Homogeneous Metal Research Articles

Investigating the influence of smoothing approximations on analytical models of elastic waves in strongly scattering polycrystals

Ultrasonic scattering-based measurements are commonly used as sensitive tools for non-destructive evaluation (NDE) of metals. Existing analytical models can predict ultrasonic wavespeed and attenuation for statistically homogeneous metals exhibiting spatially dependent elastic constants. These models rely on two-point statistics that correspond to first-order smoothing approximation (FOSA) of the mass operator series present in the governing Dyson equation. The FOSA-based prediction agrees well with finite element (FE) results for a wide range of polycrystalline metals at ultrasonic frequencies in the stochastic regime. However, discrepancies become more pronounced with increasing single-crystal elastic anisotropy even at low frequencies in the Rayleigh limit. For example, a difference of 70% is present for Lithium. In this presentation, the next order or third-order smoothing approximation (TOSA) is introduced, and Rayleigh-limit attenuations and wavespeeds are derived analytically. In this context, the TOSA accounts for four-point correlation functions and, thus, a higher degree of multiple scattering effects are included. This presentation will focus on key points and assumptions pertaining to the derivation for results including the TOSA. The TOSA-based model improves predictions of longitudinal attenuation by more than 11% and 4% for polycrystalline Lithium or Nickel, respectively. Future extensions to higher frequencies and multiphase polycrystals will be described.

Uniform Na Metal Plating/Stripping Design for Highly Reversible Solid-State Na Metal Batteries at Room Temperature.

Solid-state alkaline metal batteries are highly sought outfor their improved energy density and security over the current lithium-ion batteries. However, their practical application is heavily hindered by the interfacial issues originating from the solid electrolyte/electrode mismatch. This work demonstrates that a CuO coating layer as an active interphase can thoroughly promote the intimate contact between a Na3 Zr2 Si2 PO12 solid electrolyte and a Na metal anode through an in situ conversion reaction. The resultant Cu/Na2 O matrix forms a mixed electron/ion conducting scaffold, which facilitates stable and homogeneous Na metal plating without dendrite formation. Moreover, the symmetric Na metal cell realizes impressively steady plating/stripping cycles for 5000h even under a high current density of 0.3mA cm-2 . The novelty is further manifested as a room-temperature solid-state Na metal full battery of Na3 V1.5 Al0.5 (PO4 )3 |CuO@NZSPO|Na is assembled and exhibits a highly reversible cyclability (99.85% coulombic efficiency and 99.0% capacity retention) under a charge/discharge rate of 5 C for 2250 cycles. This work effectively solves the interfacial issues at the Na metal/solid electrolyte interface and provides a convenient way toward high-performance solid-state Na metal batteries operated at room temperature.

Selective and quantitative functionalization of unprotected α-amino acids using a recyclable homogeneous catalyst

<h2>Summary</h2> A new Ir(III)-NHC catalyst is reported that shows remarkable activity in the <i>N</i>-alkylation of unprotected amino acids. The catalytic system gives excellent selectivity toward monoalkylated α-amino acids and a high degree of retention of stereochemistry. A wide range of unprotected nonnatural amino acids have been prepared. These compounds represent an array of building blocks that could be used for the direct synthesis of peptidomimetics. The synthesis of amino-acid-based surfactants is also reported. This catalytic method gives the amino acid products in quantitative yield; hence, tedious purifications by derivatization are therefore avoided. Furthermore, although the catalyst is a homogeneous metal complex, it can be recycled and reused for several runs. This also contributes to the efficiency and sustainability of the method.

Atomic-Scale Homogeneous RuCu Alloy Nanoparticles for Highly Efficient Electrocatalytic Nitrogen Reduction.

Ruthenium (Ru) is the most widely used metal as an electrocatalyst for nitrogen (N2 ) reduction reaction (NRR) because of the relatively high N2 adsorption strength for successive reaction. Recently, it has been well reported that the homogeneous Ru-based metal alloys such as RuRh, RuPt, and RuCo significantly enhance the selectivity and formation rate of ammonia (NH3 ). However, the metal combinations for NRR have been limited to several miscible combinations of metals with Ru, although various immiscible combinations have immense potential to show high NRR performance. In this study, an immiscible combination of Ru and copper (Cu) is first utilized, and homogeneous alloy nanoparticles (RuCu NPs) are fabricated by the carbothermal shock method. The RuCu homogeneous NP alloys on cellulose/carbon nanotube sponge exhibit the highest selectivity and NH3 formation rate of ≈31% and -73μmol h-1 cm-2 , respectively. These are the highest values of the selectivity and NH3 formation rates among existing Ru-based alloy metal combinations.

