Non classé – ChemDigest

Photoinduced Metal‐Free Decarboxylative Transformations: Rapid Access to Amines, Alkyl Halides, and Olefins

Par admin / 23 mars 2023 23 mars 2023 / Non classé

Herein, we described a versatile photocatalytic strategy for the decarboxylative transformations of redox-active esters (RAE) to a variety of alkyl halides, amines, and olefins in the presence of ⁿBu₄NI in a single-step. It is a straightforward method which is applied to the functionalization of a series of primary, secondary, and tertiary aliphatic carboxylic acid derivatives and complex natural products. Mechanistically, a charge transfer complex (CTC) was formed through non-covalent interaction between RAE and ⁿBu₄NI. Upon photoexcitation, the ammonia salt acted as both an efficient electron donor and an iodine source for radical recombination. The mild reaction condition allows this method can be applied for modification of complex natural products and versatile follow-up transformations.

Abstract

Herein, we report an efficient photocatalytic strategy for the decarboxylative transformations of redox-active esters to construct C=C, C(sp³)−N, and C(sp³)−X bonds in a single-step. This operationally simple method provides a straightforward access to a variety of protected alkyl amines, alkyl halides and olefins under mild conditions in the absence of metals and photocatalysts. The method can successfully be applied to primary, secondary, and tertiary aliphatic carboxylic acid derivatives. Mechanistic studies indicate that the charge transfer complex (CTC) was formed by ⁿBu₄NI with redox-active esters, in which the ⁿBu₄NI acted as both an iodine source and an efficient electron donor.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Jia‐jing Luo, Dong Jing, Cong Lu, Ke Zheng
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202300167

Reactions in Endohedral Functionalized Cages

Par admin / 23 mars 2023 23 mars 2023 / Non classé

Endohedral-functionalized cage compounds play an increasing role in cage chemistry. Here, the recent developments of reactions that are mediated or catalyzed by such endohedral-functionalized cages is reviewed. The article is structured according to the role that the endohedral group plays with respect to the reaction mediated or catalyzed.

Abstract

The introduction of enhanced functionalization is a key aspect in the current design of cage chemistry. At the moment, several approaches are intensively investigated. The synthesis of cage compounds that display endohedral functionalization plays a key role among them. Here, the studies of reactions that occur in endohedral-functionalized cage compounds is reviewed. After an introduction in current trends in cage-chemistry the discussion of reactions in endohedral-cage compounds is divided into three sections. These are: 1) Endohedral groups that are by themselves functional, 2) endohedral groups that can bind to a transition-metal complex and 3) endohedral groups that can bind by themselves to a metal. The article closes with an outlook on additional current developments in the field of endohedral-functionalized cage-compounds, which may contribute in the future towards reactivity in cage compounds.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Matthias Otte
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202300012

Pyridine Adducts of Tricyano‐ and Dicyanoboranes

Par admin / 23 mars 2023 23 mars 2023 / Non classé

Efficient syntheses for pyridine and 4-cyanopyridine adducts of the strong Lewis acids BH(CN)₂, B(CN)₃, and BF(CN)₂ starting from readily available hydridoborates are described. The different Lewis acidities of the three boranes have been assessed by the Gutmann-Becket method and by calculated fluoride ion affinities (FIA). In addition, the electrochemical properties of the borane adducts have been studied by cyclic voltammetry.

Abstract

Cyanoborane adducts of the Lewis acids B(CN)₃, BF(CN)₂, and BH(CN)₂ with pyridine and 4-cyanopyridine have been obtained in high yields. The syntheses were accomplished by oxidation of the readily available potassium salts of the cyano(hydrido)borate anions [BH(CN)₃]⁻ (MHB), [BFH(CN)₂]⁻ (FHB), and [BH₂(CN)₂]⁻ (DHB) with bromine in the presence of the respective pyridine derivative C₅H₅N or 4-CN-C₅H₄N as starting material. All six cyanoborane adducts have been characterized by NMR and vibrational spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The reduction of the cyanoborane adducts has been investigated by cyclic voltammetry and the Lewis acidity of the different cyanoboranes has been assessed using the Gutmann-Beckett method. Selected experimental data and trends are compared to theoretical ones, for example fluoride ion affinities (FIAs).

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Jarno Riefer, Ludwig Zapf, Raphael Wirthensohn, Philipp T. Hennig, Tatjana Ribbeck, Jan A. P. Sprenger, Nikolai V. Ignat’ev, Maik Finze
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202300031

Water‐Induced Single‐Crystal to Single‐Crystal Transformation of Ionic Hydrogen‐Bonded Organic Frameworks with Enhanced Proton Conductivity

Par admin / 23 mars 2023 23 mars 2023 / Non classé

Single crystal to single crystal transition: This study reports the synthesis of two hydrogen-bonded organic frameworks (HOFs) and the transformation of iHOF-10 to iHOF-11. The results show that water molecules induce the single crystal to single crystal transition process, as well as increase the proton conductivity.

