Sebastian Beil

We go together: Evidence is presented that the formation pathway of C₆₀ during arc‐discharge synthesis is fragment assembly, while the production of C_2m (m=35, 38, 39) is enhanced by building‐block splicing. Several features of the building blocks are proposed to predict their influence on the formation of larger C_2n fullerenes (n≥42). This provides insight into the formation of fullerenes, which is crucial to improve the yield of larger fullerenes.

Abstract

Tremendous advances in nanoscience have been made since the discovery of fullerenes. However, the short timescale of the growth process and high‐energy conditions of synthesis result in severe constraints to investigation of the mechanism of fullerene formation. In this work, we attempted to reveal the formation process by analyzing the variation in the yield of fullerenes under different conditions. Experiments and theoretical analysis show that the formation of fullerenes could be affected by the addition of polycyclic aromatic compounds. It is proposed that the formation of C₆₀ during arc‐discharge synthesis is fragment assembling, while the yield of C_2m (m=35, 38, 39) is strongly enhanced by building‐block splicing. In addition, several features of the building blocks are put forward to predict the extent of their influence to the formation of larger fullerenes C_2n (n≥42). This work not only provides essential insight into the formation process of fullerenes, but more importantly also paves the way to improving the yield of larger fullerenes selectively.

Diversity: The rapid, modular, substrate‐independent and fully predictable functionalization of polysubstituted arenes bearing C−OSO₂F, C−Br, and C−Cl sites at room temperature is showcased. In this way the arene unit can be functionalized in the presence of a fluorosulfate group or the latter can serve as a triflate surrogate.

Abstract

Since 2014, the interest in aryl fluorosulfates (ArOSO₂F) as well as their implementation in powerful applications has continuously grown. In this context, the enabling capability of ArOSO₂F will strongly depend on the substitution pattern of the arene, which ultimately dictates its overall function as drug candidate, material, or bio‐linker. This report showcases the modular, substrate‐independent, and fully predictable, selective functionalization of polysubstituted arenes bearing C−OSO₂F, C−Br, and C−Cl sites, which makes it possible to diversify the arene in the presence of OSO₂F or utilize OSO₂F as a triflate surrogate. Sequential and triply selective arylations and alkylations were realized within minutes at room temperature, using a single and air‐stable Pd^I dimer.

Chemical pinching increases the distance between spin centers. This should result in reduced through‐space exchange spin coupling. In naphthalene‐bridged biscobaltocenes, the bridge plays a larger role than anticipated, with pinching leading to an increase of spin coupling. This is important for tuning interactions in spin wires for information transfer.

Abstract

Pinching molecules via chemical strain suggests intuitive consequences, such as compression at the pinched site and clothespin‐like opening of other parts of the structure. If this opening affects two spin centers, it should result in reduced communication between them. We show that for naphthalene‐bridged biscobaltocenes with competing through‐space and through‐bond pathways, the consequences of pinching are far less intuitive: despite the known dominance of through‐space interactions, the bridge plays a much larger role for exchange spin coupling than previously assumed. Based on a combination of chemical synthesis, structural, magnetic, and redox characterization, and a newly developed theoretical pathway analysis, we can suggest a comprehensive explanation for this non‐intuitive behavior. These results are of interest for molecular spintronics, as naphthalene‐linked cobaltocenes can form wires on surfaces for potential spin‐only information transfer.

Nature, Published online: 22 January 2020; doi:10.1038/s41586-019-1926-4

Redox-switchable chelation is demonstrated for a carborane cluster molecule, leading to controlled chemical or electrochemical capture and release of uranyl in monophasic or biphasic model solvent systems.

Molecular shape defines function in both biological and material settings, and chemists have developed an ever-increasing vernacular to describe these shapes. Noncanonical atropisomers—shape-defined molecules that are formally topologically trivial but are interconvertible only by complex, nonphysical multibond torsions—form a unique subset of atropisomers that differ from both canonical atropisomers (e.g., binaphthyls) and topoisomers (i.e., molecules that have identical connectivity but nonidentical molecular graphs). Small molecules, in contrast to biomacromolecules, are not expected to exhibit such ambiguous shapes. Using total synthesis, we found that the peptidic alkaloid tryptorubin A can be one of two noncanonical atropisomers. We then devised a synthetic strategy that drives the atropospecific synthesis of a noncanonical atrop-defined small molecule.