Dynamical Origin for the Collinder 132–Gulliver 21 Stream: A Mixture of Three Comoving Populations with an Age Difference of 250 Myr

We use Gaia DR3 data to study the Collinder 132–Gulliver 21 region via the machine-learning algorithm StarGO and find eight subgroups of stars (ASCC 32, Collinder 132 gp 1–6, Gulliver 21) located in close proximity. Three comoving populations were identified among these eight subgroups: (i) a coeval 25 Myr old moving group (Collinder 132), (ii) an intermediate-age (50–100 Myr) group, and (iii) the 275 Myr old dissolving cluster Gulliver 21. These three populations form parallel diagonal stripe-shape overdensities in the U–V distribution, which differ from open clusters and stellar groups in the solar neighborhood. We name this kinematic structure the Collinder 132–Gulliver 21 stream, as it extends over 270 pc in the 3D space. The oldest population, Gulliver 21, is spatially surrounded by the Collinder 132 moving group and the intermediate-age group. Stars in the Collinder 132–Gulliver 21 stream have an age difference up to 250 Myr. Metallicity information shows a variation of 0.3 dex between the youngest and oldest populations. The formation of the Collinder 132–Gulliver 21 stream involves both star formation and dynamical heating. The youngest population (Collinder 132 moving group) with homogeneous metallicity is probably formed through filamentary star formation. The intermediate-age and oldest populations were then scattered by the Galactic bar or spiral structure resonance to intercept Collinder 132's orbit. Without mutual interaction between each population, the three populations are flying by each other currently and will become three distinct groups again in ∼50 Myr.

Molecular Organosulphur, Organoselenium and Organotellurium Complexes as Homogeneous Transition Metal Catalytic Systems for Suzuki Coupling

AbstractDuring last two decades, researchers have employed organochalcogen compounds as ligands for the development of pre‐formed chalcogen ligated molecular complexes. During 2013–2020, various chalcogen containing homogenous catalytic systems for Suzuki Miyaura cross‐coupling reaction have been synthesized. The review provides insights into the synthetic methodologies for the preparation of organochalcogen ligands and their transition metal complexes. Another central aspect discussed is the application of such catalytic systems in Suzuki Miyaura coupling. Rationalization about the effect of temperature, substrate scope, organoborane derivatives and aryl halides employed has been elaborated. Effect of binding mode, ligand framework, chalcogen donor atom, metal and many other aspects that influence the catalytic potential of various systems have also been covered. Various other aspects such as green catalysis, use of non‐conventional energy sources have also been analyzed.

Recent Metal-Catalyzed Methods for Thioether Synthesis

AbstractThis review summarizes the more recent methods (since 2015) for the synthesis of thioethers using homogeneous metals as catalysts. The thioether moiety can be found in numerous compounds for pharmaceutical, agricultural, or material applications and it is therefore important to develop new, efficient methods for their synthesis. The recent efforts in this field focus on the use of non-precious metal catalysts, as well as on the development of new bond-forming processes.1 Introduction2 Cross-Couplings3 C–H Activation4 Hydrothiolation5 Carbothiolation6 Miscellaneous7 Conclusion

Supercritical water gasification of hyperaccumulators for hydrogen production and heavy metal immobilization with alkali metal catalysts