Abstract

Two ionic hydrogen-bonded organic frameworks (iHOF-10, iHOF-11) were prepared using 1,1′-diamino-4,4′-bipyridine diiodide (Dbpy ⋅ 2I) and tetrakis(4-sulfophenyl)ethylene (H₄TPE). With increasing RH and temperature, water molecules induce single crystal to single crystal (SCSC) transformation of iHOF-10, resulting in the formation of iHOF-11. At 90 °C, 98 % RH, the proton conductivity of iHOF-11 (7.03×10⁻³ S cm⁻¹) is 2.09 times higher than iHOF-10 (3.37×10⁻³ S cm⁻¹). At 50 °C, 98 % RH, iHOF-11 (9.49×10⁻⁴ S cm⁻¹) is 19.06 times higher than iHOF-10 (4.98×10⁻⁵ S cm⁻¹). The proton conductivity shows water molecules enter the crystal and induce crystal transformation and reorganization of the hydrogen bonding structure, thus increasing the proton conductivity and stability.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Xu‐Yong Chen, Li‐Hui Cao, Yan Yang, Xiang‐Tian Bai, Fang Zhao, Xiao‐Jie Cao, Ming‐Feng Huang, Yi‐Da Gao, Dan Yang
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202300028

Oxovanadium(V)‐Catalyzed Deoxygenative Coupling Reaction of Alcohols with Trimethylsilyl Enol Ethers in the Presence of MS3A

Par admin / 23 mars 2023 23 mars 2023 / Non classé

The deoxygenative coupling reaction of allyl alcohols with trimethylsilyl enol ethers was performed by using a commercially available oxovanadium(V) catalyst, providing γ,δ-unsaturated carbonyl compounds in one-step. This catalytic system could be applied to a gram-scale catalytic synthesis of the γ,δ-unsaturated carbonyl compound and the deoxygenative coupling reaction of benzyl alcohols with trimethylsilyl enol ethers.

Abstract

Oxovanadium(V)-catalyzed deoxygenative coupling reaction of allyl alcohols with trimethylsilyl enol ethers was demonstrated to afford γ,δ-unsaturated carbonyl compounds in one-step. The catalytic deoxygenative coupling reaction of allyl alcohols proceeded smoothly with both aromatic and aliphatic trimethylsilyl enol ethers. This catalytic deoxygenative coupling system could be applied to the deoxygenative coupling reaction of benzyl alcohols with trimethylsilyl enol ethers, providing the corresponding carbonyl compounds. Furthermore, a gram-scale catalytic synthesis of the γ,δ-unsaturated carbonyl compound was successfully performed to validate the scalability of this catalytic deoxygenative coupling reaction.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Takanari Matsutani, Takashi Sakuramoto, Kento Okabayashi, Mamoru Tobisu, Toshiyuki Moriuchi
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202201410

KI‐Mediated Chlorine Gas‐Free Synthesis of 3,3‐Dichloro‐2‐oxindole Derivatives

Par admin / 23 mars 2023 23 mars 2023 / Non classé

An efficient KI-mediated chloro-oxidation of indoles was developed, using KCl/NaCl as the chlorine source and oxone as oxidant, which affording various functionalized 3,3-dichloro-2-oxindoles in moderate to excellent yields. This chlorine gas-free protocol provided a practical approach for the synthesis of a series of 3-chloro-2-oxindole derivatives.

Abstract

An efficient and environmentally friendly methodology for 3,3-dichlorination and 2-oxidation of indole derivatives is described. Using KI as promotor, MCl (M=K, Na) as chlorine source, and oxone as oxidant, the reaction proceeds smoothly affording various functionalized 3,3-dichloro-2-oxindoles in moderate to excellent yields. This strategy can also be extended to 3-substituted indoles. With a broad substrate scope, it is a practical approach to 3,3-disubstituted-2-oxindoles.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Xuejian Li, Bangzhong Wang, Dong Li, Jinfeng Zhao, Jingping Qu, Yuhan Zhou
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202201452

Construction of C2‐Spirocyclopropyl‐Indolin‐3‐Ones through Base‐Promoted [2+1] Annulation Reaction of Indolin‐3‐ones with Bromosulfonium Salts

Par admin / 23 mars 2023 23 mars 2023 / Non classé

A simple and efficient base-promoted [2+1] annulation reaction has been developed for the synthesis of the structural diversity C2-spirocyclopropyl-indolin-3-ones. This [2+1] annulation process using simple and easily prepared nucleophilic indolin-3-ones (as C1 synthons) and bromosulfonium salts (as C2 synthons) as substrates, and realized the synthesis of C2-spirocyclopropyl-indolin-3-ones with up to 99 % yield and >20 : 1 dr.

