ceverelst

The Front Cover depicts the process of chemically upgrading the renewable, biomass-derived levulinic acid (LA) by simply mixing it with l-arginine. LA is known as a platform compound that provides a conversion pathway from biomass towards bio-jet fuels. This method provides full regioselectivity to one product, proceeds with mild heating, and requires the presence of only one renewable organocatalyst with no additional solvent or reaction matrix needed. More information can be found in the Research Article by T. Neal and co-workers. Image by Jennifer F. Neal.

Publication date: Available online 16 May 2024

Source: Chem Catalysis

Author(s): Jean-Philippe Tessonnier

The rule will phase out all consumer and most industrial uses of the solvent within 2 years

In this study, we demonstrated the first example for the asymmetric copolymerization of various meso-epoxide with isocyanates toward the synthesis of chiral polymers with unique nitrogen functionality. Intramolecular bimetallic coordination strategies provided completely alternating copolymers with high carbamate unit content (up to 94 %) and high enantioselectivity (up to 94 % ee).

Abstract

The introduction of nitrogen-containing functional groups to chiral polymer backbones enables the tailoring of physical properties and offers opportunities for further post-polymerization modification. However, the substrate scope of such polymers is extremely limited because monomers having nitrogen-containing groups can change coordination state with respect to the metal centers, thus decreasing the activity and enantioselectivity and even poisoning the catalyst completely. In this paper, we report our attempts to carry out the asymmetric copolymerization of meso-epoxide with highly reactive isocyanates. In particular, we found that biphenol-linked bimetallic Co(III) complexes with multiple chiral centers are very efficient in catalyzing this asymmetric copolymerization reaction, affording optically active polyurethanes with a completely alternating nature and a high enantioselectivity of up to 94 % ee. Crucially, we identified that the steric hindrance at the phenolate ortho position of the ligand strongly influences the catalytic activity and product enantioselectivity. In addition, density functional theory calculations revealed that the highly sterically bulky substituents change the mechanism from bimetallic to monometallic, and result in the unexpected inversion of the chiral induction direction. Moreover, the high stereoregularity of the produced polyurethanes enhances their thermal stability, and they can be selectively decomposed into oxazolidinones. This study offers a versatile methodology for the synthesis of chiral polymers containing nitrogen functionalities.

Nature, Published online: 25 April 2024; doi:10.1038/d41586-024-01246-7

By joining a collecting society, researchers can ensure they are paid when copyrighted book content and papers are reproduced.

We present a concept inspired by playing with blocks, in which it is possible to construct various objects from segments (blocks) of different sizes and lengths. An attempt is made to explain the mechanism of coupling reaction in a ball mill in the presence of cesium carbonate. The usefulness of the method in the synthesis of oligopeptides has been proven.

Abstract

We report an idea for the synthesis of oligopeptides using a solvent-free ball milling approach. Our concept is inspired by block play, in which it is possible to construct different objects using segments (blocks) of different sizes and lengths. We prove that by having a library of short peptides and employing the ball mill mechanosynthesis (BMMS) method, peptides can be easily coupled to form different oligopeptides with the desired functional and biological properties. Optimizing the BMMS process we found that the best yields we obtained when TBTU and cesium carbonate were used as reagents. The role of Cs₂CO₃ in the coupling mechanism was followed on each stage of synthesis by ¹H, ¹³C and ¹³³Cs NMR employing Magic Angle Spinning (MAS) techniques. It was found that cesium carbonate acts not only as a base but is also responsible for the activation of substrates and intermediates. The unique information about the BMMS mechanism is based on the analysis of 2D NMR data. The power of BMMS is proved by the example of different peptide combinations, 2+2, 3+2, 4+2, 5+2 and 4+4. The tetra-, penta-, hexa-, hepta- and octapeptides obtained under this project were fully characterized by MS and NMR techniques.

One-Factor-At-a-Time (OFAT) approach and the multivariate approach were adopted for the optimization of fructose and inulin one-pot ethanolysis, respectively, allowing to systematically elucidate the role of key reaction parameters (temperature, H₂SO₄ and inulin loadings, reaction time) and aiming at the maximisation of EL yield and concentration while minimising the formation of by-products, such as diethyl ether and solid char.

Abstract

Alkyl levulinates (ALs) are strategic compounds for the development of sustainable energy transition. In this regard, the direct alcoholysis of fructose and inulin for the selective ethyl levulinate (EL) production was investigated with a One-Factor-At-a-Time (OFAT) approach employing diluted H₂SO₄ as catalyst to clarify the role of the main reaction parameters (substrate and acid loadings, temperature, reaction time). The OFAT investigation on fructose ethanolysis allowed to reach the EL yield of 91.5 mol%. The inulin ethanolysis was then optimized adopting the multivariate approach based on the Response Surface Methodology (RSM), which highlighted the interplay of the reaction parameters on the selective EL production. This allowed to identify the optimal conditions to reach the highest EL yield (up to 89.3 mol%) and also those which ensured the highest EL concentration, adopting a substrate loading (14 wt%) higher than the majority ones reported in the literature according to the high gravity approach, and the lowest diethyl ether (DEE) by-product yield. The DEE formation is scarcely investigated in the literature, but it can negatively influence the alcoholysis process, thus it was considered in this work. Moreover, the humin solid residue was deeply characterized to envisage its possible applications, under a circular economy perspective.

