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Vladimir Vasil′evich Markovnikov (1837–1904) was a Russian chemist whose graduate research at Kazan Imperial University from 1860–1869 gave us, among other things, one of the most enduring empirical rules in organic chemistry. Markovnikov's Rule for electrophilic addition was first published in the inaugural volume of the Journal of the Russian Chemical Society (Zh. Russ. Khim. O‐va.), but it was not until a year later when it was published in German that it received attention internationally. The rule itself was worded differently from the most common modern versions, in that it is expressed in terms of the electronegative part of the adding reagent. It has been suggested that this rule was the result of an inspired guess, but a careful examination of Markovnikov's graduate dissertations reveals a very different picture. In the dissertations, there is a careful build‐up of logic from which the rule itself, as defined by Markovnikov, emerges naturally. Markovnikov's Rule was most decidedly not an inspired guess. [ABSTRACT FROM AUTHOR]

The Markovnikov rule, known to every student of organic chemistry, was formulated 150 years ago, in 1869. During its long history (almost as long as the history of organic chemistry itself), attitudes towards this famous statement of chemical reactivity have evolved from indifference up to the 1930s, through common acceptance as a useful educational paradigm with marginal use in research up to the 1990s, to its vigorous relaunch as an important designation of regioselectivity in the last few decades. The unexpected new popularity of the classical rule is accounted for by the rapid expansion in catalytic addition reactions and their critical importance as highly effective atom‐economical, regioselective methods in modern organic synthesis. A historical outline of the life and achievements of Vladimir Markovnikov is included to reveal the very wide scope of his interests as well as his prophetic predictions on structure, reactivity, selectivity, stereochemistry, and other key issues of organic chemistry. As a general rule: During its 150 year long history the Markovnikov rule, formulated by Vladimir Markovnikov, has undergone a rather incredible evolution. After starting as an empirical rule describing a particular organic reaction, it has become an important designation of regioselectivity that is applicable to a huge range of important organic transformations. [ABSTRACT FROM AUTHOR]

Qi and Deyang exerted considerable effort to prepare and characterize the MOF-supported copper catalysts, which initially posed the greatest challenge for our group. It was lucky that the pillar-layered MOF reported in this I Angewandte i paper was among the first materials I designed for catalyst immobilization. I "I am waiting for the day when someone will discover recyclable heterogeneous catalysts with millions of turnovers for organic synthesis ... My group has fun by hiking, fishing, and singing at karaoke bars." i Find out more about Jian He in his Introducing ... Profile. [Extracted from the article]

I "The next big goal of my research is to explore more efficient strategies for the ring-opening polymerization of macrocyclic monomers ... I am waiting for the day when someone will discover a new code table beyond the periodic table, bringing us to think about the chemical world in a different way." i Find out more about Hanchu Huang in his Introducing ... Profile. The idea of the "click polymerization trigger" behind our paper came about while exploring the anionic ring-opening polymerization of macrocyclic allylic sulfides. B The most important factor in the choice of my current research topic was b recognizing that achieving ring-opening polymerization of various macrocyclic monomers would be exciting. [Extracted from the article]

“I like refereeing because it keeps me updated and it forces me to read recent interesting work in a critical manner. What I look at first in a publication are the abstract and the conclusion...” This and more about Jan‐E. Bäckvall can be found on page 15796. [ABSTRACT FROM AUTHOR]

Selective structural modification of amino acids and peptides is a central strategy in organic chemistry, chemical biology but also in pharmacology and material science. In this context, the formation of tetrazole rings, known to possess significant therapeutic properties, would expand the chemical space of unnatural amino acids but has received less attention. In this study, we demonstrated that the classic unimolecular Wolff rearrangement of α‐amino acid‐derived diazoketones could be replaced by a faster intermolecular cycloaddition reaction with aryldiazonium salts under identical practical conditions. This strategy provides an efficient synthetic platform that could transform proteinogenic α‐amino acids into a plethora of unprecedented tetrazole‐decorated amino acid derivatives with preservation of the stereocenters. Density functional theory studies shed some light on the reaction mechanism and provided information regarding the origins of the chemo‐ and regioselectivity. Furthermore, this diazo‐cycloaddition protocol was applied to construct tetrazole‐modified peptidomimetics and drug‐like amino acid derivatives. [ABSTRACT FROM AUTHOR]

