Transition State Structures Research Articles

Theoretical investigation of Diels–Alder reaction mechanism and regioselectivity with functionalized fullerene derivatives

AbstractDensity functional theory (DFT) was used to study the mechanism of Diels–Alder (DA) reaction between 2‐Methyl‐ 1,3 Butadiene (MBD) with B12N12, B6N6C12 and B6C12N6 fullerens in the gas phase. In this mechanism, B‐N bonds of four‐membered and six‐membered rings of nanocages were chosen to react with MBD. Due to the existence of two types of B‐N bonds, two competitive pathways (a and b) were investigated. The effect of the substitution of carbon atoms instead of boron and nitrogen atoms on the stability of the structures and the regioselectivity of the DA reaction was examined. The potential energy of all structures and the activation barrier for all reaction pathways was evaluated. The chemical reactivity of fullerens using the molecular quantum descriptors was assessed. To evaluate the global electron density transfer in transition states (TS) structures, the natural bond orbital (NBO) analysis was performed.

An MEDT Study of the Reaction Mechanism and Selectivity of the Hetero-Diels-Alder Reaction Between 3-Methylene-2,4-Chromandione and Methyl Vinyl Ether.

The hetero-Diels-Alder (HDA) reaction between the ambident heterodiene 3-methylene-2,4-chromandione (MCDO) and non-symmetric methyl vinyl ether (MVE) is investigated using the molecular electron density theory (MEDT) at the B3LYP/6-311G(d,p) computational level. The aim of this study is to gain insight into its molecular mechanism and to elucidate the factors that control the selectivity found experimentally. DFT-based reactivity indices reveal that MCDO exhibits strong electrophilic characteristics, while MVE displays a strong nucleophilic character. Meanwhile, the Parr function explains the ortho regioselectivity of this HDA reaction. The highly polar nature of this HDA reaction, supported by the high global electron density transfer (GEDT) taking place at the transition state structures (TSs), accounts for the very low activation energy associated with the most favorable TS-4on. The ambident nature of MCDO allows for the formation of two constitutional isomeric cycloadducts. In the case of MVE, pseudocyclic selectivity is attained using a thermodynamic control. This polar HDA reaction displays an endo stereoselectivity and a complete ortho regioselectivity. A comparative relative interacting atomic energy (RIAE) analysis of the two diastereomeric structures TS-4on and TS-6on indicates a high degree of likeness, which explains the low pseudocyclic selectivity under kinetic control.

Acyl Transfer Reactions of 2,4-Dinitrophenyl Furoates: Comparative Effects of Nucleophiles and Non-Leaving Groups

This study investigated the acyl group transfer reactions of 2,4-dinitrophenyl 5-substituted-2-furoates, promoted by 4-substituted phenoxides/phenols in a 20 mol% DMSO aqueous solution at 25 °C. The reactions yielded nucleophilic substitution products and displayed second-order kinetics, with βacyl values ranging from −2.24 to −2.50, ρ(x) values between 3.18 and 3.56, and βnuc values of 0.81 to 0.84. These findings indicate an addition–elimination mechanism where the initial step is rate-determining. Comparative analysis with previous data revealed that the transition state structure remained largely consistent when altering the non-leaving group from thienyl to furyl under similar conditions. Notably, a shift in the rate-determining step was observed when changing the nucleophile from secondary amines/ammonium ions to 4-substituted phenoxides/phenols, highlighting the significant impact of nucleophile selection on the reaction kinetics and mechanisms in acyl transfer reactions.

Automatization of theoretical kinetic data generation for tabulated TS models building - Part 1: Application to 1,3-H-shift reactions

Estimation of kinetic parameters is a key aspect of chemical combustion modeling and several approaches were developed to approximate unknown data. In this work, a code in Python was developed to build tables of transition state (TS) models automatically for intramolecular H-shift reactions in alkyl radicals. The code generates the kinetic rules for all the possible combinations of methyl-substituted reactions based on the structures of the minimal, non-substituted, reactant, TS, and product. The code is able to create and differentiate multiple transition state configurations, considering the axial and equatorial positions for the cyclic substituents and including all the possible pathways for the reactions, which is shown to be an important feature in performing accurate automatic kinetic calculations. Each structure is automatically submitted to geometry optimization and electronic energy calculations, as well as the relaxed scans of the torsional modes identified by the code. From the results of electronic calculations, the rate constants for each pathway are obtained automatically by the application of the transition state theory with tunneling corrections, in a defined temperature range. The kinetic coefficients, as well as the modified Arrhenius parameters, are then assembled and organized to create a final table that connects the kinetic data with TS structure characteristics. These tables can be directly applied as a kinetic data source for reaction mechanism development. The ability of the code to generate reliable rate constants was tested for 1,3-H-shift reactions and the results were compared with theoretical data manually produced, and showed a good agreement. In particular, the code was able to create all the transition state configurations, with an exhaustive description of all possible reaction pathways, using a rigorous and systematic counting based on symmetry, stereocenters, and diastereomers. The proposed method leads to more accurate results on these aspects, compared to repetitive hand calculations of dozens of rate constants.