The high moisture content and heavy metal concentration of hyperaccumulator are the main bottlenecks of resource utilization. Supercritical water gasification technology was used to convert Sedum plumbizincicola (a hyperaccumulator of Zn and Cd) into hydrogen gas and to immobilize HMs into biochar. Homogeneous alkali metal catalysts such as NaOH, Na2CO3 and Ca(OH)2 were added to optimize the experimental conditions. The results showed that NaOH was effective in capturing CO2in-situ, thereby shifting the water-gas shift reaction equilibrium in the forward direction. And the increase of NaOH concentration had a significant promotion effect on hydrogen production. In the non-catalytic gasification of Sedum plumbizincicola, the highest hydrogen (1.5 mol/kg) and H2 selectivity (22.9%) with greater carbon gasification efficiency (19.3%) and lower H2 gasification efficiency (8.7%) of the gas products were obtained at 400 °C with 6 wt% material concentration for 20 min. However, NaOH at 5% mass fraction maximized hydrogen and H2 selectivity up to 7.5 and 98.2%, respectively. Alkali catalyst not only promoted the generation of hydrogen-rich bio-gas but also enhanced the immobilization efficiency of heavy metals. Compared to non-catalytic, when the addition amount of NaOH was 1 wt%, the Zn、Mn、Cd、Pb、Cr accumulated in biochar increased significantly for 76.8, 42.5, 80.8, 75.6 and 80.0%, respectively. This study highlights the remarkable ability of SCWG with alkali catalyst for hydrogen production and heavy metal stabilization.

Production of nickel-rich LiNi0.89Co0.08Al0.03O2 cathode material for high capacity NCA/graphite secondary battery fabrication

Abstract Li-ion secondary battery is highly recommended as a power source to highly advanced battery electric vehicles. Among various types, the lithium nickel cobalt aluminum oxide (NCA) battery is considered suitable for high energy and power application. In this study, the NCA cathode material LiNi0.89Co0.08Al0.03O2 was produced via the oxalate co-precipitation technique to reduce the overall production cost and process complexity. Oxalic acid and a small amount of sodium hydroxide were used as the precipitant and pH regulator, respectively. Homogenous and loose metal oxalate precipitate formation was confirmed by X-ray diffraction (XRD), scanning electron microscopy, and Fourier-transform infrared spectroscopy analysis. XRD patterns of the as-obtained micron-sized NCA showed a well-layered hexagonal structure. The electrochemical properties of the cathode in the full cell were thoroughly examined. The specific discharge capacity of the as-obtained NCA in NCA/LiPF6/graphite at a current rate of 20 mA/g was 142 mAh/g. The as-prepared NCA sample had capacity retention of 80% after being charged and discharged at 0.1 A/g for 101 cycles. Scaling up of NCA production process to 2 kg per batch was conducted and evaluation of NCA product quality was performed by material characterization. Based on the overall results and considering the overall process, such an approach is expected to be developed and improved for future large-scale production purposes.

Ca II triplet spectroscopy of Small Magellanic Cloud red giants

Aims. In this paper we analyze the chemical evolution of the main body of the SMC, adding six additional clusters to previously published samples, based on homogeneously determined and accurate metallicities. Methods. We derived radial velocities and Ca II Triplet (CaT) metallicity of more than 150 red giants stars in six SMC star clusters and their surrounding fields, with the instrument GMOS on GEMINI-S. The mean cluster radial velocity and metallicity were obtained with mean errors of 2.2 km s−1 and 0.03 dex, while the mean field metallicities have a mean error of 0.13 dex. We add this information to that available for another 51 clusters and 30 fields with CaT metallicities on the same scale. Using this expanded sample we analyze the chemical properties of the SMC main body, defined as the inner 3.4° in semimajor axis. Results. We found a high probability that the metallicity distribution of the main body clusters is bimodal with a metal-rich and a metal-poor cluster group, having mean metallicities with a dispersion of μ = −0.80, σ = 0.06 and μ = −1.15, σ = 0.10 dex, respectively. On the other hand, main body field stars show a unimodal metallicity distribution peaking at [Fe/H] ∼ −1 and dispersion of 0.3. Neither metal-rich nor metal-poor clusters present a metallicity gradient. However, the full main body cluster sample and field stars have a negative metallicity gradient consistent with each other, but the one corresponding to clusters has a large error due to the large metallicity dispersion present in the clusters studied in that region. Metal-rich clusters present a clear age–metallicity relation, while metal-poor clusters present no chemical enrichment throughout the life of the galaxy. Conclusions. We present observational evidence that the chemical enrichment is complex in the SMC main body. Two cluster groups with potential different origins could be coexisting in the main body. More data with precise and homogeneous metallicities and distances are needed and dynamical simulations are required to understand the possible different origins for the two cluster groups.