The use of molecular oxygen as the terminal oxidant in transition metal catalyzed oxidative process is an appealing and challenging task in organic synthetic chemistry. Here, we report a Ni‐catalyzed hydroxylarylation of unactivated alkenes enabled by a β‐diketone ligand with high efficiency and excellent regioselectivity employing molecular oxygen as the oxidant and hydroxyl source. This reaction features mild conditions, broad substrate scope and incredible heterocycle compatibility, providing a variety of β‐hydroxylamides, γ‐hydroxylamides, β‐aminoalcohols, γ‐aminoalcohols, and 1,3‐diols in high yields. The synthetic value of this methodology was demonstrated by the efficient synthesis of two bioactive compounds, (±)‐3′‐methoxyl citreochlorol and tea catechin metabolites M4. [ABSTRACT FROM AUTHOR]

C(sp3)−H oxyfunctionalization, the insertion of an O‐atom into C(sp3)−H bonds, streamlines the synthesis of complex molecules from easily accessible precursors and represents one of the most challenging tasks in organic chemistry with regard to site and stereoselectivity. Biocatalytic C(sp3)−H oxyfunctionalization has the potential to overcome limitations inherent to small‐molecule‐mediated approaches by delivering catalyst‐controlled selectivity. Through enzyme repurposing and activity profiling of natural variants, we have developed a subfamily of α‐ketoglutarate‐dependent iron dioxygenases that catalyze the site‐ and stereodivergent oxyfunctionalization of secondary and tertiary C(sp3)−H bonds, providing concise synthetic routes towards four types of 92 α‐ and β‐hydroxy acids with high efficiency and selectivity. This method provides a biocatalytic approach for the production of valuable but synthetically challenging chiral hydroxy acid building blocks. [ABSTRACT FROM AUTHOR]

Direct synthesis of gem‐difluorinated carbocyclic molecules represents a longstanding challenge in organic chemistry. Herein, a Rh‐catalyzed [3+2] cycloaddition reaction between readily available gem‐difluorinated cyclopropanes (gem‐DFCPs) and internal olefins has been developed, enabling the efficient synthesis of gem‐difluorinated cyclopentanes with good functional group compatibility, excellent regioselectivity and good diastereoselectivity. The resulting gem‐difluorinated products can undergo downstream transformations to access various mono‐fluorinated cyclopentenes and cyclopentanes. This reaction demonstrates the use of gem‐DFCPs as a type of "CF2" C3 synthon for cycloaddition under transition metal catalysis, which provides potential strategy for synthesizing other gem‐difluorinated carbocyclic molecules. [ABSTRACT FROM AUTHOR]

The chemistry community is currently witnessing a surge of scientific discoveries in organic chemistry supported by machine learning (ML) techniques. Whereas many of these techniques were developed for big data applications, the nature of experimental organic chemistry often confines practitioners to small datasets. Herein, we touch upon the limitations associated with small data in ML and emphasize the impact of bias and variance on constructing reliable predictive models. We aim to raise awareness to these possible pitfalls, and thus, provide an introductory guideline for good practice. Ultimately, we stress the great value associated with statistical analysis of small data, which can be further boosted by adopting a holistic data‐centric approach in chemistry. [ABSTRACT FROM AUTHOR]

Synthetic methodology is considered a holy grail in both organic chemistry and materials science. Over the past few decades, researchers have explored graphene‐type molecules (or nanographenes) through classic Scholl oxidative cyclodehydrogenation. Despite the successes achieved with various nanographenes, the development of new methods to synthesize these highly desired molecules lags behind. Herein, we developed a facile and effective method to produce a series of nanographenes bearing nitrogen (N)‐doped pentagon‐heptagon pairs in acceptable yields. Modification of the heptagonal ring endowed the resultant nanographenes with tunable physicochemical properties; for instance, M9 exhibited both aggregation‐caused quenching and aggregation‐induced emission behavior. Most strikingly, novel nanographenes containing N‐doped pentagon‐octagon pairs were also obtained using the same synthetic strategy, demonstrating the superior versatility and efficiency of the proposed ring expansion method. [ABSTRACT FROM AUTHOR]