Knowledge of the hazards and associated risks from chemicals discharged to the environment has grown considerably over the past 40 years. This improving awareness stems from advances in our ability to measure chemicals at low environmental concentrations, recognition of a range of effects on organisms, and a worldwide growth in expertise. Environmental scientists and companies have learned from the experiences of the past; in theory, the next generation of chemicals will cause less acute toxicity and be less environmentally persistent and bioaccumulative. However, researchers still struggle to establish whether the nonlethal effects associated with some modern chemicals and substances will have serious consequences for wildlife. Obtaining the resources to address issues associated with chemicals in the environment remains a challenge.

Deconstructive arene cycloisomerization is reported as unprecedented strategy for the de novo synthesis of hydroxylated benzofuran, using kojic acid‐ or maltol‐derived alkynes as precursors. Several types of free hydroxyl groups are introduced into the benezofurans with different substitution patterns. A collective total synthesis of hydroxylated benzofuran‐containing natural products (11 examples) is realized.

Abstract

An unprecedented deconstructive reorganization strategy for the de novo synthesis of hydroxylated benzofurans from kojic acid‐ or maltol‐derived alkynes is reported. In this reaction, both the benzene and furan rings were simultaneously constructed, whereas the pyrone moiety of the kojic acid or maltol was deconstructed and then reorganized into the benzene ring as a six‐carbon component. Through this strategy, at least one free hydroxyl group was introduced into the benzene ring in a substitution‐pattern tunable fashion without protection–deprotection and redox adjustment. With this method, a large number of hydroxylated benzofuran derivatives with different substitution‐patterns have been prepared efficiently. This methodology has also been shown as the key step in a collective total synthesis of hydroxylated benzofuran‐containing natural products (11 examples).

Two are better than one : By combining the input from two low energy photons, thermodynamically very challenging reactions can be driven. Empirical advances combined with insights from spectroscopy have made multi‐photon excitation processes amenable to preparative‐scale photoredox chemistry. A critical look at currently developed concepts and reactions identifies challenges, pitfalls and opportunities for future research.

Abstract

The energy of visible photons and the accessible redox potentials of common photocatalysts set thermodynamic limits to photochemical reactions that can be driven by traditional visible‐light irradiation. UV excitation can be damaging and induce side reactions, hence visible or even near‐IR light is usually preferable. Thus, photochemistry currently faces two divergent challenges, namely the desire to perform ever more thermodynamically demanding reactions with increasingly lower photon energies. The pooling of two low‐energy photons can address both challenges simultaneously, and whilst multi‐photon spectroscopy is well established, synthetic photoredox chemistry has only recently started to exploit multi‐photon processes on the preparative scale. Herein, we have a critical look at currently developed reactions and mechanistic concepts, discuss pertinent experimental methods, and provide an outlook into possible future developments of this rapidly emerging area.

Nature Chemistry, Published online: 20 January 2020; doi:10.1038/s41557-019-0399-2

A conjugated diradicaloid cage has been synthesized and its aromaticity was investigated. The neutral compound and the dication have dominant monocyclic conjugation pathways and both are aromatic (the former following Hückel’s rule and the latter Baird’s rule). The tetracation ([6n + 4] π-electrons) exhibits global 3D antiaromaticity whereas the hexacation ([6n + 2] π-electrons) exhibits global 3D aromaticity and has high D3 symmetry.

Nature, Published online: 15 January 2020; doi:10.1038/s41586-020-1937-1

Synthesis of rare sugar isomers through site-selective epimerization

Nature, Published online: 14 January 2020; doi:10.1038/d41586-020-00063-y

Carla Shatz stays organized to help her spot ways in which brain circuits rewire themselves.

A simple and efficient method to generate macrocyclic structures has been developed based on the dynamic behavior of the linker bis(2,2,6,6‐tetramethylpiperidin‐1‐yl)disulfide (BiTEMPS). The prime linear structure was transformed into a (macro)cycle using the following sequence: (i) thiol‐ene reaction with a BiTEMPS derivative to afford the linear precursor, followed by (ii) an entropy‐driven transformation induced by diluting and heating. The radicals generated from BiTEMPS upon heating are highly tolerant toward a variety of chemical species, including oxygen and olefins, while they exhibit high reactivity toward exchange reactions, which can be applied to the topology transformation of various skeletons. The specific advantages of the present method, i.e., its procedural simplicity and substrate versatility, are demonstrated by the gram‐scale synthesis of cyclic compounds with low and relatively high molecular weight. The obtained products were characterized by electrospray ionization mass spectrometry (ESI‐TOF‐MS), matrix assisted laser desorption/ionization (MALDI‐TOF‐MS), and single‐crystal x‐ray diffraction analysis.