Accurately Predicting Barrier Heights for Radical Reactions in Solution Using Deep Graph Networks.

Quantitative estimates of reaction barriers and solvent effects are essential for developing kinetic mechanisms and predicting reaction outcomes. Here, we create a new data set of 5,600 unique elementary radical reactions calculated using the M06-2X/def2-QZVP//B3LYP-D3(BJ)/def2-TZVP level of theory. A conformer search is done for each species using TPSS/def2-TZVP. Gibbs free energies of activation and of reaction for these radical reactions in 40 common solvents are obtained using COSMO-RS for solvation effects. These balanced reactions involve the elements H, C, N, O, and S, contain up to 19 heavy atoms, and have atom-mapped SMILES. All transition states are verified by an intrinsic reaction coordinate calculation. We next train a deep graph network to directly estimate the Gibbs free energy of activation and of reaction in both gas and solution phases using only the atom-mapped SMILES of the reactant and product and the SMILES of the solvent. This simple input representation avoids computationally expensive optimizations for the reactant, transition state, and product structures during inference, making our model well-suited for high-throughput predictive chemistry and quickly providing information for (retro-)synthesis planning tools. To properly measure model performance, we report results on both interpolative and extrapolative data splits and also compare to several baseline models. During training and testing, the data set is augmented by including the reverse direction of each reaction and variants with different resonance structures. After data augmentation, we have around 2 million entries to train the model, which achieves a testing set mean absolute error of 1.16 kcal mol-1 for the Gibbs free energy of activation in solution. We anticipate this model will accelerate predictions for high-throughput screening to quickly identify relevant reactions in solution, and our data set will serve as a benchmark for future studies.

Post-Transition State Bifurcation Controls Torsional Selectivity in Radical Addition of Allenes.

Post-transition state bifurcation (PTSB) has received wide attention in the field of reaction mechanism research due to its role in producing nonstatistical reaction selectivity, which cannot be solely explained by transition state theory. Particularly, even subtle molecular motions such as bond torsion can precipitate PTSB, thereby significantly complicating the quantitative understanding of dynamic selectivity. In this work, we found that the radical addition of allenes is an elementary transformation that generally exhibits PTSB stereoselectivity, where a single radical addition transition state can lead to both Z- and E-allylic radicals via the post-transition state allylic single bond torsion. Interestingly, dynamic Z/E-selectivity favors the Z-allylic radicals, which contrasts the thermodynamic preference. Based on the dynamics study of twenty-five radical additions of mono-substituted allenes with diverse electronic and steric effects, we have identified that this dynamic stereoselectivity is synergistically controlled by the transition state structure and the differential trends within specific dimensions of the bifurcating reaction coordinates, which also holds true for di-substituted allene substrates. This study refines the mechanism of radical addition of allenes and underscores the importance of the differential trend of the reaction coordinates in controlling dynamic selectivity, offering a deeper insight into PTSB selectivity factors.

Accessing the Cloke-Wilson Rearrangement via Conjugate Addition of Phosphoranes to Michael Acceptors: A Route to Cyclopropanes and 5-Membered Ring Heterocycles Investigated by Density Functional and Ab Initio Theory.

Conjugate addition of unstabilized Wittig-type phosphonium ylides to 1,1-diacceptor- and 1-acceptor-substituted alkenes is investigated by density functional theory and high-level ab initio (DLPNO-CCSD(T)) calculations. The results indicate that the initial conjugate addition step should be facile with barriers predicted to be between 0 and 21 kcal mol-1. Potential intramolecular follow-up reactions include the formation of acceptor-substituted cyclopropanes as well as the formation of dihydrofuran derivatives via intramolecular SN2-type transition state structures. The barriers calculated for these potentially valuable cyclization reactions are substantial with Gibbs free energies of activation between 19 and 40 kcal mol-1. Competing reaction channels include Wittig olefination (for ketones and aldehydes), as well as Claisen condensation reactions. The reaction offers an alternative entry point to the nucleophile-catalyzed Cloke-Wilson rearrangement.