The palladium‐catalyzed asymmetric carboamination reaction is one of the most significant transformations in organic chemistry. Herein, we report the first palladium‐catalyzed asymmetric alleneamination of β,γ‐unsaturated hydrazones with propargylic acetates. This protocol enables the efficient installation of various multisubstituted allene groups onto dihydropyrazoles in good yields with excellent enantioselectivities. The chiral sulfinamide phosphine ligand Xu‐5 exhibits highly efficient stereoselective control in this protocol. The salient features of this reaction include the readily available starting materials, a broad substrate scope, an easy scale‐up, mild reaction conditions and versatile transformations. [ABSTRACT FROM AUTHOR]

Recently, stable diazoalkenes have received significant attention as a new substance class in organic chemistry. While their previous synthetic access was exclusively limited to the activation of nitrous oxide, we here establish a much more general synthetic approach utilizing a Regitz‐type diazo transfer with azides. Importantly, this approach is also applicable to weakly polarized olefins such as 2‐pyridine olefins. The new pyridine diazoalkenes are not accessible by the activation of nitrous oxide, allowing for a considerable extension of the scope of this only recently accessed functional group. The new diazoalkene class has properties distinct from the previously reported classes, such as photochemically triggered loss of dinitrogen affording cumulenes and not C−H insertion products. Pyridine‐derived diazoalkenes represent the so far least polarized stable diazoalkene class reported. [ABSTRACT FROM AUTHOR]

Amide is one of the most widespread functional groups in organic and bioorganic chemistry, and it would be valuable to achieve stereoselective C(sp3)−H functionalization in amide molecules. Palladium(II) catalysis has been prevalently used in the C−H activation chemistry in the past decades, however, due to the weakly‐coordinating feature of simple amides, it is challenging to achieve their direct C(sp3)−H functionalization with enantiocontrol by PdII catalysis. Our group has developed sulfoxide‐2‐hydroxypridine (SOHP) ligands, which exhibited remarkable activity in Pd‐catalyzed C(sp2)−H activation. In this work, we demonstrate that chiral SOHP ligands served as an ideal solution to enantioselective C(sp3)−H activation in simple amides. Herein, we report an efficient asymmetric PdII/SOHP‐catalyzed β‐C(sp3)−H arylation of aliphatic tertiary amides, in which the SOHP ligand plays a key role in the stereoselective C−H deprotonation‐metalation step. [ABSTRACT FROM AUTHOR]

Commercially available stock solutions of organolithium reagents are well‐implemented tools in organic and organometallic chemistry. However, such solutions are inherently contaminated with lithium halide salts, which can complicate certain synthesis protocols and purification processes. Here, we report the isolation of chloride‐free methyllithium employing K[N(SiMe3)2] as a halide‐trapping reagent. The influence of distinct LiCl contaminations on the 7Li‐NMR chemical shift is examined and their quantification demonstrated. The structural parameters of new chloride‐free monomeric methyllithium complex [(Me3TACN)LiCH3], ligated by an azacrown ether, are assessed by comparison with a halide‐contaminated variant and monomeric lithium chloride [(Me3TACN)LiCl], further emphasizing the effect of halide impurities. [ABSTRACT FROM AUTHOR]

Axially chiral molecules bearing multiple stereogenic axes are of great importance in the field of organic chemistry. However, the efficient construction of atropisomers featuring two different types of stereogenic axes has rarely been explored. Herein, we report the novel atroposelective synthesis of configurationally stable axially chiral B,N‐heterocycles. By using stepwise asymmetric allylic substitution‐isomerization (AASI) strategy, diaxially chiral B,N‐heterocycles bearing B−C and C−N axes that are related to the moieties of axially chiral enamines and arylborons were also obtained. In this case, all four stereoisomers of diaxially chiral B,N‐heterocycles were stereodivergently afforded in high enantioselectivities. Density functional theory (DFT) studies demonstrated that the NH⋅⋅⋅π interactions played a unique role in the promotion of stereospecific isomerization, thereby leading to the highly efficient central‐to‐axial chirality transfer. [ABSTRACT FROM AUTHOR]

