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Nature Communications, Published online: 27 June 2023; doi:10.1038/s41467-023-39079-z

The authors show that there is a positive and linear relationship between the probability of intending to pursue math and math performance, and that this relationship is stronger among boys than among girls.

Time-resolved fluorescence and ultrafast mid-infrared spectroscopies are combined to watch the decisive primary events of entry into a sustainable photoredox-catalytic cycle utilizing an affordable, non-toxic, and highly efficient titanium(IV) photocatalyst.

Abstract

Titanium-based catalysis in single electron transfer (SET) steps has evolved into a versatile approach for the synthesis of fine chemicals and first attempts have recently been made to enhance its sustainability by merging it with photo-redox (PR) catalysis. Here, we explore the photochemical principles of all-Ti-based SET-PR-catalysis, i.e. in the absence of a precious metal PR-co-catalyst. By combining time-resolved emission with ultraviolet-pump/mid-infrared-probe (UV/MIR) spectroscopy on femtosecond-to-microsecond time scales we quantify the dynamics of the critical events of entry into the catalytic cycle; namely, the singlet-triplet interconversion of the do-it-all titanocene(IV) PR-catalyst and its one-electron reduction by a sacrificial amine electron donor. The results highlight the importance of the PR-catalyst's singlet-triplet gap as a design guide for future improvements.

Electroreductive cross-electrophile coupling (eXEC) has emerged as a practical, green, sustainable, efficient electrochemical and controllable approach for constructing C−C or C−X bonds through selective cross-coupling of different electrophiles. This Mini-review summarizes the recent protocols of electroreductive cross-electrophile coupling reactions.

Abstract

Electrochemistry utilizes electrons as a potent, controllable, and traceless alternative to chemical oxidants or reductants, and typically offers a more sustainable option for achieving selective organic synthesis. Recently, the merger of electrochemistry with readily available electrophiles has been recognized as a viable and increasingly popular methodology for efficiently constructing challenging C−C and C-heteroatom bonds in a sustainable manner for complex organic molecules. In this mini-review, we have systematically summarized the most recent advances in electroreductive cross-electrophile coupling (eXEC) reactions during the last decade. Our focus has been on readily available electrophiles, including aryl and alkyl organic (pseudo)halides, as well as small molecules such as CO₂, SO₂, and D₂O.

Electrochemical analysis of the potential and reversibility of the Sm(11)/Sm(111) redox couple will inform the development of electrocatalytic Sm-driven reactions in organic synthesis.

Abstract

Samarium diiodide (SmI₂) is widely used as a strong one-electron reducing agent and is often employed to form C−C bonds in complex systems. Despite their utility, SmI₂ and related salts suffer from several drawbacks that render the use of Sm reducing agents in large-scale synthesis impractical. Here, we report factors influencing the electrochemical reduction of Sm(III) to Sm(II), towards the goal of electrocatalytic Sm(III) reduction. We probe the effect of supporting electrolyte, electrode material, and Sm precursor on Sm(II)/(III) redox and on the reducing power of the Sm species. We find that the coordination strength of the counteranion of the Sm salt affects the reversibility and redox potential of the Sm(II)/(III) couple and establish that the counteranion primarily determines the reducibility of Sm(III). Electrochemically generated SmI₂ performs similarly to commercial SmI₂ solutions in a proof-of-concept reaction. The results will provide fundamental insight to facilitate the development of Sm-electrocatalytic reactions.

A nickel-catalyzed three-component reductive protocol for hetero-difunctionalization with group 14 elements via electrochemistry is described. The cascade reaction proceeded smoothly with the diverse chlorosilanes, 1,3-enynes, primary, secondary, and tertiary alkyl bromides. Good chemo- and regioselectivities were achieved. This protocol could be extended to germanyl- and stannylalkylation of 1,3-enynes, showing its generality and versatility.