Abstract

A simple base-promoted [2+1] annulation of indolin-3-ones and bromosulfonium salts has been developed in this article. This strategy uses simple and easily prepared indolin-3-ones 1 as C1 synthons and bromosulfonium salts 2 as C2 synthons under mild reaction conditions, and 33 examples of C2-spirocyclopropyl-indolin-3-ones were obtained with up to 99 % yield and >20 : 1 dr.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Mao Zhang, Fenfen Yang, Xiang Guan, Mingshan Shuai, Qingqing Zhang, Xiaozhong Fu, Yuanyong Yang, Meng Zhou, Bin He, Yonglong Zhao
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202300159

Visible Light Promoted Iron‐Catalyzed One‐Pot Synthesis of 2‐Arylimino‐2H‐Chromenes from 2‐Hydroxybenzyl Alcohols and β‐ Ketothioamides at Room Temperature

Par admin / 23 mars 2023 23 mars 2023 / Non classé

Abstract

An efficient, environmentally benign and one-pot approach for the synthesis of 2-arylimino-2H-chromenes from 2-hydroxybenzyl alcohols and β-ketothioamides at room temperature under visible light has been developed. The reported reaction conditions were favorable for a wide range of β-ketothioamides afforded good to excellent yields of the respective products. The low cost and air stable Knölker iron catalyst has been employed for the dehydrogenation of 2-hydroxybenzyl alcohols under photolysis that would usually require a higher temperature.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Mohd Waheed, Meshari A. Alsharif, Mohammed Issa Alahmdi, Sayeed Mukhtar, Humaira Parveen
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202300136

Highly Selective and Practical Iron‐Catalyzed Formal Hydrogenation of Epoxides to Primary Alcohols Using Formic Acid

Par admin / 23 mars 2023 23 mars 2023 / Non classé

Highly selective and efficient synthesis of primary alcohols from epoxides could be achieved under mild conditions by iron catalysis, this process used formic acid as hydrogen source and was suitable for both alkyl- and aryl-substituted epoxides.

Abstract

A highly selective, efficient and practical method for synthesizing primary alcohols was presented. By using cheap Fe(BF₄)₂ ⋅ 6H₂O and /tris[2-(diphenylphosphino)phenyl]phosphine (L1) as catalysts with formic acid as hydrogen source, a variety of primary alcohols bearing versatile functional groups could be obtained from both alkyl- and aryl-substituted epoxides under mild conditions.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Yi‐Xuan Yao, Hong‐Wei Zhang, Chang‐Bo Lu, Hong‐Yan Shang, Yuan‐Yu Tian
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202300111

Construction of Y‐Doped BiVO4 Photocatalysts for Efficient Two‐Electron O2 Reduction to H2O2

Par admin / 23 mars 2023 23 mars 2023 / Non classé

Y doping induces the formation of monoclinic/tetragonal BiVO₄ heterojunction and improves the O₂ adsorption, which facilitates the two-electron reduction of O₂. Compared with original BiVO₄, the photocatalytic H₂O₂ production activity of Y-doped BiVO₄ is significantly increased.

Abstract

Photocatalytic hydrogen peroxide (H₂O₂) production on BiVO₄ photocatalysts using water and oxygen as raw materials is a green and sustainable process. However, the photocatalytic efficiency of pristine BiVO₄ is limited by severe charge recombination. In this work, rare earth element Yttrium (Y) doped BiVO₄ photocatalysts were fabricated by the hydrothermal method. In the photocatalytic H₂O₂ production experiment, the optimized Y-doped BiVO₄ photocatalyst produced 114 μmol g⁻¹ h⁻¹ of H₂O₂ under simulated sunlight (AM1.5) irradiation, which is four times higher than production activity of pure BiVO₄ (26 μmol g⁻¹ h⁻¹). Density functional theory (DFT) calculation revealed that Y doping can enhance oxygen adsorption on the BiVO₄ photocatalyst surface. Mechanistic investigations suggest that the doping process induces the in situ formation of monoclinic/tetragonal BiVO₄ heterojunction, which further promotes the photogenerated carriers separation efficiency.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Dujuan Dai, Xiaolei Bao, Qianqian Zhang, Zeyan Wang, Zhaoke Zheng, Yuanyuan Liu, Hefeng Cheng, Ying Dai, Baibiao Huang, Peng Wang
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202203765

Photo‐Induced In Situ Generation of Brønsted Acid for Catalytic Friedel–Crafts Alkylation of Indoles

Par admin / 23 mars 2023 23 mars 2023 / Non classé

A photo–induced indole 2–alkylation reaction using unactivated, sterically congested alkenes as the Friedel–Crafts alkylation reagent gives a variety of 2-branched alkylated indole molecules in generally good efficiencies, with a broad scope of functional groups well tolerated.

