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The mechanism of decarboxylative allylation of amino esters via dual photoredox and palladium catalysis has been explored with DFT calculations, which reveal the cooperation of Pd catalysis, photocatalysis and substrate via single electron transfer.

Mechanistic studies disclose that Ni-catalysed hydroarylation of 1,3-dienes occurs via concerted hydronickelation, transmetalation and reductive elimination to give the product. Ligand–substrate interactions were analyzed to reveal the selectivity.

Highly selective assembly of 2,3-fused indolizines was achieved via a cascade allylation/Friedel–Crafts type reaction with Cu/Ir catalysis. This protocol furnishes a stereodivergent synthesis of chiral indolizines bearing three stereogenic centers with excellent results.

Comprehensive computational studies were carried out to explore the mechanisms of enantioselective Cu/Pd and stereodivergent Cu/Ir dual-catalytic syntheses of α,α-disubstituted α-amino acids (α-AAs). A chiral copper azomethine ylide undergoes facile α-allylation with racemic π-allylpalladium species or stereopure π-allyliridium complex to stereoconvergently or stereodivergently furnish single/double stereocenters, respectively. Stereoselectivity at the α-center is controlled by the facial selectivity of α-allylation with respect to the prochiral nucleophile. Despite apparently similar transition-state assemblies, computational models and distortion/interaction analyses disclose versatile modes of stereoinduction wherein the copper azomethine ylide species can face-selectively intercept metal-π-allyl intermediates utilizing attractive dispersion interactions and/or sterically caused distortions. Generation of the β-stereocenter in the Cu/Ir system relies on a stereospecifically generated allyliridium complex and electronically controlled branched-to-linear selectivity, while the dual Cu/Pd system yields a linear monochiral product due to steric factors and π-π stacking interactions. The studies demonstrate on a molecular level how ligand-encoded chiral information is transferred to the α-/β-sites of the resulting α-AAs and how the mode of regio-/stereoselection is altered by differences in transition-metal-stabilized coupling partners. To facilitate studies of stereoselective catalysis, a suite of analytical tools to extract controlling factors for asymmetric induction is demonstrated.

Aliphatic aldehydes are among the most common structural units in organic and medicinal chemistry research. Direct C–H functionalization has enabled efficient and site-selective derivatization of aliphatic aldehydes.

A stereodivergent synthesis of azepino[3,4,5-cd]-indoles bearing three stereogenic centers was established via synergistic dual-metal catalysis followed by acid-promoted epimerization, and up to all eight stereoisomers could be predictably achieved.

A catalytic system combining 2-aminothiazole and borane efficiently catalyzes a four-component tandem reductive coupling of primary amines, carbonyl compounds, boranes, and CO2 (1 atm) and a broad range of functionalized tertiary N-methylamines are synthesized.

Combined theoretical and experimental studies have explained the mechanism of Pd-catalyzed δ-C(sp3)−H arylation of primary amines. Instead of the monomeric Pd mechanism, our research unveils that all steps including C–H activation, oxidative addition, and reductive elimination take place via the heterodimeric Pd–Ag intermediates and transition states. Experimentally, the active heterodimeric Pd–Ag species were detected by mass spectrometry, which further confirms the proposed heterodimeric mechanism. Insight gained through this study reveals the synergistic manner of palladium catalysis and silver(I) additives in native NH2-directed C‒H activation and C–C coupling reactions.

We describe cooperative bimetallic catalysis that enables regio-/stereodivergent asymmetric α-allylations of aldimine esters. By employing Et

Electrochemical CO2 reduction reaction (CO2RR) is an attractive pathway for closing the anthropogenic carbon cycle and storing intermittent renewable energy by converting CO2 to valuable chemicals and fuels. The production of highly reduced carbon compounds beyond CO and formate, such as hydrocarbon and oxygenate products with higher energy density, is particularly desirable for practical applications. However, the productivity towards highly reduced chemicals is typically limited by high overpotential and poor selectivity due to the multiple electron-proton transfer steps. Tandem catalysis, which is extensively utilized by nature for producing biological macromolecules with multiple enzymes via coupled reaction steps, represents a promising strategy for enhancing the CO2RR performance. Improving the efficiency of CO2RR via tandem catalysis has recently emerged as an exciting research frontier and achieved significant advances. Here we describe the general principles and also considerations for designing tandem catalysis for CO2RR. Recent advances in constructing tandem catalysts, mainly including bimetallic alloy nanostructures, bimetallic heterostructures, bimetallic core-shell nanostructures, bimetallic mixture catalysts, metal-metal organic framework (MOF) and metal-metallic complexes, metal-nonmetal hybrid nanomaterials and copper-free hybrid nanomaterials for boosting the CO2RR performance are systematically summarized. The study of tandem catalysis for CO2RR is still at the early stage, and future research challenges and opportunities are also discussed.