Abstract

The difunctionalization of unsaturated bonds plays a vital role in the enrichment of molecular complexity. While various catalytic methods for alkene and alkyne difunctionalization have been developed in recent years, hetero-functionalization the introduction of two different atoms has been less explored. This is mainly due to the challenges associated with achieving high chemo-, regio-, and stereoselectivity, especially when adding two similar atoms from the same group across unsaturated bonds. In this study, we describe a nickel-catalyzed, three-component reductive protocol for group 14 element hetero-difunctionalization of 1,3-enynes using electrochemistry. This new method is mild, selective, and general, allowing for the silyl-, germanyl-, and stannyl-alkylation of enynes. Various chlorosilanes as well as chlorogermans, and chlorostannanes can be successfully used in combination with aryl/alkyl-substituted 1,3-enynes and primary, secondary, and tertiary alkyl bromides in the electroreductive coupling.

Nature Communications, Published online: 12 June 2023; doi:10.1038/s41467-023-39022-2

Therapeutic antibody discovery is time and cost-intensive. Here, the authors develop a machine learning-driven method enabling accelerated design of large and diverse single-chain variable fragments with high binding efficiency, especially at high levels of diversity.

Site-selectivity in the palladium-catalyzed mono-oxidation of diols can be predicted by a model, supported by experiments and computation. It explains the selective oxidation of hydroxy groups in cis-diols and the dependency of the rate on the configuration and conformational freedom. The model predicts whether a natural product comprising multiple hydroxy groups is suited for site-selective palladium-catalyzed oxidation.

Abstract

A predictive model, shaped as a set of rules, is presented that predicts site-selectivity in the mono-oxidation of diols by palladium-neocuproine catalysis. For this, the factors that govern this site-selectivity within diols and between different diols have been studied both experimentally and with computation. It is shown that an electronegative substituent antiperiplanar to the C−H bond retards hydride abstraction, resulting in a lower reactivity. This explains the selective oxidation of axial hydroxy groups in vicinal cis-diols. Furthermore, DFT calculations and competition experiments show how the reaction rate of different diols is determined by their configuration and conformational freedom. The model has been validated by the oxidation of several complex natural products, including two steroids. From a synthesis perspective, the model predicts whether a natural product comprising multiple hydroxy groups is a suitable substrate for site-selective palladium-catalyzed oxidation.

Nature Communications, Published online: 26 May 2023; doi:10.1038/s41467-023-38888-6

The sustainable synthesis of cyclohexanone oxime, the precursor of nylon-6, without toxic SO2 or H2O2 usage is desirable. Here, the electrosynthesis of cyclohexanone oxime from nitrite and cyclohexanone under ambient conditions is reported.

Nature Communications, Published online: 22 May 2023; doi:10.1038/s41467-023-38702-3

Accessing saturated stereogenic centers by asymmetric alkyl-alkyl formation is attractive yet challenging. Here, the authors develop a Ni-catalysed cross-coupling reaction of two alkyl halides enabled by the in-situ formation of alkyl zinc from one alkyl halide.

Radical-based convergent paired electrolysis, which is driven by inexpensive electricity, is a green and unique approach to otherwise challenging redox-neutral reactions. The difficulty associated with the technique is imposed by the fleeting nature of radicals and the gap between electrodes. This concept article introduces recent state-of-the-art advances in this field and discusses how to overcome the obstacles.

Abstract

Electrochemistry offers a sustainable platform for discovering reactions involving single-electron transfer (SET) that generates highly reactive and synthetically versatile radical species. Compared with photochemistry similarly specializing in SET which requires expensive photocatalysts, electrochemistry employs low-cost electricity to drive the electron flow. Paired electrolysis makes use of both half-reactions, thus obviating the need for sacrificial reactions and maximizing the atom and energy economy. In convergent paired electrolysis, anodic oxidation and cathodic reduction occur simultaneously to generate two intermediates, which are then coupled to furnish the product. It represents a distinctive approach to challenging redox-neutral reactions. However, the gap between the two electrodes makes it hard for a reactive intermediate to come across the other coupling partner. This concept article summarizes recent state-of-the-art advances on radical-based convergent paired electrolysis, which adopted different strategies to overcome the difficulty.

A method to oxidize toluene selectively to benzaldehyde photochemically is described. A series of copper(I) complexes with different ligands were applied in combination with [Ru(bipy)₃](PF₆)₂ and dioxygen as the oxidant. The copper(II) complexes obtained after oxidation were photochemically reduced to the starting copper(I) species, and the process can be repeated continuously.