Abstract

A photo-induced indole 2-alkylation reaction was developed with unactivated stereo-congested alkenes used as the Friedel–Crafts alkylation reagent. The neutral, traceless and inexpensive perfluoroalkyl iodide C₄F₉I was used as the radical initiator in catalytic amount under irradiation by a blue LED light. Brønsted acids are in situ generated from the radical transfer reactions between the indole substrates and the perfluoroiodide catalyst. A variety of 2-branched alkylated indole molecules could be obtained from this approach in generally good efficiencies, with a broad scope of functional groups well tolerated. Mechanistic studies via both experimental and computational methods indicate that the reaction was accelerated by the protons generated from the crack of the indole-derived radical cation species.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Xuling Pan, Wei Wang, Xiuhui Gao, Gefei Hao, Tingting Li
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202203876

Nanolobatone A, An Unprecedented Diterpenoid and Related New Casbanoids from the Hainan Soft Coral Sinularia nanolobata

Par admin / 23 mars 2023 23 mars 2023 / Non classé

A novel antibacterial diterpenoid: The chemical investigation of Hainan soft coral Sinularia nanolobata, has led to the isolation and characterization of a novel antibacterial diterpenoid, Nanolobatone A, featuring an unprecedented tricyclo[10.3.0.0^1,2]pentadecane carbon skeleton, along with eight new casbane-type diterpenoids.

Abstract

Nanolobatone A, featuring an unprecedented tricyclo[10.3.0.0^1,2]pentadecane carbon skeleton, along with four new polyoxygenated and four unusual endoperoxide-bridged casbane-type diterpenoids were isolated from the Hainan soft coral Sinularia nanolobata. The structures of the new compounds were established by extensive spectroscopic analysis, X-ray diffraction analysis, and time-dependent density functional theory/electronic circular dichroism calculations. A plausible biosynthetic pathway of new isolates was proposed. Bioassays revealed that nanolobatone A showed weak antibacterial activity against the Gram-positive bacteria Streptococcus pyogenes.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Jiao Liu, Song‐Wei Li, Qing‐Min Zhao, Zai‐Yong Zhang, Li‐Gong Yao, Yu‐Cheng Gu, Le‐Fu Lan, Yue‐Wei Guo
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202300055

Chalcogen Bonding Catalysis of the Cloke‐Wilson Rearrangement

Par admin / 23 mars 2023 23 mars 2023 / Non classé

Conventionally, the Cloke-Wilson rearrangement is facilitated by strong Lewis acids, Brønsted acids and Lewis bases. Herein, a chalcogen bonding catalysis approach to the Cloke-Wilson rearrangement is established, affording dihydrofurans with moderate to good yields.

Abstract

The Cloke-Wilson rearrangement is an important method to construct heterocycles which was conventionally facilitated by strong Lewis acids, Brønsted acids and Lewis bases. A weak interaction catalysis approach to the Cloke-Wilson rearrangement remains a challenging topic and yet no example is reported. Herein, a chalcogen bonding catalysis method to achieve the Cloke-Wilson rearrangement is described that involves activation of carbonyl cyclopropanes by double Se⋅⋅⋅O interactions. This chalcogen bonding catalysis approach afforded a wide range of dihydrofurans with good yields, thus establishing an alternative strategy to catalyze the Cloke-Wilson rearrangement.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Xinglong Yuan, Lintao Bao, Zhiguo Zhao, Yao Wang
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202203822

The Tunable and Efficient Nanoporous CuAg Alloy Catalysts Toward Methanol Oxidation Reaction Synthesized by Electrochemical Dealloying of Metallic Glassy Precursors

Par admin / 23 mars 2023 23 mars 2023 / Non classé

Three-dimensional nanoporous CuAg alloy catalysts with various Cu/Ag ratios are prepared by electrochemical dealloying of metallic glassy precursors. The NPCu_1.75Ag catalyst presents the best methanol electro-oxidation properties, including a high current density and good operation stability. The designed electrodes are expected to be promising catalysts for alkaline direct methanol fuel cell applications.