The σ-dimer of a kinetically protected olympicenyl radical, which evaded the experimental detection, was revealed by conversion into biolympicenylidene with E-configuration in a regioselective manner. The complicated stereochemistry and energetics of the σ-dimers derived from C2v symmetry and uneven spin distribution of the olympicenyl radical were revealed by the theoretical calculations, and the energetic preference of π-dimer over σ-dimer by a minute gap was disclosed. The E-biolympicenylidene, a polycyclic ene structure previously considered as reactive intermediate in the phenalenyl radical system, exhibited exceptional stability, which allowed for a detailed investigation on its singlet diradical character and physical properties by means of X-ray crystallography, UV-vis-NIR absorption/emission spectroscopy and cyclic voltammetry, and assisted by theoretical calculations. The E-biolympicenylidene showed high resistance towards both thermal and photochemical ring-cyclization reactions, which was attributed to high activation energies for the rate-determining electrocyclization operated on both disrotatory and conrotatory mode, as well as a small spin density at the bonding sites for the radical-radical coupling process.

Dimeric cycloparaphenylene (CPP) architectures with well-defined flipping motion are constructed taking advantage of an efficient cyclocondensation reaction. Variable-temperature nuclear magnetic resonance (VT-NMR) analyses and theoretical calculations indicate rapid interconversion of cis and trans conformers at room temperature, while energetically favorable trans conformer exists at low temperature with the metastable cis conformer hidden. The trihexylsilylethynyl-substituted dimer exhibits bright emission in solution at 616 nm with quantum yield up to 80 %, representing the brightest CPP-based emitter beyond 600 nm. A 1:2 host-guest complex of the dimer and C60 is established with negative cooperativity, demonstrating the first example of 1:2 complex from CPP derivatives.

Two-dimensional (2D) cocrystals open a new way to get 2D functional materials via crystal engineering instead of molecular engineering. Here, large-area 2D cocrystals with length reaching several millimeters with strong near-infrared (NIR) absorption have been successfully designed and prepared. Driven by the intermolecular charge-transfer (CT) interactions, zinc tetraphenylporphyrin (donor) and C 60 (acceptor) self-assemble into a NIR cocrystals with absorption wavelength up to 1080 nm. By tailoring the growth solvents and processes, the cocrystal morphologies can be tuned from 1D nanowires, 2D nanosheets to large-area 2D cocrystal films with length reaching several millimeters. Impressively, due to the highly ordered donor-acceptor arrangement, the CT absorption in the 2D cocrystals is significantly enhanced and becomes comparable to singlet absorption. The uniform 2D cocrystals, with enhanced CT absorption in the NIR region, displays a high responsivity of 2424 mA/W to NIR light and a fast response time of 0.6 s. The excellent device performance can be attributed to the generation of long-lived free charge carriers as revealed by transient absorption spectroscopy and the optimization of device configuration. This work shows an example of controlled growth of 2D cocrystals for broadband photodetectors, which reveals the brilliant future of cocrystal films for high-performance electronics and paves their way towards large-scale, integrated, flexible, practical applications.

The mechanism and origins of ligand-controlled stereoselectivity of dirhodium (Rh2L4, L = OAc, S-tertPTTL)-catalysed intramolecular aliphatic C(sp3)–H aminations have been explored using DFT calculations. Both catalytic cycles occur via the formation of Rh2 = nitrene radical species, intramolecular H-abstraction and radical rebound. The origins of diastereoselectivity are revealed via distortion/interaction and noncovalent interaction analysis.