Nature, Published online: 16 April 2024; doi:10.1038/d41586-024-01012-9

An ambitious investigation has analysed discourse on eight social-media platforms, covering a vast array of topics and spanning several decades. It reveals that online conversations increase in toxicity as they get longer — and that this behaviour persists despite shifts in platforms’ business models, technological advances and societal norms.

Chemistry has the potential to drive global sustainability efforts, but how to ensure its optimal impact is not always obvious. Through analysis of green, circular, and sustainable chemistry concepts, this Scientific Perspective identifies unified triple E priorities, covering environmental, economic, and equity pillars, and categorizes associated metrics. Case studies illustrate how these can be used to guide research and decisions.

Abstract

Chemistry, a vital tool for sustainable development, faces a challenge due to the lack of clear guidance on actionable steps, hindering the optimal adoption of sustainability practices across its diverse facets from discovery to implementation. This Scientific Perspective explores established frameworks and principles, proposing a conciliated set of triple E priorities anchored on Environmental, Economic, and Equity pillars for research and decision making. We outline associated metrics, crucial for quantifying impacts, classifying them according to their focus areas and scales tackled. Emphasizing catalysis as a key driver of sustainable synthesis of chemicals and materials, we exemplify how triple E priorities can practically guide the development and implementation of processes from renewables conversions to complex customized products. We summarize by proposing a roadmap for the community aimed at raising awareness, fostering academia–industry collaboration, and stimulating further advances in sustainable chemical technologies across their broad scope.

In the last decades, numerous efforts have been made to replace metal catalysts with cheaper and earth-abundant alternatives or the complete exclusion of metals in cross-coupling reactions, maintaining high efficiency of the target transformation. However, follow-up studies often revealed the role of metal impurities in the catalytic process. Thus, active metal impurities lead to mechanistic misinterpretations, could initiate erroneous research directives, and can lead to severe reproducibility problems. Milestone precedents of impurity effect in cross-coupling reactions are well documented in the literature. Interestingly, this fallacy has occurred repeatedly over the years due to the lack of thorough mechanistic studies and the appropriate research study scheme for identifying the impurity effect. Herein, we propose a guideline elucidating the real catalyst of future catalytic transformations that could eliminate mechanistic misinterpretation and help exclude the role of impurities in novel catalytic processes. Although this guideline mainly focuses on problems related to trace transition metals, it also offers the base for more general catalyst research.

New furan, carvone and limonene-based carbamates have been synthesized with high regioselectivity under solvent-free and mild reaction conditions. Moreover, a detailed study on the reaction conditions allowed for the drastic reduction of the TBD loading with almost no effect on the regioselectivity.

Abstract

The regioselective synthesis of carbamates from bio-derived cyclic carbonates and amines by using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as an organocatalyst is reported. This methodology led to the preparation of a wide range of bio-sourced hydroxyurethanes from furan-, carvone- and limonene-based scaffolds under solvent-free and mild reaction conditions. Moreover, a comprehensive analysis of the process allowed us to optimize the catalyst loading with little or no impact on the process regioselectivity.

Nature, Published online: 27 March 2024; doi:10.1038/d41586-024-00951-7

Whether for April Fools’ Day or year-round, practical jokes allow scientists to tap into creative thinking while building group camaraderie.

Synlett
DOI: 10.1055/a-2283-5829

Azo compounds with a high density, high enthalpy, and excellent detonation performance have received increasing research attention. The conventional method of chemical dehydrogenation that is used to form azo compounds involves the use of strong oxidants, resulting in environmental pollution. Electrochemical organic synthesis is considered an old method and a new technology. In this work, azofurazan tetrazole {H2AzFT; 5,5′-[diazene-1,2-diylbis(1,2,5-oxadiazole-4,3-diyl)]bis-1H-tetrazole} and azofurazan hydroxytetrazole (H2AzFTO) were synthesized by a green and efficient electrochemical dehydrogenation coupling of 5-(4-aminofurazan-3-yl)-1H-tetrazole and 5-(4-aminofurazan-3-yl)-1-hydroxytetrazole, respectively. The structures of H2AzFT and (NH4)2AzFTO were fully characterized by infrared spectroscopy, nuclear magnetic resonance, and elemental analysis, and their thermal stabilities were determined by differential thermal analysis.
[...]

Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
Table of contents  |  Abstract  |  Full text