Abstract

Three-dimensional (3D) nanoporous CuAg (NPCuAg) alloy catalysts with various Cu/Ag ratios are prepared by electrochemical dealloying of metallic glassy (MG) precursors. All dealloyed samples exhibit homogenous nanoporous structure and element composition distribution. After systematically evaluating their electrocatalytic performance toward MOR, it was found that the catalytic activity of the NPCuAg catalysts is enhanced along with the increase of Cu/Ag ratio, which may be attributed to the more exposed active reaction sites derived from high surface area of nanoporous structure and the optimal synergistic effect. Thus, the NPCu_1.75Ag alloy catalyst presents the best methanol electro-oxidation properties, including a high current density of 397.2 mA cm⁻² and good operation stability that retaining 84.5 % catalytic activity even after 7200 s. These results outperform most reported copper-based MOR catalysts in alkaline methanol solution. Considering these advantages, the designed electrodes are expected to be promising catalysts for alkaline DMFCs applications.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Lan Yang, Hanyu Li, Lingyi Han, Shantang Liu
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202203968

Enantioselective Transformations from Nitriles to NH2‐α‐Tertiary Amines

Par admin / 23 mars 2023 23 mars 2023 / Non classé

A new catalytic strategy from commercial nitriles to high enantioselective α-tertiary primary amines in up to 90 % yield and 95 % enantiomeric excess was developed. This approach goes through twice addition processes in one pot. Specifically, organolithium reagents were added to nitriles to form the imine intermediates in situ which were further transformed by a catalytic asymmetric addition of Cu-allyl to afford the α-tertiary homoallylic NH₂-amines.

Abstract

Organic molecules, containing one or more amine chiral centers, are very common to see in natural products and medicines. Although a large number of methods have been developed to afford enantiopure amines, most of the known approaches are limited with various reasons. For example, many methodologies start from nitrogen protected and activated substrates, which usually need multistep operations and seriously decrease the atom economy. Here we disclose a new catalytic strategy from commercial nitriles to high enantioselective α-tertiary primary amines in up to 90 % yield and 95 % enantiomeric excess. This transformation firstly undergoes an addition process of organolithium reagents to nitriles to generate the imine intermediates in situ. Subsequently, the most challenging step is by employing copper catalytic enantioselective addition of AllylBpin to the imine intermediates to form the final amines in one pot.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Qing Li, Yinrui Shi, Yina Ma, Liuyang Ding, Xiang Li, Jiuling Li, Yafei Guo, Baomin Fan
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202300451

Influence of Organic‐Cation Defects on Optoelectronic Properties of ASnI3 Perovskites A=HC(NH2)2, CH3NH3

Par admin / 23 mars 2023 23 mars 2023 / Non classé

To achieve higher power conversion efficiency for tin organic–inorganic halide perovskites the critical role of organic defects in nonradiative recombination should be better understood. Random rotation of organic cation can suppress nonradiative carrier trapping owing to organic defects in FASnI₃ [FA=HC(NH₂)₂], rendering the organic contributions for defect tolerance. In contrast, organic defects in MASnI₃ (MA=CH₃NH₃) are strong and active trapping centers.

Abstract

Tin organic–inorganic halide perovskites (tin OIHPs) possess a desirable band gap and their power conversion efficiency (PCE) has reached 14 %. A commonly held view is that the organic cations in tin OIHPs would have little impact on the optoelectronic properties. Herein, we show that the defective organic cations with randomly dynamic characteristics can have marked effect on optoelectronic properties of the tin OIHPs. Hydrogen vacancies originated from the proton dissociation from FA [HC(NH₂)₂] in FASnI₃ can induce deep transition levels in the band gap but yield relatively small nonradiative recombination coefficients of 10⁻¹⁵ cm³ s⁻¹, whereas those from MA (CH₃NH₃) in MASnI₃ can yield much larger nonradiative recombination coefficients of 10⁻¹¹ cm³ s⁻¹. Additional insight into the “defect tolerance” is gained by disentangling the correlations between dynamic rotation of organic cations and charge-carrier dynamics.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Qun Ji, Yilei Wu, Xinying Gao, Tingbo Zhang, Yipeng Zhou, Yehui Zhang, Ming‐Gang Ju, Jinlan Wang, Xiao Cheng Zeng
onlinelibrary.wiley.com/doi/10.1002/anie.202213386

Computational Evolution Of New Catalysts For The Morita–Baylis–Hillman Reaction

Par admin / 23 mars 2023 23 mars 2023 / Non classé

An efficient catalyst of the Morita–Baylis–Hillman was discovered using a graph-based genetic algorithm. The catalytic activity was experimentally verified by a kinetic study and the newly discovered catalysts outcompetes a widely used catalyst for this reaction.