Mechanistic studies reveal that Pd-catalyzed C(sp3)–H arylation of thioethers with silver(I) additives takes place via C(sp3)–H activation, oxidative addition and reductive elimination, wherein all steps proceed via the heterodimeric Pd–Ag pathway. Besides, the active heterodimeric Pd–Ag species are detected by mass spectrometry via control experiments.

DFT studies reveal that Ni-catalysed redox-relay hydroarylation of alkenes occurs via concerted hydronickelation, iterative β-H elimination/migratory insertion and reductive elimination to yield the α-substituted product. The driving force for the redox-relay migratory hydroarylation arises from the stability of the LArNi(II)CHPhPr intermediate, which only allows its C-C elimination pathway to be opened up.

Density functional theory calculations have revealed the mechanism and origin of regio- and stereoselectivity in [2,3]-sigmatropic rearrangements of diazoesters with allylic iodides/sulfides via ch...

The mechanism of nickel-catalyzed hydroarylation of styrenes has been explored with density functional theory. Instead of the stepwise pathway via a Ni(II)-H species, computational results unveil that the concerted RO-H oxidative addition/olefin insertion takes place kinetically favorable to generate the alkylnickel(II) species, which further undergoes transmetalation and reductive elimination to yield the hydroarylated product. The origins of regio- and stereoselectivity were revealed via analyzing the electronic and steric effects of the key transition states.

The utilization of diphenyl sulfoxides as versatile electrophilic coupling partners for the Suzuki–Miyaura reaction via C–S bond cleavage was successfully developed under palladium-N-heterocyclic carbene catalysis. The reactions showed good functional group compatibility, proceeded well under mild conditions, and provided biaryls in yields of up to 96%. A wide range of useful functional groups, such as fluoro, chloro, ether, hydroxyl, amide, cyano, keto, trimethylsilyl (TMS), and ester were tolerated under the reaction conditions; however, the use of phenylboronic anhydride and arylboronic acid pinacol esters generally would lead low yields. Good regioselectivity for the electron-poor phenyl group was achieved when unsymmetrical diphenyl sulfoxides were used. The protocol is applicable at the gram scale even with half the amount of catalyst. Density functional theory calculations were performed to investigate the reaction mechanism, indicating that the reaction occurred through oxidative addition, transmetalation, and reductive elimination to provide the final coupling product.

The mechanism of palladium-catalyzed γ-C(sp3)-H arylation of aliphatic alcohols has been explored with density functional theory. In contrast to the common "inner-sphere" C-H activation mode that favors five-membered over six-membered cyclopalladation, the computational results reveal that the "outer-sphere" C-H activation pathway assisted by added base (e.g., Li2CO3) is kinetically favorable and supports six-membered over five-membered cyclopalladation to yield the experimental γ-C(sp3)-H arylation product. Distortion/interaction analysis reveals the origins of the unconventional γ site selectivity.

Due to the existence of vertical velocity in diving-squint synthetic aperture radar (SAR) imaging, the azimuth-shift invariance along the horizontal direction is not satisfied. This will lead to a big approximation error and influence the imaging results when the existing imaging processing methods are directly applied. In order to solve these problems, an equivalent model is first introduced to describe the motion characteristic in the diving-squint mode. By adopting this approach, the diving-squint SAR imaging can be treated as the conventional one, i.e., the height remains unchanged, with the azimuth-shift invariance satisfied along the flight direction. Based on the equivalent model, a two-step processing method for the diving-squint SAR imaging with subaperture data is proposed in this article. First, a time-scaling approach is adopted to obtain the well-focused 2-D image in the slant plane. Since the equivalent model will cause the rotation of the imaging projection plane and introduce the severe distortion in the ground imagery, a rapid geometric correction method based on inverse projection is further performed to get the ground imagery with little distortion through 2-D sinc interpolation. Simulation and real-data results validate the effectiveness of the proposed approach.

DFT study suggests that the C–H cleavage involved in the C(sp3)–H amination catalyzed by manganese perchlorophthalocyanine complex [MnIII(ClPc)]+ proceeds via hydride transfer (HYT), instead of hyd...