Abstract

A method is described to photochemically oxidize toluene selectively to benzaldehyde, an essential compound in the chemical industry. Copper(I) complexes with different ligands were applied in combination with [Ru(bipy)₃](PF₆)₂ and dioxygen as the oxidant. As a result, a “dioxygen adduct” copper complex, for example, a peroxido complex, is formed as the active species. The copper(II) complex obtained after oxidation can be photochemically reduced to the starting copper(I) species, and the process can be repeated continuously. The ligand tris(2-methylpyridyl)amine (tmpa) led to the highest conversion rates.

Charting the reaction space around a known Multicomponent Reaction (MCR) allows the development of new processes. In this way, a detailed study of the parameters involved in the Orru transformation leads to the generation of alternative connectivities featuring diversely substituted imidazolones, including GFP (Green Fluorescent Protein) chromophores, coelenterazine derivatives, natural products, kinase inhibitors, and bioprobes.

Abstract

Charting the chemical reaction space around the combination of carbonyls, amines, and isocyanoacetates allows the description of new multicomponent processes leading to a variety of unsaturated imidazolone scaffolds. The resulting compounds display the chromophore of the green fluorescent protein and the core of the natural product coelenterazine. Despite the competitive nature of the pathways involved, general protocols provide selective access to the desired chemotypes. Moreover, we describe unprecedented reactivity at the C-2 position of the imidazolone core to directly afford C, S, and N-derivatives featuring natural products (e.g. leucettamines), potent kinase inhibitors, and fluorescent probes with suitable optical and biological profiles.

BASHY dyes, such as the one drawn in the foreground, are prepared in a multicomponent reaction. This is symbolized by the background, which shows part of a beach that is made of sea-washed stones and which is located in the North of Portugal (Praia de Belinho). The BASHY dyes discussed in the Research Article by P. M. P. Gois, U. Pischel and co-workers (DOI: 10.1002/chem.202300579) show several photophysical features such as fluorescence, intramolecular charge transfer (ICT), and photoinduced electron transfer (PeT), which jointly orchestrate the function of the dye.

Electrochemistry is a valuable tool used by modern synthetic chemists who use electricity to facilitate redox reactions. In this image, created by Karrar Nadhom, the dragon provides the electrical surge to create a reaction between sodium nitrite and a secondary amine, which are fused to form the N-nitroso product. Despite dragons being extinct in most parts of the world, the title reaction is an ecologically green process, as indicated by the colour of the dragon. More information can be found in the Research Article by T. Wirth and co-workers (DOI: 10.1002/chem.202300957).

A chirality transfer strategy was established to access enantioenriched boron C,N-chelates stereogenic only at the B-atom. First, a library of chiral boron O,N-complexes was synthesized in diastereoselective fashion. The generated stereoinformation at boron was then transferred via the ate-complex into the boron C,N-chelates.Twitter affiliations: @LaschatGroup, @YStoeckl

Abstract

Molecules stereogenic only at tetrahedral boron atoms show great promise for applications, for example as chiroptical materials, but are scarcely investigated due to their synthetic challenge. Hence, this study reports a two-step synthesis of enantioenriched boron C,N-chelates. First, the diastereoselective complexation of alkyl/aryl borinates with chiral aminoalcohols furnished boron stereogenic heterocycles in up to 86 % yield and d.r. >98 : 2. Treatment of these O,N-complexes with chelate nucleophiles was surmised to transfer the stereoinformation via the ate-complex into the C,N-products. This chirality transfer succeeded by substitution of the O,N-chelates with lithiated phenyl pyridine to give boron stereogenic C,N-chelates in up to 84 % yield and e.r. up to 97 : 3. The chiral aminoalcohol ligands could be recovered after isolation of the C,N-chelates. The chirality transfer tolerated alkyl, alkynyl and (hetero-)aryl moieties at boron and could be further extended by post-modification: transformations such as catalytic hydrogenations or sequential deprotonation/electrophilic trapping were feasible while maintaining the stereochemical integrity of the C,N-chelates. Structural aspects of the boron chelates were studied by variable temperature NMR and X-ray diffraction.