Aromatic carboxylic anhydrides are ubiquitous building blocks in organic materials chemistry and have received considerable attention in the synthesis of organic semiconductors, pigments, and battery electrode materials. Here we extend the family of aromatic carboxylic anhydrides with a unique new member, a conjugated cyclophane with four anhydride groups. The cyclophane is obtained in a three‐step synthesis and can be functionalised efficiently, as shown by the conversion into tetraimides and an octacarboxylate. Crystal structures reveal the high degree of porosity achievable with the new building block. Excellent electrochemical properties and reversible reduction to the tetraanions are shown for the imides; NMR and EPR measurements confirm the global aromaticity of the dianions and evidence the global Baird aromaticity of the tetraanions. Considering the short synthesis and unique properties, we expect widespread use of the new building block in the development of organic materials. [ABSTRACT FROM AUTHOR]

Direct asymmetric functionalization of the inert α C−H bonds of N‐unprotected propargylic amines is a big challenge in organic chemistry, due to the low acidity (pKa≈42.6) of the α C−H bonds and interruption of the nucleophilic NH2 group. By using a chiral pyridoxal as carbonyl catalyst, we have successfully realized direct asymmetric α‐C−H addition of N‐unprotected propargylic amines to trifluoromethyl ketones, producing a broad range of chiral alkynyl β‐aminoalcohols in 54–84 % yields with excellent stereoselectivities (up to 20 : 1 dr and 99 % ee). The α C−H bonds of propargylic amines are greatly activated by the pyridoxal catalyst via the formation of an imine intermediate, resulting in the increase of acidity by up to 1022 times (from pKa 42.6 to pKa 20.1), which become acidic enough to be deprotonated under mild conditions for the asymmetric addition. This work presented an impressive example for asymmetric functionalization of inert C−H bonds enabled by an organocatalyst. [ABSTRACT FROM AUTHOR]

Triangulenes have attracted enormous interest in organic chemistry and materials science, but suffer from their high instability towards oxygen. Embedding heteroatoms into triangulenes provides a new class of ambient stable materials for various applications. However, [3]heterotriangulenes have dominated the chemistry of heteroatom‐doped triangulenes, while their higher homologues have been rarely explored. In this work, we synthesize a new [4]heterotriangulene with three oxygen‐boron‐oxygen (OBO) segments incorporated into the zigzag edges. The planar geometry of the OBO‐doped [4]triangulene is demonstrated by single‐crystal X‐ray diffraction. Self‐assembly on metal surfaces reveals substrate‐dependent nanostructures, leading to different long‐range ordered 2D patterns on Ag and Cu substrates with negligible defects. [ABSTRACT FROM AUTHOR]

A simplified and appealing strategy via a chiral catalyst to facilitate the electrochemical process and provide asymmetric induction of radical reactions is particularly desirable and would have potential applications in electrosynthesis, organic chemistry, and drug discovery. Here, we introduced a novel electrolytic system that diverts the standard ionic reactivity to new catalytic functions, enabling mechanistically distinct single‐electron transfer‐based enantioselective routes to exhibit a brand‐new pattern of reactivity—electricity‐driven asymmetric catalysis as a privileged chiral platform for enantioselective radical allylation. The nickel‐catalyzed activation of nucleophiles triggered a single‐electron transfer process to provide a chiral catalyst‐bound radical cation intermediate, which could be applied as an alternative strategy for the development of stereocontrolled radical reactions. [ABSTRACT FROM AUTHOR]

Boron‐embedded heteroacenes (boraacenes) have attracted enormous interest in organic chemistry and materials science. However, extending the skeleton of boraacenes to higher acenes (N≥6) is synthetically challenging because of their limited stability under ambient conditions. Herein, we report the synthesis of boron‐embedded heptacene (DBH) and nonacene (DBN) as the hitherto longest boraacenes. The former is highly stable (even after 240 h in tetrahydrofuran), while the latter is air‐sensitive with the half‐life (t1/2) of 11.8 min. The structures of both compounds are verified by single‐crystal X‐ray diffraction, revealing a linear backbone with an antiaromatic C4B2 core. Photophysical characterizations associated with theoretical calculations indicate that both compounds exhibit highly efficient anti‐Kasha emissions. Remarkably, the air‐stable DBH manifests an ultrahigh photoluminescence quantum yield (PLQY) of 98±2 % and can be chemically reduced to its radical anion and dianion states, implying the value of boron‐doped higher acenes as novel functional materials. [ABSTRACT FROM AUTHOR]