The origin of selectivity in the trimerization of 1,3-cyclopentadiene from an activation strain perspective.

Quantum chemical modeling (DFT-PBE0/cc-pVTZ) of the [4 + 2]-cycloaddition reaction of 1,3-cyclopentadiene (CPD) to (exo/endo)-dicyclopentadiene (DCPD) was carried out, resulting in 14 products-CPD trimers. According to calculations, exo-addition of CPD to the norbornene (NB) fragment of DCPD and trans-addition of CPD to the cyclopentene (CP) fragment of DCPD are kinetically preferred. Ring strain energies ERS were calculated for all trimers using the homodesmotic reaction approach. The least strained trimers are formed by exo-addition of CPD to the NB fragment of exo-DCPD, while the most strained ones are formed by endo-addition of CPD to the NB fragment of endo-DCPD. ERS values are in good agreement with thermodynamic stability of trimers. Analysis of activation energy using the activation strain model showed steric effects causing deformation of the DCPD molecule upon reaching the transition state to be the leading factor of the magnitude of the cycloaddition reaction activation barrier. Deformation of the DCPD molecule mostly occurs in two dihedral angles-the angle of escape of H atoms from the plane of the double bond involved in cycloaddition and the angle between the NB and CP fragments. The sum of deviations of these angles in the transition states (or products) structures is in good agreement with Gibbs activation energies of cycloaddition reactions of CPD to DCPD. Quantum chemical calculations were carried out using density functional theory in Gaussian 09 software. Hybrid exchange-correlation PBE0 functional was used with cc-pVTZ basis set.

Electronic Force Density Fields: Insights into Partial Bonds, Transition States, and Chemical Structure Evolution.

This paper presents the quantum-topological binding approach, in which the electrostatic and total static force density fields, Fes(r) and , together with the electron density gradient field ∇ρ(r), are simultaneously analyzed to elucidate the chemical structure of transition states and the nature of interatomic interactions for semibroken semiformed partial chemical bonds. The approach attributes the discrepancies between the force fields and Fes(r) to the nonclassical electron-electron interaction effects. The internuclear gap between the zero-flux boundaries of Fes(r) and ∇ρ(r) indicates the interatomic charge transfer phenomenon (ICT) that occurs upon the formation of a system from free atoms. Concomitantly, the mismatch of the zero-flux surfaces defined in and ∇ρ(r) can be interpreted as a phenomenon of the electron-transfer-induced quantum chemical response (QCR), which originates from the electron exchange correlation. Our study permits the assertion of parallels between partial bonds and noncovalent interactions, as both typically exhibit incomplete QCRs, indicating the partial electron sharing of the transferred density. The changes in atomic and pseudoatomic charges are employed to describe the evolution of the chemical structure upon the substitution reaction. It is observed that the acquired difference in the actual atomic electronegativity causes polarization upon the heterolytic breaking of virtually nonpolar bonds. It is further proposed that the proximity of closely related stationary states along the reaction path on a potential energy hypersurface implies their similarity in the manifestation of the ICT and sympathetic QCR. Furthermore, the involvement of an electron pair in a partial bond facilitates its delocalization through the attraction by the static forces and Fes(r) to a neighboring nucleus and through the smearing by the Pauli kinetic force FP(r).

Force-Free Identification of Minimum-Energy Pathways and Transition States for Stochastic Electronic Structure Theories.

