Robby Vroemans

Nature, Published online: 23 November 2022; doi:10.1038/d41586-022-03791-5

All data should get checked, but not every article needs an expert.

Visible-light-mediated oxyarylation and hydroarylation of alkenes with aryl halides using formate salts as the reductant and hydrogen source under ambient conditions were developed. The protocol represents a rare catalyst-free example of the realization of such transformations.

Abstract

Visible-light-mediated oxyarylation and hydroarylation of alkenes with aryl halides using formate salts as the reductant and hydrogen source under ambient conditions were developed. These protocols represent rare catalyst-free examples of the realization of such transformations. Using styrenes as substrates, oxyarylation could occur smoothly. Whereas, hydroarylation proceeds employing electron deficient alkenes. Moreover, dehalogenation proceeds successfully in the absence of alkenes. We expected that this method could provide a valuable strategy for the functionalization of aryl halides.

Nature Materials, Published online: 22 November 2022; doi:10.1038/s41563-022-01427-7

Size matters

Nature Reviews Chemistry, Published online: 21 November 2022; doi:10.1038/s41570-022-00442-1

Mechanochemistry is the science of inducing a chemical reaction through the application of mechanical force. This Perspective focuses on combining traditional mechanochemistry with different energy inputs — heat, light, sound or electrical impulses — to advance mechanochemical synthesis.

Cobalt nanoparticles embedded in three-dimensional network of nitrogen-doped graphene exhibited high catalytic activity for the cleavage of β-O-4 linkage in lignin under moderate condition without any additive.

Abstract

The cleavage of β-O-4 linkage in lignin is one of the key steps for oxidative conversion of lignin to low-molecular-weight aromatics. Herein, Co nanoparticles embedded in three-dimensional network of nitrogen-doped graphene (Co/NG@3DNG-X) were prepared through an immersion-pyrolysis procedure, in which X denotes the pyrolysis temperature. The detailed characterization of Co/NG@3DNG-X shows that the Co nanoparticles are coated with a few layers of nitrogen-doped graphene (NG) sheets that are further embedded in 3DNG matrix. The catalytic activities of the Co/NG@3DNG-X for the oxidative cleavage of β-O-4 linkage in lignin model compounds with O₂ as oxidant are explored. It is demonstrated that catalytic activities of as-prepared Co/NG@3DNG-X can be tuned by varying the pyrolysis condition, and the Co/NG@3DNG-900 shows the highest catalytic activity, which is attributed to the enriched Co-N_x species, the strong surface basicity, the high specific surface and the mesoporous motif of 3DNG network. More pronouncedly, the Co/NG@3DNG-900 can also effectively catalyze the oxidative cleavage of organosolv lignin, generating certain monomeric aromatics. Additionally, the intrinsic magnetic property of Co nanoparticles makes the Co/NG@3DNG-X be easily recovered from the reaction mixture, and the as-coated thin NG layer can protect Co nanoparticle from oxidation condition, which putting together afford the Co/NG@3DNG-X with good reusability and stability.

Nature Synthesis, Published online: 21 November 2022; doi:10.1038/s44160-022-00200-7

The Paternò–Büchi reaction is a useful approach in organic synthesis to prepare oxetanes. Understanding the mechanism of this reaction is required for the prediction and control of the diastereoselectivity of the products.

Blue-to-UVB photon upconversion (UC) enabled by a benzene-based annihilator is presented for the first time. The annihilator's unprecedented singlet-excited energy of 4.15 eV was successfully employed to activate inert carbonyls via a subsequent FRET energy transfer. This UC-FRET reaction scheme was directly monitored by laser techniques and exploited in lab-scale NMR experiments demonstrating its potential in light-to-chemical energy conversion.

Abstract

Several energy-demanding photoreactions require harsh UV light from inefficient light sources. The conversion of low-energy visible light to high-energy singlet states via triplet-triplet annihilation upconversion (TTA-UC) could offer a solution for driving such reactions under mild conditions. We present the first annihilator with an emission maximum in the UVB region that, combined with an organic sensitizer, is suitable for blue-to-UVB upconversion. The annihilator singlet was successfully employed as an energy donor in subsequent FRET activations of aliphatic carbonyls. This hitherto unreported UC-FRET reaction sequence was directly monitored using laser spectroscopy and applied to mechanistic irradiation experiments demonstrating the feasibility of Norrish chemistry. Our results provide clear evidence for a novel blue light-driven substrate or solvent activation strategy, which is important in the context of developing more sustainable light-to-chemical energy conversion systems.

Publication date: 1 February 2023

Source: Coordination Chemistry Reviews, Volume 476

Author(s): Muhammad Ashraf, Muhammad Sohail Ahmad, Yusuke Inomata, Nisar Ullah, Muhammad Nawaz Tahir, Tetsuya Kida

