Robby Vroemans

Under mild conditions: A redox-neutral and base-free protocol for the directed ruthenium-catalyzed C−H aminocarbonylation is developed through high-throughput experimentation. The mild conditions allowed the introduction of privileged amide moieties to a wide range of anilides bearing various substitution patterns and different weakly Lewis basic directing groups.

Abstract

Introducing amide functional groups under mild conditions has growing importance owing to the prevalence of such moiety in biologically active molecules. Herein, we disclose a mild protocol for the directed ruthenium-catalyzed C−H aminocarbonylation with isocyanates as the amidating agents developed through high-throughput experimentation (HTE). The redox-neutral and base-free reaction is guided by weakly Lewis basic functional groups, including anilides, lactams and carbamates to access anthranilamide derivatives. The synthetic utility of this transformation is reflected by large-scale synthesis and late-stage functionalization.

Simple heating of muconic acid in water at high temperature in an autoclave under autogenic pressure provides levulinic acid in high yield, as described by Bert U. W. Maes et al. in their Communication (e202309597). The method can also be applied to make substituted levulinic acids from the corresponding muconic acids. Lignin oil rich in propylguaiacol obtained from pine sawdust has been successfully transformed into 3-propyllevulinic acid.

Nature Catalysis, Published online: 21 September 2023; doi:10.1038/s41929-023-01029-9

Herein, an operationally simple protocol for the ex-situ generation of the toxic and volatile disulfide, CF₃SSCF₃, from the readily available and cost-efficient Langlois reagent is reported. Among the trifluoromethythiolations reaction studied, application of this disulfide in a Cu-catalyzed coupling with aryl boronic acids is disclosed, showing good to excellent yields of trifluoromethylthio-substituted aryl products.

Abstract

Herein, a convenient and operationally simple protocol for the ex-situ generation of bis(trifluoromethyl)disulfide from the readily available and commercial Langlois reagent is reported. The one-step synthesis of the toxic and volatile CF₃SSCF₃ is performed in a two-chamber reactor with simple PPh₃ and N-bromosuccinimide as the activator, allowing for the safe handling and tandem utilization in direct trifluoromethylthiolation reactions. The versatility of the ex-situ generated CF₃SSCF₃ is demonstrated in known electrophilic, nucleophilic, and a radical trifluoromethylthiolation reactions. Furthermore, the application of the CF₃SSCF₃ in a copper-catalyzed cross-coupling with boronic acids is disclosed, showing good to excellent yields of trifluoromethyl-substituted aryl products, including pharmaceutically relevant molecules.

Sulfur-centered radicals have a key role in a plethora of synthetic transformations, whose scope is ever-expanding thanks to visible light photocatalysis. The current review focuses on those transformations involving isocyanides and S-centered radicals and aims to highlight the chemical space accessible and the mechanistic rational underpinning current and future developments.

Abstract

Sulfur-centered radicals have a key role in a plethora of synthetic organic transformations, whose scope has been further expanded thanks to the possibility to generate such species under visible light photocatalytic conditions. This review focuses on those transformations involving isocyanides and sulfur-centered radicals with the aim to highlight the chemical space accessible, both in terms of complexity and diversity, and the mechanistic rational underpinning the current and future development of such chemical methodologies.

Nature, Published online: 20 September 2023; doi:10.1038/s41586-023-06529-z

Nature Reviews Chemistry, Published online: 20 September 2023; doi:10.1038/s41570-023-00534-6

Nature, Published online: 14 September 2023; doi:10.1038/d41586-023-02886-x

The local structures of Ni single-atom catalysts were regulated by adjusting carbonization temperature of their precursors. The oxidation state, total coordination number, and bond length of the metal center decrease with the increase of the carbonization temperature. The relationship between structure and performance was explored. The structure after regulation could promote the adsorption of CO₂ and improve electrocatalytic CO₂ reduction activity.

Abstract

Single-atom catalysts (SACs) have the unique coordination environment and electronic structure due to the quantum size effect, which plays an essential role in facilitating catalytic reactions. However, due to the limited understanding of the formation mechanism of single atoms, achieving the modulation of the local atomic structure of SACs is still difficult and challenging. Herein, we have prepared a series of Ni SACs loaded on nitrogen-doped carbon substrates with different parameters using a dissolution-and-carbonization method to systematically investigate the effect of temperature on the structure of the SACs. The results of characterization and electrochemical measurements are analyzed to reveal the uniform law between temperature and the metal loading, bond length, coordination number, valence state and CO₂ reduction performance, showing the feasibility of controlling the structure of SACs through temperature to regulate the catalytic performance. This is important for the understanding of catalytic reaction mechanisms and the design of efficient catalysts.

Atomically dispersed N-coordinated Co/Cu dual-metal sites were designed and constructed for improved dehydrogenation of formic acid. In situ spectroscopy and theoretical calculations revealed that the Co/Cu dual-metal sites synergistically improve the performance of the optimized catalytic system. The presented work describes catalysts based on low-cost earth abundant dual-metal sites as promising candidates for H₂ storage and delivery.

Abstract

The development of practical materials for (de)hydrogenation reactions is a prerequisite for the launch of a sustainable hydrogen economy. Herein, we present the design and construction of an atomically dispersed dual-metal site Co/Cu−N−C catalyst allowing significantly improved dehydrogenation of formic acid, which is available from carbon dioxide and green hydrogen. The active catalyst centers consist of specific CoCuN₆ moieties with double-N-bridged adjacent metal-N₄ clusters decorated on a nitrogen-doped carbon support. At optimal conditions the dehydrogenation performance of the nanostructured material (mass activity 77.7 L ⋅ g_metal ⁻¹ ⋅ h⁻¹) is up to 40 times higher compared to commercial 5 % Pd/C. In situ spectroscopic and kinetic isotope effect experiments indicate that Co/Cu−N−C promoted formic acid dehydrogenation follows the so-called formate pathway with the C−H dissociation of HCOO* as the rate-determining step. Theoretical calculations reveal that Cu in the CoCuN₆ moiety synergistically contributes to the adsorption of intermediate HCOO* and raises the d-band center of Co to favor HCOO* activation and thereby lower the reaction energy barrier.