The accurate mapping of potential energy surfaces (PESs) is crucial to our understanding of the numerous physical and chemical processes mediated by atomic rearrangements, such as conformational changes and chemical reactions, and the thermodynamic and kinetic feasibility of these processes. Stochastic electronic structure theories, e.g., Quantum Monte Carlo (QMC) methods, enable highly accurate total energy calculations that in principle can be used to construct the PES. However, their stochastic nature poses a challenge to the computation and use of forces and Hessians, which are typically required in algorithms for minimum-energy pathway (MEP) and transition state (TS) identification, such as the nudged elastic band (NEB) algorithm and its climbing image formulation. Here, we present strategies that utilize the surrogate Hessian line-search method, previously developed for QMC structural optimization, to efficiently identify MEP and TS structures without requiring force calculations at the level of the stochastic electronic structure theory. By modifying the surrogate Hessian algorithm to operate in path-orthogonal subspaces and at saddle points, we show that it is possible to identify MEPs and TSs by using a force-free QMC approach. We demonstrate these strategies via two examples, the inversion of the ammonia (NH3) molecule and the nucleophilic substitution (SN2) reaction F- + CH3F → FCH3 + F-. We validate our results using Density Functional Theory (DFT)- and Coupled Cluster (CCSD, CCSD(T))-based NEB calculations. We then introduce a hybrid DFT-QMC approach to compute thermodynamic and kinetic quantities, free energy differences, rate constants, and equilibrium constants that incorporates stochastically optimized structures and their energies, and show that this scheme improves upon DFT accuracy. Our methods generalize straightforwardly to other systems and other high-accuracy theories that similarly face challenges computing energy gradients, paving the way for highly accurate PES mapping, transition state determination, and thermodynamic and kinetic calculations at significantly reduced computational expense.

Temperature effects on the branching dynamics in the model ambimodal (6 + 4)/(4 + 2) intramolecular cycloaddition reaction.

C14H20 (tetradecapentaene) is a simple model system exhibiting post transition-state behavior, wherein both the (6 + 4) and (4 + 2) cycloaddition products are formed from one ambimocal transition state structure. We studied the bifurcation dynamics starting from the two ambimodal transition state structures, the chair-form and boat-form, using the quasi-classical trajectory, classical molecular dynamics, and ring-polymer molecular dynamics methods on the parameter-optimized semiempirical GFN2-xTB potential energy surface. It was found that the calculated branching fractions differ between the chair-form and boat-form due to the different nature in the IRC pathways. We also investigated the effects of temperature on bifurcation dynamics and found that, at higher temperatures, trajectories stay longer in the intermediate region of the potential energy surface.

Understanding the Electronic Effects of Lewis Acid Catalysts in Accelerating Polar Diels-Alder Reactions.

The electronic effects of Lewis acid (LA) catalysts in reducing the activation energies of polar Diels-Alder (P-DA) reactions have been studied within Molecular Electron Density Theory. To this end, a quantum topological energy partitioning scheme, namely, the Relative Interacting Atomic Energy (RIAE) analysis, is applied to the transition state structures (TSs) and the ground state of the reagents of two different LA-catalyzed P-DA reactions. Analyses of the ξEtotalX total energies of the two interacting frameworks f(X) show that the electronic energy stabilization of the electrophilic frameworks, resulting from the global electron density transfer (GEDT), is the cause of an effective decrease of the activation energies. On the other hand, an in-depth analysis of the ξEintraA intra-atomic energies of the atoms belonging to the electrophilic ethylenic framework in the LA-catalyzed P-DA reactions of cyclopentadiene with acrolein indicates that the strong electronic stabilization of the carbonyl carbon, resulting from the GEDT taking place at the TSs, is the main factor responsible for the decrease of the activation energies in these LA-catalyzed P-DA reactions. Finally, the increase in GEDT at the TSs of these P-DA reactions causes an increase in the larger C-C distance, resulting from the stabilization of the electrophilic framework, thereby decreasing the suggested Pauli repulsion.

First‐Principle Calculation of the Hydrogen Adsorption and Diffusion Characteristics at an Ni3Al/Ni Interface

ABSTRACTThe occurrence of hydrogen embrittlement often leads to significant fracturing in materials. Thus, a comprehensive understanding of the interactions of hydrogen and its effects on material properties is essential. In this study, first‐principle calculations based on density functional theory are conducted to investigate the adsorption and diffusion characteristics of hydrogen at the Ni/Ni3Al(γ/γ') interface of a Ni‐based single‐crystal superalloy. The results show that hydrogen can stably adsorb onto the γ/γ′ interface, nearby octahedral interstitial sites, and tetrahedral interstitial sites in the γ‐phase. Analysis of the density of states and charge density confirms that the hydrogen atoms formed covalent bonds and ionic bonds with nearby Al atoms. A transition state structure search based on linear synchronous transit (LST) and quadratic synchronous transit (QST) models is utilized to calculate the diffusion paths and energy barriers of the hydrogen atoms between the stable adsorption sites near the interface. In addition, the permeation characteristics of hydrogen atoms at the interface are analyzed. Furthermore, it is confirmed that hydrogen atoms entering the matrix from the interface preferentially occupy the positions of the regular octahedral interstitial sites, diffuse towards adjacent regular 6Ni octahedral interstitial sites through the inclined octahedral interstitial sites between the atomic layers, and converge at the interface.