Synthesis of Aryl/Heteroaryl Selenides Using Transition Metals Catalyzed Cross Coupling and C─H Activation

Abstract:Aryl and heteroaryl selenides are an important class of organic compounds and their synthesis has been widely studied all over the world in the last two decades. Transition metals catalysed cross-coupling and directed C─H activation in unactivated arenes in the presence of diselenides/aryl selenols are found to be the most important tools for their synthesis. In recent years different transition metal catalysts were found to be effective to perform C─Se crosscoupling in both aryl and heteroaryl rings. The present review article covers all the recent advances made in the last ten years in the field of the synthesis of aryl and heteroaryl selenides through homogeneous and heterogeneous transition metals catalyzed cross-coupling reactions and directed selenylation via C─H bond activations.

Simulation of the heat transfer performance of Al2O3–Cu/water binary nanofluid in a homogenous copper metal foam

Simulation of the heat transfer performance of Al2O3–Cu/water binary nanofluid in a homogenous copper metal foam

Binucleating Bis(pyrazolyl)alkane Ligands and Their Cationic Dizinc Complexes: Modular, Bimetallic Catalysts for Ring-Opening Polymerization

Binucleating ligands enable the rational study and utilization of metal–metal cooperativity in catalysis through discrete bimetallic complexes. However, binucleating ligands rarely show the degree of structural modularity required for detailed optimization or structure–activity analysis, which are fundamental to homogeneous metal catalysis. This report introduces a highly modular family of binucleating proligands (1-R) consisting of two bis(pyrazolyl)alkanes bridged by a phenol. We prepared this series of proligands with variable substituents (R = −H, −Me, −Ph, −iPr) at the pyrazole 3-position in good yields by nucleophile-catalyzed condensation between 2,6-diformyl-4-(tert-butyl)-phenol and the corresponding bis(pyrazolyl)methanones. Cationic dizinc complexes 6-R were then prepared by treating proligands 1-R with diethylzinc and trityl salts. We fully characterized complex 6-H by single-crystal X-ray diffraction, identifying a twisted structure and modeling its conformational dynamics by density functional theory. The zinc atoms in 6-H are distorted tetrahedral, favorable for main group metals. Catalytic comparison identified 6-H as the most active and controlled catalyst for lactide and ε-caprolactone polymerization, resulting in low dispersity, end-group incorporation, and block copolymerization. Complexes 6-R represent the first atom-bridged bis(pyrazolyl)alkane bimetallics and constitute a highly modular platform for the rational investigation of dinuclear main group catalysis.

Atomistic simulations of plasticity heterogeneity in gradient nano-grained FCC metals

Gradient nano-grained (GNG) metals are an emerging class of heterogeneous structured materials with extraordinary mechanistic performances and unnatural plasticity mechanisms, which are unachievable in traditional homogeneous nanocrystalline metals. Here, the metal-type dependence of plasticity heterogeneity in three different GNG structured face-centered cubic metals (Cu, Al, and Ni) was studied by large-scale molecular dynamic simulation, from the plasticity perspectives of dislocation, deformation twinning, and grain boundary. The dislocation and deformation twinning-based plasticity show clear metal-type dependence in GNG structure of different selected metals. For grain boundary activities, GNG Cu, Al, and Ni are equivalent in the overall grain boundary sliding and micro-cracking process, but GNG Ni shows markedly higher grain boundary-free volume and stress due to the grain size gradient-induced twinning process. We find that GNG Al shows the weakest plasticity-induced strengthening due to its weak strain hardening and ununiform plasticity distribution, while GNG Ni exhibits prominent plasticity-induced strengthening because of the obvious extra strain hardening process. Besides, we further discuss the reasonable gradient grain size design of GNG structure, considering the critical grain size of the Hall-Petch and inverse Hall-Petch relationship, which will demonstrate a more rational plasticity heterogeneity and internal atomic stress distribution.

Electrochemical Surface Treatment to Enhance the Activity and Stability of Ni-P/CFP Electrocatalysts in Hydrogen Evolution Reaction