Abstract

We present a de novo discovery of an efficient catalyst of the Morita–Baylis–Hillman (MBH) reaction by searching chemical space for molecules that lower the estimated barrier of the rate-determining step using a genetic algorithm (GA) starting from randomly selected tertiary amines. We identify 435 candidates, virtually all of which contain an azetidine N as the catalytically active site, which is discovered by the GA. Two molecules are selected for further study based on their predicted synthetic accessibility and have predicted rate-determining barriers that are lower than that of a known catalyst. Azetidines have not been used as catalysts for the MBH reaction. One suggested azetidine is successfully synthesized and showed an eightfold increase in activity over a commonly used catalyst. We believe this is the first experimentally verified de novo discovery of an efficient catalyst using a generative model.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Julius Seumer, Jonathan Kirschner Solberg Hansen, Mogens Brøndsted Nielsen, Jan H. Jensen
onlinelibrary.wiley.com/doi/10.1002/anie.202218565

Practical and General Alcohol Deoxygenation Protocol

Par admin / 23 mars 2023 23 mars 2023 / Non classé

A new protocol for alcohol deoxygenation that functions across a wide range of alcohol structures is reported. This approach combines the reductive potency of carbon dioxide radical anion with acidic additives to promote the kinetically slow C(sp³)−O bond cleavage.

Abstract

Herein, we describe a practical protocol for the removal of alcohol functional groups through reductive cleavage of their benzoate ester analogs. This transformation requires a strong single electron transfer (SET) reductant and a means to accelerate slow fragmentation following substrate reduction. To accomplish this, we developed a photocatalytic system that generates a potent reductant from formate salts alongside Brønsted or Lewis acids that promote fragmentation of the reduced intermediate. This deoxygenation procedure is effective across structurally and electronically diverse alcohols and enables a variety of difficult net transformations. This protocol requires no precautions to exclude air or moisture and remains efficient on multigram scale. Finally, the system can be adapted to a one-pot benzoylation-deoxygenation sequence to enable direct alcohol deletion. Mechanistic studies validate that the role of acidic additives is to promote the key C(sp³)−O bond fragmentation step.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Oliver P. Williams, Alyah F. Chmiel, Myriam Mikhael, Desiree M. Bates, Charles S. Yeung, Zachary K. Wickens
onlinelibrary.wiley.com/doi/10.1002/anie.202300178

Solid‐Adsorbed Polymer‐Electrolyte Interphases for Stabilizing Metal Anodes in Aqueous Zn and Non‐Aqueous Li Batteries

Par admin / 23 mars 2023 23 mars 2023 / Non classé

The optimized PEG adsorption interphases realize highly reversible Zn/Li anodes. The organic/inorganic SEI layer induced by the adsorbed PEG interphases plays a key role in the stability of the metal anode and the low N/P ratio full cells.

Abstract

Polymers are known to adsorb spontaneously from liquid solutions in contact with high-energy substrates to form configurationally complex, but robust phases that often exhibit higher durability than might be expected from the individual physical bonds formed with the substrate. Rational control of the physical, chemical, and transport properties of such interphases has emerged as a fundamental opportunity for scientific and technological advances in energy storage technology but requires in-depth understanding of the conformation states and electrochemical effect of the adsorbed polymers. Here, we analyze the interfacial adsorption of oligomeric polyethylene glycol (PEG) chains of moderate sizes dissolved in protic and aprotic liquid electrolytes and find that there is an optimum polymer molecular weight of approximately 400 Da at which the highest columbic efficiency is achieved for both Zn and Li deposition. These findings point to a simple, versatile approach for extending the lifetime of batteries.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Shuo Jin, Yue Deng, Pengyu Chen, Shifeng Hong, Regina Garcia‐Mendez, Arpita Sharma, Nyalaliska W. Utomo, Yiqi Shao, Rong Yang, Lynden A. Archer
onlinelibrary.wiley.com/doi/10.1002/anie.202300823

Cationic Tetrylene‐Iron(0) Complexes: Access Points for Cooperative, Reversible Bond Activation and Open‐Shell Iron(−I) Ferrato‐Tetrylenes

Par admin / 23 mars 2023 23 mars 2023 / Non classé

Cationic tetrylene centres, built into a chelating ligand framework, allow for the formation of reactive CO-free iron(0) complexes. For Sn, a highly reactive high-spin, open-shell d⁸ complex is formed, capable of the cooperative, reversible activation of H₂ at the Sn−Fe interface. Both E^II−Fe⁰ complexes (E=Ge, Sn) also undergo one-electron reduction to form unique iron(−I) ferrato-tetrylenes, a compound class which was previously unknown.