Both N-F oxidant and NaF determined reaction yield in the organoselenium-catalyzed oxidative ring-closing reaction of unsaturated alcohol: A theoretical study

An organoselenium-catalyzed oxidative exo-selective ring-closing reaction of unsaturated alcohol promoted by 1-fluoropyridinium triflate (FP-OTf), N-fluorobenzenesulfonimide (NFSI) and Selectfluor has been theoretically studied. The reaction mechanisms were proposed after detailed computational screening, the corresponding potential Gibbs energy surfaces were drawn, and catalytic cycles were proposed. The conjugation effect in ring-closing transition state structure determined the reaction exo-/endo- selectivity, and the intramolecular steric repulsion in β-elimination transition state structure determined the reaction (E)-/(Z)- selectivity. The influence of oxidant species and addition of NaF on the reaction yield was discussed in detail.

Study on dynamic behavior of atomic diffusion at interface between TiAlN coating and WC matrix

The molecular dynamics method was used to simulate the dynamic behavior change of atomic diffusion at interface between TiAlN coating and WC matrix in the carbide tool with TiAlN coating. It was determined that the one-way diffusion of C atom to TiAlN coating resulted in serious lattice distortion on the surface. Meanwhile, the whole diffusion process was accompanied by the continuous increase of stress, resulting in gradual deformation of the material. The interface bonding performance also decreases. Then, the surface energy and atomic layer convergence are calculated by the first-principles method. The TiAlN crystal surface is stable at 8 atomic layers, and the WC crystal surface is stable at 6 atomic layers, and then a stable microinterface model can be built. The relaxation processing for the established model was performed to determine the diffusion path of C atom. Then, the energy barrier, adhesion work, interface energy and fracture toughness of different transition state structures in the diffusion path of C atom are calculated, and it is determined that with the deepening of the diffusion of C atom in the coating, the binding ability of the interface of the coating base and the performance of the coating tool are more and more serious damage. Finally, the cutting experiment of TiAlN coated tool is designed. According to the surface topography of TiAlN coated tool in different periods, the simulation and theoretical analysis mentioned above are verified, which provides a theoretical basis for the subsequent research on improving the performance of coated tool.

Ketalization mechanism of glycerol to biobased glycerol levulinate ketal over HZSM-5: A combined experimental and theoretical study

Methyl levulinate ketal (MLK) is a novel biobased chemical derived from glycerol via ketalization, and exploring its synthesis mechanism is of great significance for the high-value utilization of biomass resources. In this study, the ketalization reaction of glycerol was evaluated using the MLK yield calculated by the GC internal standard method. The acidity of HZSM-5 was determined by NH3-TPD. The catalyst screening experiments demonstrated that HZSM-5 in zeolites and AlCl3 in metal salts exhibited high catalytic activity in the synthesis of MLK. Furthermore, the kinetic results indicated that the HZSM-5 zeolite catalyst exhibited a lower apparent activation energy in catalyzing the synthesis of MLK compared to the metal salt catalyst AlCl3. The ketalization reactions of levulinate and glycerol catalyzed by different types of acidic sites in HZSM-5 were then investigated using the density functional theory method. A comprehensive catalytic path, free energy changes, intermediates, and transition state structures were proposed. Furthermore, the free energy barriers of ethyl levulinate ketal and butyl levulinate ketal catalyzed by HZSM-5 were calculated, and the difference between the steric hindrance effect and the electronic effect of alkyl in levulinate was compared. This study enhances the understanding of ketalization reactions and will be useful in future catalyst design studies.

Dynamics of Elementary Steps on Metal Surfaces at High Coverages: The Prevalence and Kinetic Competence of Contiguous Bare-Atom Ensembles.