In honor of the 90th birthday of Professor Carl Djerassi, J. I. Seeman has assembled a collection of poignant quotes and excerpts from Djerassi's writings which embody his remarkable life experiences, his philosophies of life, and his unique personality. [ABSTRACT FROM AUTHOR]

The article profiles author Varinder K. Aggarwal. Topics include his educational background, awards received, and his research interest in organic chemistry. Also mentioned are his favorite fiction author V. S. Naipaul, the best and worst advice he received, and contraceptive pill as most significant scientific advance of the last 100 years.

In terms of molecules and specific reaction examples, organic chemistry features an impressive, exponential growth. However, new reaction classes/types that fuel this growth are being discovered at a much slower and only linear (or even sublinear) rate. The proportion of newly discovered reaction types to all reactions being performed keeps decreasing, suggesting that synthetic chemistry becomes more reliant on reusing the well‐known methods. The newly discovered chemistries are more complex than decades ago and allow for the rapid construction of complex scaffolds in fewer numbers of steps. We study these and other trends in the function of time, reaction‐type popularity and complexity based on the algorithm that extracts generalized reaction class templates. These analyses are useful in the context of computer‐assisted synthesis, machine learning (to estimate the numbers of models with sufficient reaction statistics), and identifying erroneous entries in reaction databases. [ABSTRACT FROM AUTHOR]

The Diels–Alder reaction is one of the most popular reactions in organic chemistry. However, its use in the field of on‐surface synthesis is hampered by the spatial restrictions of this cycloaddition reaction. Herein we selected a cyclic strained triyne to demonstrate an on‐surface hexadehydro‐Diels–Alder reaction in a single molecule. The reaction was studied in detail by means of atomic force microscopy (AFM) with CO‐functionalized tips. Our results pave the way to use this iconic pericyclic reaction for on‐surface synthesis, introducing the concept of atom economy in the field. [ABSTRACT FROM AUTHOR]

The pursuit of efficient synthetic route to thienoacenes represents an appealing yet challenging task in the fields of both organic synthetic chemistry and organic functional materials. In this work, we disclose a rhodium‐catalyzed cascade C−H annulation of phenacyl phosphoniums with (benzo)thiophenes via a Heck‐type pathway to provide a new class of planar thienoacenes, which involves the formation of three Caryl‐Caryl bonds and one Caryl−O bond in a single operation. The neutral S,O‐heteroacenes exhibit superior stability and adopt a herringbone‐like packing mode with efficient π–π stacking in the crystals, suggesting their potential in organic semiconducting materials. This work first exemplifies the superiority of cascade oxidative C−H annulation involving a Heck‐type pathway in the development of concise access to heteroacenes. [ABSTRACT FROM AUTHOR]

Keywords: Diederich, François; Fullerene; Medicinal Chemistry; Obituary; Supramolecular Chemistry EN Diederich, François Fullerene Medicinal Chemistry Obituary Supramolecular Chemistry 11562 11567 6 05/13/21 20210517 NES 210517 François Diederich, Professor of Organic Chemistry and long-time Chair of the Editorial Board of I Angewandte Chemie i , sadly passed away on September 23, 2020. Diederich, François, Fullerene, Medicinal Chemistry, Obituary, Supramolecular Chemistry 32 "Spacer-controlled multiple functionalization of fullerenes": C. Thilgen, S. Sergeyev, F. Diederich in Topics in Current Chemistry (Eds.: C. A. Schalley, F. Vögtle, K. H. Dötz), Springer-Verlag, Berlin, 2004, pp. 1 - 61. 33 F. Diederich, Y. Rubin, Angew. He will be remembered for his groundbreaking research in the chemistry of fullerenes and carbon-rich molecules, in supramolecular and medicinal chemistry, as an engaging teacher, and as a generous and fascinating human being. [Extracted from the article]