To construct an efficient and eco-friendly hydrogen economy, it is necessary to improve a cost competitiveness of green hydrogen. In this respect, a water electrolysis has been considered as an ideal production method of green hydrogen, where hydrogen evolution reaction (HER) is an irreplaceable cathodic reaction, while the various oxidative reactions such as oxygen evolution reaction (OER) or chlorine evolution reaction (CER) can be coupled as an anodic reaction. Because the HER becomes an essential reaction of water electrolysis, to facilitate efficient HER is one of the most important goal in a water electrolysis, in particular, to adopt and design the cost-effective HER catalysts are needed to lower the high activation energy of HER.As a theoretical and practical researches, a platinum (Pt) based compound is known as the most effective catalyst which has a zero-like proton adsorbed free energy in both of acidic and alkaline media, however its high cost owing to a high rarity of Pt becomes the research gap of HER catalyst. As a substitution of Pt based catalyst, transition metal phosphide (TMP) has received a lot of attention among the various non-noble metal based catalyst. Among them, nickel phosphide (Ni-P) is evaluated as the most suitable catalyst for HER due to the high catalytic activity and practical usefulness. The nickel (Ni) has lower electronegativity than phosphorus (P), and the electron transfers from the Ni to P. In other words, a proton and hydride adsorbed at the negatively charged P and positively charged Ni, respectively. Because homogeneous Ni metal has a lower kinetic of proton desorption than adsorption, the higher interaction between adsorbed proton and hydride increases the kinetic of not only desorption step but also overall HER. However, in conventional fabrication methods of Ni-P such as hydrothermal and electroplating, it is difficult to control the ratio of Ni and P, which might maximize the kinetics and moreover, stability.In this context, we suggest a surficial engineering process to control the ratio between Ni and P after the electroplating of Ni-P compound on carbon fiber paper (CFP) for the efficient HER catalyst in both of acidic and alkaline media. Because ‘isolated Ni’ which has a low bonding with P has different redox potential with Ni-P, the surficial engineering is designed as a dealloying cycle of metal alloy to selectively remove the isolated Ni. As a result, The Ni-P/CFPx10 and Ni-P/CFPx20 (10, 20 times dealloying-cycled Ni-P/CFP catalyst) catalysts show higher P content of 29.6 and 36.5 at% on the surface (24.9 at% before dealloying treatment). Furthermore, the surficial engineering arouses the recrystallization of Ni-P compound, thus the permeated amount of P increases according to the number of surficial engineering cycle. In particular, the Ni-P/CFPx20 and Ni-P/CFPx10 catalysts shows the 55 mV and 58 mV lower overpotential at -10 mA cm-2 the pristine Ni-P/CFP catalyst (179 mV for acidic HER and 247 mV for alkaline HER) in acidic and alkaline HER, respectively. Figure 1

Preparation of aurum chloride complex and its use for industrial acetylene hydration catalyst process

The use of a modern homogeneous metal complex catalyst for the hydration of acetylenes is being investigated. The process is relevant both for the industry of basic organic synthesis and for the perfume industry. The analysis of existing processes used in industry for the production of acetaldehyde was carried out. Significant shortcomings of existing processes are revealed: low environmental friendliness and high energy consumption. To solve this problem, the reaction of hydration of an acetylene compound was studied using a modern homogeneous catalyst based on gold, which is not toxic. The study was conducted by selecting aliquots during the reaction. Using the 1H NMR spectroscopy method, the conversion values of phenylacetylene were calculated for the time values corresponding to the moments of aliquot sampling. The reaction order with respect to phenylacetylene was calculated and the reaction constant under the reaction conditions was calculated. When reacting in the presence of the proposed catalyst, a conversion of phenylacetylene of 86.96 % is achieved in 3 hours. The data obtained provide grounds for carrying out the process of catalytic hydration of acetylenes, namely phenylacetylene, with the production of acetophenone, which is important for use in the perfume industry. The data obtained can be applied to the process of hydration of acetylene with the formation of acetaldehyde, which is widely used in the industry of basic organic synthesis. For the process of catalytic hydration of acetylene compounds, a hardware design is proposed, a gas-liquid reactor with a changing hydrodynamic situation, which, together with the product separation column, is combined into a single installation. Using an optimized method, a catalyst based on gold chloride was synthesized from a gold alloy.

N-Heterocyclic Carbene-Stabilized Gold Nanoclusters with Organometallic Motifs for Promoting Catalysis.