Herein, two new poly(phenylene vinylene)-derivated semiconductors, poly(benzopyrrolone-p-phenylene-vinylene) (PBPPV) and poly(benzopyrrolone-di-p-phenylene-vinylene) (diPBPPV), are designed and synthesized with lactam groups as the electron-deficient and lateral extending units and phenylethylene as the emissive element for achieving integrated optoelectronic properties. Comprehensive characterization demonstrates that both PBPPV and diPBPPV are red-emissive materials with a photoluminescent quantum yield (PLQY) of up to 7% and exhibit well-balanced ambipolar transport properties with the electron and hole mobility approaching 4.5 × 10−4 cm2 V−1 s−1 and 3.0 × 10−4 cm2 V−1 s−1, respectively. This work provides valuable guidelines for further improvement of integrated optoelectronic conjugated polymers by rational molecular design.

Solid-state high-power heat output at a relatively low temperature is a core problem for photo thermal batteries (PTB) films because of the fundamental contradiction between fast heat release and low-rate isomerization. To overcome this problem, imidazole-containing azoheteroarene (i-Azo-h) is introduced into a graphene-templated assembly for low-temperature time-resolved heat release. Intramolecular pull-push electronic interaction of i-Azo-h in the assembly film results in high-rate and high-degree trans-cis isomerization compared with azobenzene. The uniform i-Azo-h/graphene PTB film reaches very high power density (2380 W kg−1) and high energy density (105 Wh kg−1). A “tortoise”-like integrated system is designed as a high-power photo-heat source to realize a reversible and controllable temperature rise up to 3.3–4.1 °C on the “back” with a temperature gradient of the “leg.” Results show that heat release rate at 60 °C and under room-temperature green-light irradiation at 535 nm are higher than those at 45 °C, indicating controllability in time-resolved temperature rise. Based on these results, a thermally controllable dual encoding/reading strategy based on reversible time-resolved thermochromic-patterned display is developed for the first time. Dual encoding/reading information (response time or a specific pattern) can be selectively changed by optimizing isomerization degree or stimulus.

To reveal the influence of synergistic effect of non-covalent forces on the FET performance, two highly symmetrical “H”-shaped heteroarene derivatives anthra[2,1-b:3,4-b′:6,5-b′′:7,8-b′′′]tetra(benzothiophene) (ATBT) and anthra[2,1-b:3,4-b′:6,5-b′′:7,8-b′′′]tetra(benzofuran) (ATBF) as novel two-dimensional (2D) organic semiconductor materials were synthesized. The thermal, optical and electrochemical properties of ATBT and ATBF were investigated and high stability was confirmed. Single crystal XRD of ATBT confirmed the close π–π stacking due to the “wider” π-conjugation framework and four S atoms sited on both sides of each molecule could produce eight S⋯S contacts with neighbouring molecules. Mobility of up to 15.6 cm2 V−1 s−1 could be achieved for the single-crystalline field effect transistor, which was fabricated by the ‘two-dimensional organic-ribbon mask’ technique based on the individual ATBT microribbon. The strong anisotropy along different crystal axes is consistent with the molecular arrangement, which was evidenced by XRD, TEM and corresponding selected-area electron diffraction pattern. Moreover, the analogue ATBF shows lower FET performance due to lack of S⋯S contacts in comparison to that of ATBT, which reflects that the synergistic effect of non-covalent forces has an important influence on the molecular aggregation and electrical properties.

The development of enantioselective annulation reactions using readily available substrates for the construction of structurally and stereochemically diverse heterocycles is a compelling topic in diversity-oriented synthesis. Herein, we report efficient catalytic asymmetric formal 1,3-dipolar (3 + 4) cycloadditions of azomethine ylides with 4-indolyl allylic carbonates for the construction of azepino[3,4,5

Enzymatic reaction, as an environmentally friendly approach, has made great progress producing commodity chemicals comparing to the conventional metallo/organo catalysis. However, the reaction compatibility is not satisfactory. The development of biomimetic catalysis balancing both strategies for the green and broad application in synthesis is desirable. Here, we report the design and synthesis of a chiral diamine catalyst fulfilling this requirement. Asymmetric addition reactions using this ligand in water were demonstrated and the corresponding products were produced in excellent yields and enantiomeric ratios. This pluripotent ligand has also shown good reactivity/enantioselectivity on a number of representative reactions in both green and organic solvents. We anticipate that the ligand would allow further development of other catalysts for important yet challenging green stereoselective transformations.