The rate of elementary steps on densely-covered surfaces depends sensitively on repulsive interactions within dense adlayers, situations ubiquitous in practice and with kinetic consequences seldom captured by Langmuirian treatments of surface catalysis. This study develops an ensemble-based method that assesses how such repulsion influences the prevalence and kinetic competence of bare-atom ensembles of different size. Chemisorbed CO (CO*) is used as an example because it forms dense adlayers on metal nanoparticles during CO2 hydrogenation (CO2-H2) and other reactions, leading to significant repulsion that weakens the binding of CO* and kinetically-relevant transition states (TS). This approach is enabled by density functional theory and probability formalisms and describes the prevalence of ensembles of contiguous bare atoms from their formation energy (via CO* desorption); it then determines their competence in stabilizing the TS and mediating the reaction rates. The specific conclusions reflect the extent to which a given TS and CO* desorbed to form bare ensembles "sense" repulsion and the contribution of each ensemble size to each reaction channel mediated by distinct TS structures. These formalisms are illustrated by assessing the relative contributions, kinetic relevance, and ensemble size requirements for two CO2-H2 routes (direct and H-assisted CO2 activation to CO and H2O) on Ru nanoparticles, but they are not restricted to specific bound species or reaction channels. This method is essential to assess the kinetic relevance of elementary steps in a given catalytic sequence and to determine the contributions from parallel reaction channels at the crowded surfaces that prevail in the practice of surface catalysis.

Harvesting nucleating structures in nanoparticle crystallization: The example of gold, silver, and iron.

The thermodynamics and kinetics of nanoparticle crystallization, as opposed to bulk phases, may be influenced by surface and size effects. We investigate the importance of such factors in the crystallization process of gold, silver, and iron nanodroplets using numerical simulations in the form of molecular dynamics combined with path sampling. This modeling strategy is targeted at obtaining representative ensembles of structures located at the transition state of the crystallization process. A structural analysis of the transition state ensembles reveals that both the average size and location of the critical nucleation cluster are influenced by surface and nanoscale size effects. Furthermore, we also show that transition state structures in smaller nanodroplets exhibit a more ordered liquid phase, and differentiating between a well-ordered critical cluster and its surrounding disordered liquid phase becomes less evident. All in all, these findings demonstrate that crystallization mechanisms in nanoparticles go beyond the assumptions of classical nucleation theory.

Electrocatalytic Performance of 2D Monolayer WSeTe Janus Transition Metal Dichalcogenide for Highly Efficient H2 Evolution Reaction.

Nowadays, the development of clean and green energy sources is the priority interest of research due to increasing global energy demand and extensive usage of fossil fuels, which create pollutants. Hydrogen has the highest energy density by weight among all chemical fuels. For the commercial-scale production of hydrogen, water electrolysis is the best method, which requires an efficient, cost-effective, and earth-abundant electrocatalyst. Recent studies have shown that the 2D Janus transition metal dichalcogenides (JTMDs) are promising materials for use as electrocatalysts and are highly effective for electrocatalytic H2 evolution reaction (HER). Here, we report a 2D monolayer WSeTe JTMD, which is highly effective toward HER. We have studied the electronic properties of 2D monolayer WSeTe JTMD using the periodic hybrid DFT-D method, and a direct electronic band gap of 2.39 eV was obtained. We have explored the HER pathways, mechanisms, and intermediates, including various transition state (TS) structures (Volmer TS, i.e., H*-migration TS, Heyrovsky TS, and Tafel TS) using a molecular cluster model of the subject JTMD noted as W10Se9Te12. The present calculations reveal that the 2D monolayer WSeTe JTMD is a potential electrocatalyst for HER. It has the lowest energy barriers for all the TSs among other TMDs. It has been shown that the Heyrovsky energy barrier (= 8.72 kcal mol-1) in the case of the Volmer-Heyrovsky mechanism is larger than the Tafel energy barrier (= 3.27 kcal mol-1) in the Volmer-Tafel mechanism. Hence, our present study suggests that the formation of H2 is energetically more favorable via the Volmer-Tafel mechanism. This study helps to shed light on the rational design of 2D single-layer JTMD, which is highly effective toward HER, and we expect that the present work can be further extended to other JTMDs to find out the improved electrocatalytic performance.

Phototriggered Generation of Ynol Ethers and Their Rearrangement to Ketenes.

This study developed reactions for the phototriggered generation of reactive ynol ethers using alkoxycyclopropenones. The resulting ynol ethers underwent rearrangement to ketenes, which subsequently participated in cycloaddition with alkynes and the acylation of amines. The alkoxy groups in the ynol ethers significantly influenced on the reactivity toward their rearrangement to ketenes. Reasonable transition state structures for the rearrangement reaction were found through density functional theory calculations, and the reactivity of the ynol ethers could be predicted by these calculations.