The complexity of heterogeneous metal catalysts makes it challenging to gain insights into their catalytic mechanisms. Thus, there exists a huge gap between heterogeneous catalysis and organometallic catalysis. With the success in the preparation of highly robust atomically precise metal nanocluster catalysts (i.e., [Au16(NHC-1)5(PA)3Br2]3+ and [Au17(NHC-1)4(PA)4Br4]+, where NHC-1 is a bidentate NHC ligand, and PA is phenylacetylide) with surface organometallic motifs anchored on the metallic core, we demonstrate in this work how the metallic core works synergistically with the surface organometallic motifs to enhance the catalysis. More importantly, the discovery allows the development of highly stable and recyclable heterogeneous metal catalysts to achieve efficient hydroamination of alkynes with an extremely low catalyst dosage (0.002 mol %), helping bridge the gap between heterogeneous and homogeneous metal catalysis. The surface modification of metal nanocatalysts with organometallic motifs provides a new design principle of metal catalysts with enhanced catalysis.

Metallicity of Galactic RR Lyrae from Optical and Infrared Light Curves. II. Period–Fourier–Metallicity Relations for First Overtone RR Lyrae

We present new period-ϕ 31-[Fe/H] relations for first-overtone RRL stars (RRc), calibrated over a broad range of metallicities (−2.5 ≲ [Fe/H] ≲ 0.0) using the largest currently available set of Galactic halo field RRL with homogeneous spectroscopic metallicities. Our relations are defined in the optical (ASAS-SN V band) and, inaugurally, in the infrared (WISE W1 and W2 bands). Our V-band relation can reproduce individual RRc spectroscopic metallicities with a dispersion of 0.30 dex over the entire metallicity range of our calibrator sample (an rms smaller than what we found for other relations in literature including nonlinear terms). Our infrared relation has a similar dispersion in the low- and intermediate-metallicity range ([Fe/H] ≲ −0.5), but tends to underestimate the [Fe/H] abundance around solar metallicity. We tested our relations by measuring both the metallicity of the Sculptor dSph and a sample of Galactic globular clusters, rich in both RRc and RRab stars. The average metallicity we obtain for the combined RRL sample in each cluster is within ±0.08 dex of their spectroscopic metallicities. The infrared and optical relations presented in this work will enable deriving reliable photometric RRL metallicities in conditions where spectroscopic measurements are not feasible; e.g., in distant galaxies or reddened regions (observed with upcoming Extremely Large Telescopes and the James Webb Space Telescope), or in the large sample of new RRL that will be discovered in large-area time-domain photometric surveys (such as the LSST and the Roman space telescope).

Investigation of surface integrity transition of SiCp/Al composites based on specific cutting energy during ultrasonic elliptical vibration assisted cutting

Different from brittle materials or homogeneous metal materials, there is no obvious characteristic of brittle removal or plastic removal in machining of particle reinforced metal matrix composites (MMCs). In the present work, we investigate the surface integrity transition of SiCp/Al composites during ultrasonic elliptical vibration-assisted cutting (UEVC). The machined surface is divided into two parts: plastic deformation of metal matrix and defects caused by particle deformation. A specific-cutting-energy-based criterion based on the relationship between plastic deformation and defects formation, is established to characterize the surface integrity transition of SiCp/Al composites quantitatively. The effectiveness of the critical cutting parameter is verified by systematic experiments. Experimental results show that the surface integrity transition of SiCp/Al composites is mainly affected by processing method and cutting speed. When the scratching speed increases from 100 mm/min to 200 mm/min, the main part of machined surface changes from defects to plastic deformation accordingly in UEVC. The ductile surface of SiCp/Al composites can be obtained when the cutting speed, cutting depth and feed rate are 100 mm/min, 0.01 mm and 0.02 mm/rev, respectively. According to the experimental results, particle partial fracture, debonding and micro-deflection dominate particle removal process in UEVC, which is also the main reason why UEVC can improve the machinability of SiCp/Al composites.

Exporting Homogeneous Transition Metal Catalysts to Biological Habitats.

The possibility of performing designed transition‐metal catalyzed reactions in biological and living contexts can open unprecedented opportunities to interrogate and interfere with biology. However, the task is far from obvious, in part because of the presumed incompatibly between organometallic chemistry and complex aqueous environments. Nonetheless, in the past decade there has been a steady progress in this research area, and several transition‐metal (TM)‐catalyzed bioorthogonal and biocompatible reactions have been developed. These reactions encompass a wide range of mechanistic profiles, which are very different from those used by natural metalloenzymes. Herein we present a summary of the latest progress in the field of TM‐catalyzed bioorthogonal reactions, with a special focus on those triggered by activation of multiple carbon‐carbon bonds.