified catalysts and facilitates their application in photoelectrochemical and photoelectrocatalytic fields.

Chromium-Catalyzed Cross-Coupling of Methyl Ketones with Cyclic Ketones toward the Selective Synthesis of β-Branched β,γ-Unsaturated Ketones.

Chromium-catalyzed cross-coupling of methyl ketones with cyclic ketones to β-branched β,γ-unsaturated ketones are reported. Interestingly, single-crossed aldol condensation products are formed, even in reactions in which a mixture of products is possible. The reaction is highly chemoselective and regioselective. This catalytic route gives a unique opportunity to integrate the chemistry of the synthetic challenge cross-coupling reaction of ketones and the alkene migration reaction into a reaction pot.

Iron(iv) alkyl complexes: electronic structure contributions to Fe–C bond homolysis and migration reactions that form N–C bonds from N2

Silylation of iron-alkyl-dinitrogen complexes gives high-spin iron(iv) products that also have an iron(ii) resonance structure. The stability and reactivity of these compounds depends on the alkyl group, with insertion and homolysis observed.

Synthesis of 2-substituted 3-trifluoromethylselenoindoles via a SeCF3 migration reaction

The synthesis of 2-substituted 3-trifluoromethylselenoindoles via a zinc-mediated SeCF3 migration is reported.

Electrochemical synthesis of β-difluoromethylamide compounds by N-benzenesulfonylacrylamide with difluorine reagents.

A mild and efficient electrochemical method for radical addition, cyclization, and migration reaction was described in this work. A difluoromethyl radical was produced by anodizing CF2HSO2Na. The resulting product was then added to olefin, underwent Smiles cyclization, and migrated to form β-difluoromethamide compounds after the release of SO2. The process was free from metals and catalysts, gram-grade, and resistant to a variety of electron-rich substrates.

Photocatalytic overall water splitting endowed by modulation of internal and external energy fields.

The pursuit of sustainable and clean energy sources has driven extensive research into the generation and use of novel energy vectors. The photocatalytic overall water splitting (POWS) reaction has been identified as a promising approach for harnessing solar energy to produce hydrogen to be used as a clean energy carrier. Materials chemistry and associated photocatalyst design are key to the further improvement of the efficiency of the POWS reaction through the optimization of charge carrier separation, migration and interfacial reaction kinetics. This review examines the latest progress in POWS, ranging from key catalyst materials to modification strategies and reaction design. Critical analysis focuses on carrier separation and promotion from the perspective of internal and external energy fields, aiming to trace the driving force behind the POWS process and explore the potential for industrial development of this technology. This review concludes by presenting perspectives on the emerging opportunities for this technology, and the challenges to be overcome by future studies.

CO insertion enabled γ-C(sp3)-H heteroarylative carbonylation of tertiary alcohols via heteroaryl migration.

The direct functionalization of remote C(sp3)-H is valuable but challenging, and is even more difficult to achieve than the γ-C(sp3)-H functionalization of alcohols. Among the strategies, hydrogen atom transfer (HAT) is one of the solutions for such transformations. Herein, we designed a migration reaction involving carbon monoxide, forming an alkoxy radical by photocatalysis, and used carbon monoxide to extend the carbon chain to provide a site for the migration of heteroaryl groups, which makes 1,4-HAT more advantageous, and we relied on this strategy to successfully achieve the synthesis of 1,4-dicarbonyl compounds by γ-C(sp3) functionalization of alcohols.

Theoretical kinetic studies on intramolecular H-migration reactions of peroxy radicals of diethoxymethane.

Diethoxymethane (DEM), a promising carbon-neutral fuel, has high reactivity at low temperatures. The intramolecular hydrogen migration reaction of the DEM peroxy radicals can be viewed as a critical step in the low temperature oxidation mechanism of DEM. In this work, multistructural transition state theory (MS-TST) was utilized to calculate the high-pressure limit rate constants of 1,5, 1,6 and 1,7 H-migration reactions for DEM peroxy radicals. In addition to the tunneling effects and anharmonic effects, the intramolecular effects, including steric hindrance, intramolecular hydrogen bonding and conformational changes in reactants and transition states, are also considered in the rate constant calculations. The calculated energy barriers and rate constants demonstrated the substantial impact of intramolecular effects on the kinetics of H-migration reactions in DEM peroxy radicals. Specifically, the distinct configurations of transition states could potentially influence the reaction kinetics. The pressure-dependent rate constants are computed using system-specific quantum RRK theory. The calculated results show that the falloff effect of 1,5 and 1,6 H-migration reactions is more pronounced than that of the 1,7 H-migration reaction. The thermodynamics and kinetics presented in this study could be instrumental in understanding the low-temperature oxidation mechanism of DEM and might prove crucial for future research on comprehensively analyzing the autoignition behavior.

Unprecedented single-electron-transfer reduction-based N → C acyl migration reactions of imides enabled by redox-neutral photocatalysis

N → C acyl migration: in the absence of a base, redox-neutral photocatalyzed acyl migration reactions have been realized via the reaction of N-vinylimides with alkyl radicals derived from alkyl silicates.

Distal iodine migration of arylalkynes via cyclic monoaryliodonium salts

A convenient synthesis of cyclic monoaryliodonium salts with readily obtained iodoethynylarenes is presented. ortho-Iodoarylacetylenes and 1,3-diynes are afforded in sequential one-pot iodine migration reactions directly from iodoethynylarenes via the in situ formed cyclic monoaryliodoniums.