Synthesis
DOI: 10.1055/s-0042-1751382

A convenient method for the synthesis of 2-azido-3-arylpropanoic acids via the Meerwein halogenoarylation reaction of acrylic acid esters with diazonium salts, subsequent nucleophilic substitution of the halogen by an azide, and saponification is developed. The newly formed 2-azido-3-arylpropanoic acids react under the conditions of non-catalytic four-component Ugi reactions, leading to the formation of α-azidoamides in good yields. The use of propargylamine as the amine component allows the formation of Ugi adducts with azide and acetylene motifs ready for intramolecular 1,3-dipolar Huisgen cycloaddition to give the [1,2,3]triazolo[1,5-a]pyrazine annulated system. The Ugi reaction is found to give 2-azido-3-aryl-N-(2-oxo-1,2-disubstituted ethyl)-N-(prop-2-yn-1-yl)propanamides at room temperature without azide–alkyne cycloaddition. These dipeptides are converted into 4,5-dihydro[1,2,3]triazolo[1,5-a]pyrazin-6(7H)-ones in near quantitative yields by heating in toluene. However, when the Ugi reaction is carried out by heating, it results in a one-pot Ugi–Huisgen tandem reaction leading to 4,5-dihydro[1,2,3]triazolo[1,5-a]pyrazin-6(7H)-ones in excellent yields. Moreover, the possibility of the incorporation of a bromovinyl fragment (the synthetic equivalent of an acetylene fragment) via the aldehyde component of the Ugi reaction is demonstrated in an alternative preparation of the [1,2,3]triazolo[1,5-a]pyrazine system.
[...]

Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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

Review summarizes the catalytic reactions via the dual catalysis of organoboron compounds and another catalyst, which showed specific catalytic activity in organic transformations.

Abstract

In recent years, organoboron compounds has attracted much attention due to their unique chemical properties. In this Review, we summarize catalytic reactions via the dual catalysis of boron and another catalyst, which showed specific catalytic activity in organic transformations.

Engineering the direct metal coordination environment in single-atom catalysts, via adjustment of the oxide surface chemistry, is a powerful strategy towards reactivity modulation. An energetically facile depletion of surface oxygen on a Rh₁/SnO₂ catalyst unlocks an exceptional performance in the gas-phase hydroformylation of ethylene with syngas, hitherto exclusive of molecular catalysts operating in liquid environments.

Abstract

A frontier challenge in single-atom (SA) catalysis is the design of fully inorganic sites capable of emulating the high reaction selectivity traditionally exclusive of organometallic counterparts in homogeneous catalysis. Modulating the direct coordination environment in SA sites, via the exploitation of the oxide support's surface chemistry, stands as a powerful albeit underexplored strategy. We report that isolated Rh atoms stabilized on oxygen-defective SnO₂ uniquely unite excellent TOF with essentially full selectivity in the gas-phase hydroformylation of ethylene, inhibiting the thermodynamically favored olefin hydrogenation. Density Functional Theory calculations and surface characterization suggest that substantial depletion of the catalyst surface in lattice oxygen, energetically facile on SnO₂, is key to unlock a high coordination pliability at the mononuclear Rh centers, leading to an exceptional performance which is on par with that of molecular catalysts in liquid media.

Nature, Published online: 04 November 2022; doi:10.1038/d41586-022-03524-8

A Brazilian fossil suggests that the super-stretcher necks of Argentinosaurus and its ilk evolved gradually rather than in a rush.

Nature Synthesis, Published online: 27 October 2022; doi:10.1038/s44160-022-00180-8

Nucleophiles are versatile reagents that can engage in a plethora of C–C and C–heteroatom bond-forming reactions. This Review examines their increasing role in transition metal-catalysed directed C–H functionalization, with a focus on synthetic approaches involving organometallic nucleophiles and X-based (X = N, O and S) coupling partners.

Synthesis
DOI: 10.1055/a-1504-8366

Bimolecular nucleophilic substitution (SN2) is one of the most well-known fundamental reactions in organic chemistry to generate new molecules from two molecules. In principle, a nucleophile attacks from the back side of an alkylating agent having a suitable leaving group, most commonly a halide. However, alkyl halides are expensive, very harmful, toxic and not so stable, which makes them problematic for laboratory use. In contrast, trialkyl phosphates are inexpensive, readily accessible and stable at room temperature, under air, and are easy to handle, but rarely used as alkylating agents in organic synthesis. Here, we describe a mild, straightforward and powerful method for nucleophilic alkylation of various N-, O-, C- and S-nucleophiles using readily available trialkyl phosphates. The reaction proceeds smoothly in excellent yield, and quantitative yield in many cases, and covers a wide range of substrates. Further, the rare stereoselective transfer of secondary alkyl groups has been achieved with inversion of configuration of chiral centers (up to 98% ee).
[...]

Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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

Catalysts, Vol. 12, Pages 1304: Single-Atom Transition Metal Photocatalysts for Hydrogen Evolution Reactions

Catalysts doi: 10.3390/catal12111304

Authors: Thang Phan Nguyen Il Tae Kim

Hydrogen is one of the potential fuels that is easily stored in ammonia compounds and reacts with oxygen in an environmentally friendly manner, producing water and transferring a significant amount of heat for powering mechanical facilities or transportation. Recently, single-atom photocatalysts have attracted significant attention owing to their ability to produce clean fuels or reduce gaseous pollution, thereby contributing to the preservation of our planet. Utilizing metals composed of a single atom on a semiconductor platform can improve the active sites, thereby increasing the efficiency of the hydrogen evolution reaction. This review focuses on the use of single-atom transition metals as photocatalysts in a solar-powered water-splitting system that produces hydrogen gas. The approach to synthesis, reaction mechanism, and current performance of these materials is exhaustively discussed. In addition, the main challenges and improvement strategies are highlighted.