Examples from different research areas of Siegfried Hünig are displayed to remind us that organic chemistry owes much more than Hünig's base to this exceptionally versatile and creative chemist. The main research lines dealing with the synthesis and physical characterization of new dyes, multistage redox systems, and organic metals will be presented as well as his contributions to enamine chemistry, the discovery of diimine as a hydrogenation agent, and nucleophilic acylation with trimethylsilyl cyanide, which are less well‐known nowadays. In addition, exotic compounds with parallel C=C and N=N bonds were systematically studied in Hünig's group. Reflecting on the development of his research demonstrates both the importance of a systematic approach and how fruitful entirely unexpected results are if they meet a "well‐prepared mind". During Hünig's academic career, teaching played an indisputable role. His efforts in modernizing the chemistry institute at Würzburg and his support of young researchers in the academic system in Germany are also highlighted. [ABSTRACT FROM AUTHOR]

“What I look for first in a publication is the abstract and schemes. The most important thing I learned from my parents is to work hard. …︁” This and more about Janine Cossy can be found on page 7634–7635. [ABSTRACT FROM AUTHOR]

The synthesis of robust high‐spin carbon radicals is an important topic in organic chemistry. Toward this end, several porphyrin‐stabilized radicals have been systematically explored. A singly naphthalene‐fused porphyrin radical was synthesized by a reaction sequence consisting of a Suzuki–Miyaura coupling of β‐borylated porphyrin with 2‐bromobenzaldehyde, addition of mesityl Grignard reagent, intramolecular Friedel–Crafts alkylation, and final oxidation with DDQ or tBuOK/O2. This strategy was also used to synthesize doubly naphthalene‐fused porphyrins and syn‐ and anti‐fused‐anthracene‐bridged porphyrin dimers. While singly naphthalene‐fused porphyrin radical has been shown to be a stable monoradical, doubly naphthalene‐fused porphyrins and anti‐fused‐anthracene‐bridged porphyrin dimers have been shown to be closed‐shell molecules. Finally, the syn‐dimer was characterized as a surprisingly stable radical (t1/2=28 days under ambient air and at 80 °C) that is storable for more than several months, despite its high‐spin triplet ground‐state carbon diradical. [ABSTRACT FROM AUTHOR]

Synthesis of a carbon nanobelt (CNB) is a very challenging task in organic chemistry. Herein, we report the successful synthesis of an octabenzo[12]cyclacene based CNB (6), which can be regarded as a sidewall fragment of a (12,0) carbon nanotube. The key intermediate compound, a tetraepoxy nanobelt (5), was first synthesized by Diels–Alder reaction, and subsequent reductive aromatization gave the fully conjugated CNB 6. X‐ray crystallographic analysis unambiguously confirmed the belt‐shaped structure of 6. 1H NMR spectrum and theoretical calculations (ACID, NICS, and 2D/3D ICSS) revealed localized aromaticity and stronger shielding chemical environment in the inner region of the belt. The optical properties (absorption and emission) of 6 were studied and correlated to its electronic structure. Strain analysis indicates that the phenyl substituents at the zigzag edges are crucial to the successful synthesis of 6. This report presents a new strategy towards highly strained CNBs. [ABSTRACT FROM AUTHOR]

Directed evolution of stereo‐, regio‐, and chemoselective enzymes constitutes a unique way to generate biocatalysts for synthetically interesting transformations in organic chemistry and biotechnology. In order for this protein engineering technique to be efficient, fast, and reliable, and also of relevance to synthetic organic chemistry, methodology development was and still is necessary. Following a description of early key contributions, this review focuses on recent developments. It includes optimization of molecular biological methods for gene mutagenesis and the design of efficient strategies for their application, resulting in notable reduction of the screening effort (bottleneck of directed evolution). When aiming for laboratory evolution of selectivity and activity, second‐generation versions of Combinatorial Active‐Site Saturation Test (CAST) and Iterative Saturation Mutagenesis (ISM), both involving saturation mutagenesis (SM) at sites lining the binding pocket, have emerged as preferred approaches, aided by in silico methods such as machine learning. The recently proposed Focused Rational Iterative Site‐specific Mutagenesis (FRISM) constitutes a fusion of rational design and directed evolution. On‐chip solid‐phase chemical gene synthesis for rapid library construction enhances library quality notably by eliminating undesired amino acid bias, the future of directed evolution? [ABSTRACT FROM AUTHOR]