The traditional synthetic aperture radar (SAR) platform positioning methods based on the range-Doppler domain data, velocity and altitude information of the platform exist a large approximation error, which will not satisfy the requirement of accurate navigation. Additionally, the traditional positioning methods for solving non-linear equations are challenging due to the risk of falling into local optimal solution. In order to solve these problems, a new robust SAR platform positioning method based on the improved Gauss–Newton–genetic hybrid (GNGH) algorithm is proposed in this study. First, the position information of multi-feature points in geographic and imaging coordinate systems is acquired by adopting the image matching. Furthermore, the coordinate transformation is introduced to realise the uniform of feature point coordinates between the different coordinate systems. Finally, the accurate position of the platform is calculated through introducing GNGH algorithm to solve the non-linear equations constructed by the corresponding slant range information. So the trajectory deviation can be corrected effectively. Moreover, the proposed method can reduce the computation load and positioning error dramatically. The effectiveness of the proposed approach is confirmed and demonstrated via simulation and experimental results.

DFT calculations have been combined with experiments to study the mechanism of γ-C(sp3)–H arylation of aliphatic amines promoted by palladium–glyoxylic acid cooperative catalysis, with a focus on the role of silver(I) additives. Glyoxylic acid (the cocatalyst) uses its aldehyde functionality to react with the amine substrate to form an iminoacetic acid. This acid acts as a transient directing reagent and metathesizes with Pd(OAc)2 (the precatalyst) to give a Pd(II)–diiminoacetate five-membered chelate, which has been shown computationally as the catalyst resting state and which has been experimentally synthesized and characterized. C(sp3)–H activation from the Pd(II)–diiminoacetate complex or its mononuclear derivatives would face a high kinetic barrier (>30 kcal/mol) arising mainly from breaking a stable five-membered N,O-chelate ring. The crucial role of the silver(I) carboxylate additive is in reacting with the Pd(II)–diiminoacetate complex to provide a heterodimeric Pd(II)–Ag(I) complex supported by b...

Deformation-controlled solar thermal storage and release are important for thermal management of dynamic systems. However, few researchers have examined cyclic solid-state solar thermal utilization...

A protocol for C(sp)–C(sp2) bond formation via the Sonogashira coupling reaction involving C–N bond cleavage with aryltrimethylammonium triflate as an electrophilic coupling partner is described in...

The Mn-catalyzed C-H functionalization of indoles with allenes developed by Rueping and co-workers provides an efficient access to various alkenylated indoles and substituted pyrroloindolones. Herein, we present a systematic computational study to understand the mechanism and origins of substrate-controlled chemoselectivity of the C-H functionalization reactions (hydroarylation vs cascade cyclization). For the disubstituted allene system, the computed mechanism consists of three main phases: C-H activation, allene migratory insertion, and protonation giving the hydroarylation product. All of these steps are feasible, in agreement with the good yield under the mild experimental conditions. On the other hand, for the trisubstituted allene system, hydroarylation is suppressed due to the higher energy barrier for the protonation step arising from the disfavored ligand-substrate steric repulsions between the carboxide ligand and the substituent group in the allene substrate; our computational results demonstrate that, after the allene insertion leading to a seven-membered cyclometalated intermediate, it undergoes a reaction pathway involving sequential "ketone to enol" isomerization, a 1,4-heteroaryl shift, and β-methoxyl elimination giving the pyrroloindolone product. In contrast, this isomerization → heteroaryl shift → β-methoxyl elimination process is unworkable in the disubstituted allene system, because the protonation step takes place more favorably owing to the lack of ligand-substrate steric interactions. The findings taken together give an insight into the role of the ligand-substrate interactions in directing the competitive pathways and differentiating the energies of key transition states by steric repulsions.