Abstract

Organic thermally activated delayed fluorescence (TADF) materials have been widely investigated due to their impressive electronic properties and applied potential for the third generation of organic light-emitting diodes (OLED). We present organic TADF material (4BGIPN) based on the strained benzoguanidine donor and compare it with the benchmark carbazole-based material (4CzIPN). Extended π-conjugation in 4BGIPN material results in yellow-green luminescence at 512 nm with a fast radiative rate of 5.5 × 10⁻⁵ s⁻¹ and a photoluminescence quantum yield of 46% in methylcyclohexane solution. Such a nitrogen-rich 4BGIPN material has a significantly stabilized highest occupied molecular orbital (HOMO) at −6.4 eV while the lowest unoccupied molecular orbital (LUMO) at −4.0 eV, indicating potential suitability for application as the electron transport layer or TADF class III emitter in OLEDs.

Beilstein J. Org. Chem. 2023, 19, 1289–1298. doi:10.3762/bjoc.19.95

The cover depicts the generation of fluoroalkyl radical species by photoredox catalysis from chiral and structurally diverse fluoroalkyl sulfoximine compounds. See the Personal Account by T. Koike (DOI: 10.1002/tcr.202300032).

Synlett
DOI: 10.1055/a-2122-8508

The reduction of nitro compounds is one of the fundamental organic transformations and ascertain wide applicability in industrial chemistry, synthesis of valuable scaffolds, fine chemical synthesis, as well as environmental applicability for decontamination process. The transformation involves the conversion of nitro compounds into valuable scaffolds including amino, nitroso, hydroxyl amines, azo, and hydrazo compounds. Conventional approaches for the reduction of nitro compounds involves the environmentally harmful stoichiometric reagents, high-boiling reaction media, tedious processes, and harsh reaction conditions with high temperature and pressure. Additionally, the selectivity always remains a serious concern associated with the process due to the possibilities of several stable intermediate formation in the reaction pathway of reduction of nitro compounds. Nitro compounds are also of serious environmental concerns being a part of most harmful and high-priority classes of pollutants mainly released from industrial effluents, agricultural waste, and human sewage. A simple degradation of these pollutants bearing nitro group just removes the pollutants, however, the selective reduction of nitro group to valuable functionalities as mentioned above provides the industrially important scaffolds. With the advent of photocatalytic organic transformation, most of the scientific fraternity working in the area of organic synthesis, catalysis, and environmental decontaminations are utilizing the clean, green, low-temperature, energy and cost-effective, sustainable processes for the reduction of nitro compounds to access valuable scaffolds. Nowadays a lot of mechanistic developments in the field ease the processes for the developments of such highly valuable organic transformations. Herein, the present Account is focused on the recent developments in the photocatalytic reduction of nitro compounds to valuable scaffolds.1 Introduction2 Reduction of Nitro Compounds2.1 Conventional Approaches for Reduction of Nitro Compounds2.2 General Photocatalytic Mechanism3 Mechanistic Pathways: Electrochemical, Conventional and Photocatalytic Approaches3.1 Mechanism of Electrochemical Reduction of Nitroarene3.2 Conventional Reduction Mechanism of Nitroarenes3.3 General Photocatalytic Reduction Mechanism of Nitroarenes4 Photocatalytic Reduction of Nitro Compounds to Valuable Scaffolds4.1 Reduction of Nitro Compounds to Corresponding Amines4.2 Reduction of Nitro Compounds to Azo Compounds4.3 Reduction of Nitro Compounds to Azoxy Compounds4.4 Reduction of Nitro Compounds to Nitroso Compounds4.5 Reduction of Nitro Compounds to Hydroxyl Amines5 Future Perspective6 Conclusion
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Transition-metal-catalyzed addition of organosulfur compounds to carbon-carbon unsaturated bonds has been considered as one of the challenging reactions due to the catalyst poisons. Recently, novel systems have been investigated to suppress the catalyst poisons. This article highlights the pioneering studies on the catalytic addition of organosulfur compounds to alkynes and alkenes and describes their catalysis and catalyst poisons.

Abstract

The addition of heteroatom compounds to alkynes and alkenes is an atom-efficient method of carbon-heteroatom bond formation and is widely used as a fundamental synthetic method for the construction of functional molecules. Nevertheless, examples of transition-metal-catalyzed addition reactions of group 16 heteroatom compounds to carbon-carbon unsaturated bonds have been limited due to the widespread belief that organic sulfur and selenium compounds are representative catalyst poisons. In recent decades, however, several seminal catalytic reactions of sulfur compounds have been developed, providing important insights into catalysis and poisons. Therefore, this paper focuses on the transition-metal-catalyzed addition of organosulfur compounds to alkynes and alkenes, gains comprehensive insights into the catalysis and catalyst poisons, and proposes concepts for the development of transition-metal-catalyzed reactions of group 16 heteroatom compounds.

Nature Communications, Published online: 02 September 2023; doi:10.1038/s41467-023-40197-x

Nature Chemistry, Published online: 31 August 2023; doi:10.1038/s41557-023-01312-z