Zeise's salt, KPt(C2H4)Cl3, was the first characterized organometallic compound; it was also the first olefin π‐complex. It was published in 1825–1830 in the middle of a fight between Dumas on the one hand and Berzelius and Liebig on the other, who defended the etherin (ethylene) and radical theories, respectively. Although Zeise's formulation as a compound containing ethylene was vindicated, the fight went on for many years. This was a time when the theories of organic chemistry were being developed, before any clear understanding of the nature of molecules, bonding, and structure. Zeise thought of the structure of his salt as a product of the addition of PtCl2 to ethylene. Jensen assumed a central bonding to ethylene but needed theoretical assistance to explain it. His attempt to obtain such an explanation from Hückel failed, and it was Dewar who explained the nature of π‐complexes in molecular orbital terms in 1951. [ABSTRACT FROM AUTHOR]

Sonogashira‐type cross‐couplings are one of the most significant alkynylations in organic chemistry. One of the first palladium‐catalyzed intramolecular Heck/Sonogashira reactions of alkenes with terminal alkynes is now reported. With this method, a variety of uniquely substituted chiral benzene‐fused heterocycles bearing a propargyl‐substituted all‐carbon quaternary stereocenter were obtained in a straightforward, high‐yielding, and highly stereoselective manner under mild conditions. Salient features of this process include the use of readily available substrates, high selectivities, a broad substrate scope as well as versatile product functionalizations. [ABSTRACT FROM AUTHOR]

The tunable chemistry linked to the organic/inorganic components in colloidal nanocrystals (NCs) and metal–organic frameworks (MOFs) offers a rich playground to advance the fundamental understanding of materials design for various applications. Herein, we combine these two classes of materials by synthesizing NC/MOF hybrids comprising Ag NCs that are in intimate contact with Al‐PMOF ([Al2(OH)2(TCPP)]) (tetrakis(4‐carboxyphenyl)porphyrin (TCPP)), to form Ag@Al‐PMOF. In our hybrids, the NCs are embedded in the MOF while still preserving electrical contact with a conductive substrate. This key feature allows the investigation of the Ag@Al‐PMOFs as electrocatalysts for the CO2 reduction reaction (CO2RR). We show that the pristine interface between the NCs and the MOFs accounts for electronic changes in the Ag, which suppress the hydrogen evolution reaction (HER) and promote the CO2RR. We also demonstrate a minor contribution of mass‐transfer effects imposed by the porous MOF layer under the chosen testing conditions. Furthermore, we find an increased morphological stability of the Ag NCs when combined with the Al‐PMOF. The synthesis method is general and applicable to other metal NCs, thus revealing a new way to think about rationally tailored electrocatalytic materials to steer selectivity and improve stability. [ABSTRACT FROM AUTHOR]

The direct amination of aliphatic C−H bonds has remained one of the most tantalizing transformations in organic chemistry. Herein, we report on a unique catalyst system, which enables the elusive intermolecular C(sp3)−H amination. This practical synthetic strategy provides access to aminated building blocks and fosters innovative multiple C−H amination within a new approach to aminated heterocycles. The synthetic utility is demonstrated by the synthesis of four relevant pharmaceuticals. [ABSTRACT FROM AUTHOR]

Lewis‐acid catalysis and electrochemistry represent two powerful fields that have found widespread application in organic chemistry. Reported herein is an asymmetric electrosynthesis in combination with a chiral Ni catalyst leading to an intermolecular alkylation reaction in good yields with excellent enantioselectivities (up to 97 % ee). Mechanistic studies suggest that the Lewis‐acid‐bound radical intermediate from a single‐electron anodic oxidation selectively reacts with the benzylic radical species to generate the desired adducts. [ABSTRACT FROM AUTHOR]