Iron-catalyzed direct amination of aliphatic C(sp3)–H bonds developed by Betley et al. (Science, 2013, 340, 591–595) is an efficient synthetic method to access a range of substituted pyrrolidines. Herein, we conducted density functional theory (DFT) calculations to explore the mechanism and origins of regioselectivity of this remarkable C(sp3)−H amination using an iron-dipyrrinato catalyst. Computational results show that iron-catalyzed C(sp3)–H amination occurs via the following phases: (a) ligand–substrate exchange offering the active Fe(II) catalyst; (b) oxidation of the Fe(II) catalyst to an Fe(III)-nitrene radical species using the alkyl azide substrate with the release of N2 molecules; (c) intramolecular H-abstraction (C⋯H⋯N) affording an alkyl radical and an Fe(III)-iminyl radical; and (d) radical rebound leading to a N-heterocyclic compound, which reacts with Boc2O to avoid product inhibition via a highly exergonic reaction affording an N-protected amine and regenerates the active Fe(II) catalyst by coordination with another alkyl azide substrate. Owing to the effortless nature of the radical rebound process, the calculations reveal that the H-abstraction step determines the regioselectivity of amination, with which arising mainly from a combination of radical stability and ring strain. The results demonstrate rich experimental–theoretical synergy and provide useful insights for further development of site-selective C–H functionalization reactions.

Density functional theory calculations have revealed the mechanism and origins of the reactivity and regioselectivity of the Cp*Ir(III)/Cp*Rh(III)-catalyzed allylic C–H amidation of alkenes and dioxazolones. Generally, the catalytic cycle consists of alkene coordination, C(sp3)−H activation, dioxazolone oxidative addition, reductive elimination and proto-demetallation to give the final amidation product. The C–H activation is found to be the rate-determining step, and it controls the reactivity of the reaction. For the Cp*Ir(III)-catalyzed system, the C–H activation undergoes an Ir(III)-assisted proton transfer process with a low energy barrier, elucidating its high reactivity. In contrast, the C–H activation step is more like a direct deprotonation in the Cp*Rh(III)-catalyzed system, which is responsible for its higher barrier and lower reactivity. The branched-selectivity arises from the electronic effect of the alkyl group on the charge distribution over the allylic moiety. Herein, iridium(V) polarizes the allylic group greater than that of the rhodium(V) system, which accounts for its good regioselectivity. The mechanistic insights will be useful for the further development of transition metal-catalyzed selective C–H amination reactions.

The classical synthesis of quinoids, which involves Takahashi coupling and subsequent oxidation, often gives only low to medium yields. Herein, we disclose the keto–enol-tautomerism-assisted spontaneous air oxidation of the coupling products to quinoids. This allows for the synthesis of various indandione-terminated quinoids in high isolated yields (85–95%). The origin of the high yield and the mechanism of the spontaneous air oxidation were ascertained by experiments and theoretical calculations. All the quinoidal compounds displayed unipolar n-type transport behavior, and single crystal field-effect transistors based on the micro-wires of a representative quinoid delivered an electron mobility of up to 0.53 cm2 V−1 s−1, showing the potential of this type of quinoid as an organic semiconductor., Facilitated by the highly efficient Pd-catalyzed coupling and keto–enol-tautomerism-assisted spontaneous air oxidation, various indandione-terminated quinoidal compounds have been synthesized in isolated yields up to 95%.

An olympicenyl radical, a spin 1/2 hydrocarbon radical with C2v symmetry and uneven spin distribution, remains elusive despite the considerable theoretical research interest. Herein, we report syntheses of two air-stable olympicenyl radical derivatives, OR1 and OR2, with half-life times (τ1/2) in air-saturated solution of 7 days and 34 days. The high stability was ascribed to kinetic blocking of reactive sites with high spin densities. X-ray crystallographic analysis revealed unique 20-center-2-electron head-to-tail π-dimer structures with intermolecular distances shorter than the sum of van der Waals radius of carbon. The ground state of the π-dimers was found to be singlet, with singlet-triplet energy gaps estimated to be -2.34 kcal/mol and -3.28 kcal/mol for OR1 and OR2, respectively, by variable-temperature electron spin resonance (ESR) spectroscopy. The monomeric radical species were in equilibrium with the π-dimer in solution, and the optical and electrochemical properties of the monomers and π-dimers in solution were investigated by UV-vis-NIR spectroscopy and cyclic voltammetry, revealing a concentration-dependent nature. Theoretical calculations illustrated that upon formation of a π-dimer the local aromaticity of each monomer was enhanced, and spatial ring current between the monomers was present, which resulted in an increment of aromaticity of the interior of the π-dimer.

The mechanism of palladium-catalyzed γ-C(sp

DFT study suggests that the C-H cleavage involved in the C(sp