Marnix van der Kolk

The Suzuki-Miyaura cross-coupling reaction is plagued by protodeboronation, an undesirable side reaction with water that consumes the boronic acid derivatives required for the cross-coupling reaction. Meticulous mechanistic studies have previously established protodeboronation to be highly sensitive to the nature of the boronic reagent and reaction conditions. Particularly, the presence of bases, which are essential for the Suzuki-Miyaura coupling, is known to catalyse protodeboronation. However, protodeboronation catalysed by palladium-phosphine complexes, the benchmark catalyst system for Suzuki-Miyaura cross-coupling, has been largely overlooked. We demonstrate, using automated high-throughput experimentation, comprehensive computational mechanistic analyses and kinetic modelling, that protodeboronation is accelerated by palladium(II) complexes bound to bulky phosphine ligands. While sterically hindered ligands are typically used to facilitate difficult cross-couplings, these ligands can instead paradoxically impede cross-coupling product formation, requiring careful and judicious consideration when choosing ligands for Suzuki-Miyaura cross-couplings.

Organic electrochemical synthesis may be combined with continuous flow and automation technology. Here, the authors highlight the benefits if such chemical engineering approaches along with technology and software directions taking organic chemistry into the future.

In an era where digital communication dominates the social interactions of adolescents and young adults, understanding the dynamics of these interactions is important. Our study explored how social norms within group chats influence expected cyber-aggressive behaviors.

Nature, Published online: 01 August 2024; doi:10.1038/d41586-024-02511-5

A player wins by racking up more citations than the competition, even if that means engaging in a little light plagiarism.

Small (NHC)-stabilized Au nanoparticles 2.52 nm in size and nearly monodisperse can be readily and reproducibly synthesized starting from a triimidazotriazine functionalized by N-alkylation with benzylbromide. Subsequent ionic exchange with [AuCl4]- and reduction of the resulting imidazolium tetrachloroaurate affords new (NHC)-protected Au nanoparticles. These nanoparticles can be readily adsorbed on commercial titania affording a catalyst of exceptional activity and selectivity in the reduction of nitrobenzene to aniline at room temperature and ambient pressure.

The nickel(0) complex [Ni(iPrPN)(COD)] (iPrPN = 2-[(N-diisopropylphosphino)methylamino]pyridine, COD = 1,5-cyclooctadiene) has been found an efficient precatalyst for the hydrodefluorination of pyridines employing HBPin. Substituted 2,6-difluoropyridines were doubly hydrodefluorinated selectively at the 2 and 6 positions at room tem-perature employing 5 mol% of catalyst loading. Mechanistic studies for the hydrodefluorination of 2,6-difluoropyridine allowed to identify COD decoordination followed by C-F activation of the fluorinated pyridine as the catalyst entry pathway to the cycle and the [Ni(iPrPN)(COD)] complex as the catalyst resting-state.

Abstract

Organic electrosynthesis has become a green, efficient and sustainable alternative to traditional organic transformation for the redox reactions. In this connection, indirect electrolysis employing redox mediators is attaining increasing significance as it offers a chance to improve reaction selectivity and avoids the over-oxidation/reduction issues encountered in direct electrolysis. Triarylamines and triarylimidazoles, as representative organic molecular mediators, have attracted widespread attention in recent years due to the advantages of well-defined easy structural modification and tunable redox ability. Hence, in this minireview, the recent growth of triarylamine and triarylimidazole derivatives mediated electrochemical oxidation reactions were presented, highlighting the structural optimization, electrochemical performance and reaction mechanism of these organic mediators. Moreover, the photocatalytic and photoelectrocatalytic cases with these molecular mediators were also highlighted. To conclude, the current challenges and future prospects of this field are also discussed.

Type 2 diabetes mellitus is a rapidly growing concern in developing countries. The economic burden on patients in these regions is substantial, exacerbated by limited healthcare infrastructure.

Publication date: 1 December 2024

Source: Catalysis Today, Volume 442

Author(s): Qian Qiang, Huamei Yang, Wentao Su, Haiyan He, Shenglong Tian, Changzhi Li, Tao Zhang

We explore the challenges and insights of segmenting and releasing selected annotated instance segmentation sub-volumes of a large-scale CT dataset of a historic aircraft. Discover our decision-making process, reasons for the release, and concerns about sharing this information publicly.

Nature Synthesis, Published online: 21 June 2024; doi:10.1038/s44160-024-00578-6

C–F bond formation using transition-metal catalysis is a challenge owing to the high energy barrier associated with reductive elimination. Now the direct β-C(sp3)–H fluorination of aliphatic carboxylic acids with a broad substrate scope is reported, using rational oxidant design to facilitate the reductive elimination step.

Nature Synthesis, Published online: 20 June 2024; doi:10.1038/s44160-024-00568-8

CO electroreduction is a promising carbonate-free approach to produce ethylene, but suffers from limited selectivity and low energy efficiency. By modifying copper with a strong electron acceptor, 7,7,8,8-tetracyanoquinodimethane, the water dissociation step is accelerated, leading to excellent ethylene selectivity and full-cell energy efficiency in CO electroreduction.

Polyhydroxyurethane (PHU) thermosets are the most promising isocyanate-free substitutes to polyurethane ones when targeting the main applications of the PU business (coatings, adhesives, foams). However, the curing of their solvent-free formulations at near room temperatures is often very slow and requires the utilization of organocatalysts, limiting the large-scale deployment of the technology. Herein, we study the impact of water, introduced as an additive (2 to 10 wt.%), on the crosslinking rate of common solvent-free thermosetting PHU formulations composed of a polycyclic carbonate and a diamine. Rheology measurements, using a multi-frequency approach, indicate that even very small amounts of water (< 5 wt.%) impressively shorten gel times, by up to 5 folds at 40 °C. The multi-frequency methodology highlights for the first time the strong interactions of water with the growing PHU network during the crosslinking reaction. It suggests that water breaks down the multiple intra-/inter-molecular H-bond interactions within the PHU clusters, consequently enhancing the molecular mobility and delaying the vitrification (hydroplasticization), both phenomena contributing to accelerate the crosslinking rate. On top of that, through a combination of model reactions and computational calculations, we demonstrate that water is an actual catalyst of the cyclic carbonate aminolysis. Eventually, thanks to its multifaceted role, water can efficiently substitute the organocatalysts (e.g. TBD, DBU) usually required to cure PHU formulations at near ambient temperature. This work demonstrates that the use of additive amounts of water in solvent-free formulations is a cost-effective, non-toxic, and robust solution to accelerate the production of PHU materials, free of any organocatalyst. It offers promising prospects for the deployment of PHU-based materials requiring mild processing conditions.

Nature, Published online: 17 June 2024; doi:10.1038/d41586-024-02029-w

A steadily growing toolbox is giving researchers the ability to monitor and measure the physical forces that shape embryonic development.