Abstract: There is an ongoing probing of the role of chemicals in the indoor environment. The majority of potential target substances are so‐called very volatile, volatile, and semi‐volatile organic compounds (VVOCs, VOCs, and SVOCs). Depending on their physical properties and the mass transfer conditions, they are distributed in or between the gas phase, particle phase, settled house dust, surface films, clothing, and other fabrics as well as the exposed skin and hair of the occupants themselves. Therefore, inhalation, ingestion, and dermal uptake all must be considered as relevant pathways for exposure assessment in human habitats. Exposure to VVOCs, VOCs, and SVOCs can be estimated by measuring their concentrations in relevant indoor compartments or by determining the amounts of the target compounds and/or their metabolites in urine and blood. Assessing the various routes of exposure often requires a combination of sophisticated and interdisciplinary theoretical background and experimental techniques. Consequently, close communication and collaboration between chemical and exposure scientists are needed to achieve a better understanding of human exposure to chemical substances in various indoor environments. Embedded in the toxicological context, this is the basis for assessing the corresponding health risks and for determining control strategies or approaches to limit such risks. [ABSTRACT FROM AUTHOR]

Abstract: The imino‐Nazarov cyclization of the polysubstituted pentan‐1,4‐diene‐3‐imines was realized. To this aim, a one‐pot procedure involving reductive alkenyliminylation of α,β‐unsaturated secondary amides with potassium organotrifluoroborates, followed by acid‐catalyzed imino‐Nazarov cyclization of the polysubstituted pentan‐1,4‐diene‐3‐imine intermediates, was studied systematically. This mild, operationally simple, flexible, and high‐yielding protocol efficiently affords polysubstituted pentan‐1,4‐diene‐3‐imines, cyclopentenimines, and α‐amino cyclopentenones, which are useful scaffolds in organic synthesis. The substituent effect at the C2 position of the polysubstituted pentan‐1,4‐diene‐3‐imines was studied by means of density‐functional theory calculations. Results suggested that the electron‐donating group facilitates the imino‐Nazarov cyclization process. [ABSTRACT FROM AUTHOR]

Abstract: NMR spectroscopy is an indispensable method of analysis in chemistry, which until recently suffered from high demands for space, high costs for acquisition and maintenance, and operational complexity. This has changed with the introduction of compact NMR spectrometers suitable for small‐molecule analysis on the chemical workbench. These spectrometers contain permanent magnets giving rise to proton NMR frequencies between 40 and 80 MHz. The enabling technology is to make small permanent magnets with homogeneous fields. Tabletop instruments with inhomogeneous fields have been in use for over 40 years for characterizing food and hydrogen‐containing materials by relaxation and diffusion measurements. Related NMR instruments measure these parameters in the stray field outside the magnet. They are used to inspect the borehole walls of oil wells and to test objects nondestructively. The state‐of‐the‐art of NMR spectroscopy, imaging and relaxometry with compact instruments is reviewed. [ABSTRACT FROM AUTHOR]

Abstract: Furans are versatile synthons in organic chemistry. Described is a general method for transforming furans into alkynes by dual C−C double‐bond cleavage. The reaction is proposed to proceed by sequential [4+2] cycloaddition between furan and singlet oxygen and a formal retro‐(3+2) fragmentation of the endoperoxide intermediate. A wide array of furans, including those derived from sapogenins, are amenable to this reaction, thus providing the corresponding alkynoic acids in up to 88 % yields. The synthetic utility was demonstrated by a seven‐step synthesis of the proposed structure of a pregnane natural product, aglatomin B, from a known intermediate. [ABSTRACT FROM AUTHOR]

π-Conjugated molecular cages are very challenging targets in structural organic chemistry, supramolecular chemistry, and materials science. The synthesis and physical characterizations are reported of the first three-dimensionally π-conjugated diradical molecular cage PTM-C, in which two polychlorotriphenylmethyl (PTM) radicals are linked by three bis(3,6-carbazolyl) bridges. This cage compound was synthesized mainly by intermolecular Yamamoto coupling followed by deprotonation and oxidation. It is stable and its structure was confirmed by X-ray crystallographic analysis. The two carbon-centered PTM radicals are weakly coupled through electronic interactions with the carbazole spacers, as revealed by optical, electronic, and magnetic measurements as well as theoretical calculations. [ABSTRACT FROM AUTHOR]