Abstract

The open-shell cationic stannylene-iron(0) complex 4 (4=[^PhiPDippSn⋅Fe⋅IPr]⁺; ^PhiPDipp={[Ph₂PCH₂Si(ⁱPr)₂](Dipp)N}; Dipp=2,6-ⁱPr₂C₆H₃; IPr=[(Dipp)NC(H)]₂C:) cooperatively and reversibly cleaves dihydrogen at the Sn−Fe interface under mild conditions (1.5 bar, 298 K), in forming bridging hydrido-complex 6. The One-electron oreduction of the related Ge^II−Fe⁰ complex 3 leads to oxidative addition of one C−P linkage of the ^PhiPDipp ligand in an intermediary Fe^−I complex, leading to Fe^I phosphide species 7. One-electron reduction reaction of 4 gives access to the iron(−I) ferrato-stannylene, 8, giving evidence for the transient formation of such a species in the reduction of 3. The covalently bound tin(II)-iron(−I) compound 8 has been characterised through EPR spectroscopy, SQUID magnetometry, and supporting computational analysis, which strongly indicate a high localization of electron spin density at Fe^−I in this unique d⁹-iron complex.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Philip M. Keil, Ademola Soyemi, Kilian Weisser, Tibor Szilvási, Christian Limberg, Terrance J. Hadlington
onlinelibrary.wiley.com/doi/10.1002/anie.202218141

Synthesis of a π‐Extended Double [9]Helicene

Par admin / 23 mars 2023 23 mars 2023 / Non classé

An unprecedented π-extended double [9]helicene D9H with D₂ symmetry has been synthesized and characterized by single-crystal X-ray diffraction. D9H exhibits a high photoluminescence quantum yield (Φ=18 %) in the near-infrared region and notable dissymmetry factor (g_CD=0.019) in the visible region.

Abstract

Double helicenes are appealing chiral frameworks. Their π-extension is desirable to achieve (chir)optical response in the visible and near-infrared (NIR) region, but access to higher double [n]helicenes (n≥8) has remained challenging. Herein, we report an unprecedented π-extended double [9]helicene (D9H), unambiguously revealing its structure by single-crystal X-ray diffraction. D9H shows remarkable NIR emission from 750 to 1100 nm with a high photoluminescence quantum yield of 18 %. In addition, optically pure D9H exhibits panchromatic circular dichroism with a notable dissymmetry factor (g_CD) of 0.019 at 590 nm, which is among the highest in the visible region for reported helicenes.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jingyun Tan, Xiushang Xu, Jun Liu, Serhii Vasylevskyi, Zesen Lin, Ryota Kabe, Yingping Zou, Klaus Müllen, Akimitsu Narita, Yunbin Hu
onlinelibrary.wiley.com/doi/10.1002/anie.202218494

A Multiresponsive Functional AIEgen for Spatiotemporal Pattern Control and All‐round Information Encryption

Par admin / 23 mars 2023 23 mars 2023 / Non classé

A chromone-based aggregation-induced emission (AIE) fluorogen called CPVCM which can undergo a specific amination with primary amines and photoarrangement under UV irradiation at the same active site were reported, along with its applications of developing multiple-colored images, a quick response code with dynamic colors and an all-round information encryption system which indicated the properties of multiple controls and responses.

Abstract

Functional materials with multi-responsive properties and good controllability are highly desired for developing bioinspired and intelligent multifunctional systems. Although some chromic molecules have been developed, it is still challenging to realize in situ multicolor fluorescence changes based on a single luminogen. Herein, we reported an aggregation-induced emission (AIE) luminogen called CPVCM, which can undergo a specific amination with primary amines to trigger luminescence change and photoarrangement under UV irradiation at the same active site. Detailed mechanistic insights were carried out to illustrate the reactivity and reaction pathways. Accordingly, multiple-colored images, a quick response code with dynamic colors, and an all-round information encryption system were demonstrated to show the properties of multiple controls and responses. It is believed that this work not only provides a strategy to develop multiresponsive luminogens but also develops an information encryption system based on luminescent materials.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Xinyuan He, Jianyu Zhang, Xinyue Liu, Zhuwei Jin, Jacky W. Y. Lam, Ben Zhong Tang
onlinelibrary.wiley.com/doi/10.1002/anie.202300353

Cobalt‐Catalyzed Regiodivergent and Enantioselective Intermolecular Coupling of 1,1‐Disubstituted Allenes and Aldehydes

Par admin / 23 mars 2023 23 mars 2023 / Non classé

A series of new protocols for regiodivergent and enantioselective coupling of 1,1-disubstituted allenes and aldehydes promoted by easily accessible Co complexes were developed. These processes represent the first example of transformations through enantioselective oxidative cyclization of allenes and aldehydes with diverse regioselectivities accurately controlled by chiral ligands.

Abstract

Catalytic enantioselective coupling of 1,1-disubstituted allenes and aldehydes through regiodivergent oxidative cyclization followed by stereoselective protonation or reductive elimination promoted by chiral phosphine-Co complexes is presented. Such processes represent unprecedented and unique reaction pathways for Co catalysis that enable catalytic enantioselective generation of metallacycles with divergent regioselectivity accurately controlled by chiral ligands, affording a wide range of allylic alcohols and homoallylic alcohols that are otherwise difficult to access without the need of pre-formation of stoichiometric amounts of alkenyl- and allyl-metal reagents in up to 92 % yield, >98 : 2 regioselectivity, >98 : 2 dr and >99.5 : 0.5 er.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Wei Huang, Jiahui Bai, Yinlong Guo, Qinglei Chong, Fanke Meng
onlinelibrary.wiley.com/doi/10.1002/anie.202219257

Exciton Localization for Highly Luminescent Two‐Dimensional Tin‐Based Hybrid Perovskites through Tin Vacancy Tuning

Par admin / 23 mars 2023 23 mars 2023 / Non classé

A universal and efficient Sn²⁺ vacancy tuning strategy is proposed to achieve strongly localized excitons in two-dimensional (OA)₂SnI₄ (OA=octylammonium) perovskite nanosheets by separating corner-sharing [SnI₆]⁴⁻ octahedra, thereby promoting their photoluminescence quantum yield (PLQY) to ≈64 %, which is among the highest values reported thus far for tin iodide perovskites.

Abstract

Exciton localization is an approach for preparing highly luminescent semiconductors. However, realizing strongly localized excitonic recombination in low-dimensional materials such as two-dimensional (2D) perovskites remains challenging. Herein, we first propose a simple and efficient Sn²⁺ vacancy (V_Sn) tuning strategy to enhance excitonic localization in 2D (OA)₂SnI₄ (OA=octylammonium) perovskite nanosheets (PNSs), increasing their photoluminescence quantum yield (PLQY) to ≈64 %, which is among the highest values reported for tin iodide perovskites. Combining experimental with first-principles calculation results, we confirm that the significantly increased PLQY of (OA)₂SnI₄ PNSs is primarily due to self-trapped excitons with highly localized energy states induced by V_Sn. Moreover, this universal strategy can be applied for improving other 2D Sn-based perovskites, thereby paving a new way to fabricate diverse 2D lead-free perovskites with desirable PL properties.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yameng Chen, Zhaoyu Wang, Youchao Wei, Yongsheng Liu, Maochun Hong
onlinelibrary.wiley.com/doi/10.1002/anie.202301684

Tailoring the Asymmetric Structure of NH2‐UiO‐66 Metal‐Organic Frameworks for Light‐promoted Selective and Efficient Gold Extraction and Separation

Par admin / 23 mars 2023 23 mars 2023 / Non classé

By precisely controlling the MOF structure, the electronic structure of the amino group was optimized to act as a double donor of electrons and protons in the process of gold reduction and desorption, thus realizing the selective adsorption, rapid reduction and efficient recovery of gold ions in electronic waste.

Abstract

Designing adsorption materials with high adsorption capacities and selectivities is highly desirable for precious metal recovery. Desorption performance is also particularly crucial for subsequent precious metal recovery and adsorbent regeneration. Herein, a metal–organic framework (MOF) material (NH₂-UiO-66) with an asymmetric electronic structure of the central zirconium oxygen cluster has an exceptional gold extraction capacity of 2.04 g g⁻¹ under light irradiation. The selectivity of NH₂-UiO-66 for gold ions is up to 98.8 % in the presence of interfering ions. Interestingly, the gold ions adsorbed on the surface of NH₂-UiO-66 spontaneously reduce in situ, undergo nucleation and growth and finally achieve the phase separation of high-purity gold particles from NH₂-UiO-66. The desorption and separation efficiency of gold particles from the adsorbent surface reaches 89 %. Theoretical calculations indicate that -NH₂ functions as a dual donor of electrons and protons, and the asymmetric structure of NH₂-UiO-66 leads to energetically advantageous multinuclear gold capture and desorption. This adsorption material can greatly facilitate the recovery of gold from wastewater and can easily realize the recycling of the adsorbent.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jiazhen Cao, Zhenmin Xu, Yao Chen, Shuangjun Li, Yue Jiang, Lele Bai, Han Yu, Hexing Li, Zhenfeng Bian
onlinelibrary.wiley.com/doi/10.1002/anie.202302202