Robby Vroemans

This work offers a simple methodolgy to avoid solvents and added catalysts for the synthesis of different kinds of N-substituted pyrrolidones. Different aniline derivatives with varying steric and electronic demands, aliphatic amines and benzyl amines were responsive to this methodology. The method was also modified for the synthesis of industrially important γ-valerolactone. Control experiments and DFT studies have also been carried out to find out the possible mechanistic pathway.

Abstract

An efficient, metal-free, catalyst-free and solvent-free methodology for the reductive amination of levulinic acid with different anilines has been developed using HBpin as the reducing reagent. This protocol offers an excellent method to avoid solvents and added catalysts on the synthesis of different kinds of N-substituted pyrrolidones under metal free conditions. It is also the first report for the synthesis of different pyrrolidones by solvent-free as well as catalyst-free methods. The proposed mechanism for the formation of pyrrolidone has been supported by DFT calculations and control experiments.

Nature, Published online: 17 May 2022; doi:10.1038/d41586-022-01372-0

In this review, an overview is given of chemical oxidants for the radical/electrophilic brominations starting from harmless bromide sources as an alternative for toxic molecular bromine. The characteristics of the active brominating species as well as plausible side reactions have been discussed.

Abstract

Bromination of organic substances is still an important reaction in modern synthetic chemistry. In view of the increasing demand for sustainable synthetic chemistry, oxidative bromination can play an important role to avoid the use of hazardous molecular bromine (Br₂). In this review, a complete overview of the chemical oxidants will be provided which have been used for the electrophilic as well as radical brominations, starting from less hazardous bromide Br(−I); e. g., HBr or a bromide salt, with a focus on the differences caused by the choice of oxidant.

Erich Hückel, R. Stephen Berry, and Edgar Heilbronner are three of the many theoretical and physical chemists who could have solved the pericyclic no-mechanism problem had R. B. Woodward posed the problem to them.

Abstract

It is a reasonable question to ask, why, as of 1965 when the five Woodward-Hoffmann communication appeared, did no other physical chemist or chemical physicist or theoretical chemist discover the orbital symmetry rules for all pericyclic reactions? Two theoretical chemists – Luitzen Oosterhoff (in 1961) and Kenichi Fukui (in 1964) had discovered portions of the orbital symmetry rules; their stories appear in the papers immediately preceding this paper which is Paper 5 in a 27-paper series on the history of Woodward-Hoffmann rules. Concise yet telling stories of 19 other chemists who could have, might have, perhaps even should have discovered the Woodward-Hoffmann rules are presented with explanations as to why they did not do so. Social, political, and scientific explanations will summarize the analyses.

Publication date: 12 May 2022

Source: Chem, Volume 8, Issue 5

Author(s): Bijin Li, Mazen Elsaid, Haibo Ge

Publication date: July 2022

Source: Trends in Chemistry, Volume 4, Issue 7

Author(s): Thomas Scattolin, Andreas Simoens, Christian V. Stevens, Steven P. Nolan

Nature, Published online: 12 May 2022; doi:10.1038/d41586-022-01278-x

Synthesis
DOI: 10.1055/a-1806-4513

The Ni-catalysed hydrogenolysis and cross-coupling of aryl ethers has emerged as a powerful synthetic tool to transform inert phenol-derived electrophiles into functionalised aromatic molecules. This has attracted significant interest due to its potential to convert the lignin fraction of biomass into chemical feedstocks, or to enable orthogonal reactivity and late-stage synthetic modification. Although the scope of nucleophiles employed, and hence the C–C and C–heteroatom bonds that can be forged, has expanded significantly since Wenkert’s seminal work in 1979, mechanistic understanding on how these reactions operate is still uncertain since the comparatively inert Caryl–O bond of aryl ethers challenge the involvement of classical mechanisms involving direct oxidative addition to Ni(0). In this review, we document the different mechanisms that have been proposed in the Ni-catalysed hydrogenolysis and cross-coupling of aryl ethers. These include: (i) direct oxidative addition; (ii) Lewis acid assisted C–O bond cleavage; (iii) anionic nickelates, and; (iv) Ni(I) intermediates. Experimental and theoretical investigations by numerous research groups have generated a pool of knowledge that will undoubtedly facilitate future discoveries in the development of novel Ni-catalysed transformations of aryl ethers.1 Introduction2 Direct Oxidative Addition3 Hydrogenolysis of Aryl Ethers4 Lewis Acid Assisted C–O Bond Cleavage5 Anionic Nickelates6 Ni(I) Intermediates7 The ‘Naphthalene Problem’8 Conclusions and Outlook
[...]

Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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

Nature Reviews Chemistry, Published online: 12 May 2022; doi:10.1038/s41570-022-00395-5

Metal/metal dual catalysis involving the activation of inert C−H bond offers unique opportunities in organic synthesis. This micro-review summarizes the most recent advances in this rapidly developing area with an emphasis on mechanism discussion, collecting examples according to the role of the metal species.

Abstract

Metal/metal dual catalysis provides new viewpoints and opportunities for C−H functionalization, especially in reactivity and selectivity control aspects. It helps to realize sequential or cooperative catalytic transformations in one-pot, shortening the synthetic steps in target molecules construction. This micro-review summarizes the most recent advances in this research field, discusses related mechanism, collecting examples according to the role of the metal species.

Nature Communications, Published online: 11 May 2022; doi:10.1038/s41467-022-30256-0

Synthesis
DOI: 10.1055/a-1811-8503

1,1-Difunctionalization of α‑carbonyl sulfur ylides and thiosulfonates under simple conditions is disclosed. In this protocol, two new C–S bonds are constructed in a one-step reaction. A series of aliphatic and aromatic β-keto thiosulfones were obtained in moderate to good yields. This reaction probably proceeds through sulfur ylide-involved­ nucleophilic substitution of an ion pair within a solvent cage.
[...]

Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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

A reactive-group guided approach is taken to synthesize atomically dispersed Ni catalysts on red phosphorus. The advanced system consists of Janus single-atom Ni sites: P−Ni for water reduction and P−O−Ni for water oxidation, leading to the efficient separation of electron-hole pairs and overall improved photocatalytic water splitting activity.

Abstract

Single-atom nickel catalysts hold great promise for photocatalytic water splitting due to their plentiful active sites and cost-effectiveness. Herein, we adopt a reactive-group guided strategy to prepare atomically dispersed nickel catalysts on red phosphorus. The hydrothermal treatment of red phosphorus leads to the formation of P−H and P−OH groups, which behave as the reactive functionalities to generate the dual structure of single-atom P−Ni and P−O−Ni catalytic sites. The produced single-atom sites provide two different functions: P−Ni for water reduction and P−O−Ni for water oxidation. Benefitting from this specific Janus structure, Ni-red phosphorus shows an elevated hydrogen evolution rate compared to Ni nanoparticle-modified red phosphorus under visible-light irradiation. The hydrogen evolution rate was additionally enhanced with increased reaction temperature, reaching 91.51 μmol h⁻¹ at 70 °C, corresponding to an apparent quantum efficiency of 8.9 % at 420 nm excitation wavelength.

PdFe₁ single-atom alloy metallene is demonstrated as an effective and robust catalyst for the nitrogen reduction reaction (NRR), delivering an NH₃ yield of 111.9 μg h⁻¹ mg⁻¹ and a Faradaic efficiency of 37.8 % at −0.2 V (RHE). Combined theoretical computations and operando XAS/Raman spectroscopy identify Pd-coordinated Fe single atoms as active centers to enable efficient N₂ activation, reduced protonation energy barriers, suppressed hydrogen evolution and high electrocatalytic stability.

Abstract

Single-atom alloys hold great promise for electrocatalytic nitrogen reduction reaction (NRR), while the comprehensive experimental/theoretical investigations of SAAs for the NRR are still missing. Herein, PdFe₁ single-atom alloy metallene, in which the Fe single atoms are confined on a Pd metallene support, is first developed as an effective and robust NRR electrocatalyst, delivering exceptional NRR performance with an NH₃ yield of 111.9 μg h⁻¹ mg⁻¹, a Faradaic efficiency of 37.8 % at −0.2 V (RHE), as well as a long-term stability for 100 h electrolysis. In-depth mechanistic investigations by theoretical computations and operando X-ray absorption/Raman spectroscopy indentify Pd-coordinated Fe single atoms as active centers to enable efficient N₂ activation via N₂-to-Fe σ-donation, reduced protonation energy barriers, suppressed hydrogen evolution and excellent thermodynamic stability, thus accounting for the high activity, selectivity and stability of PdFe₁ for the NRR.

The Cover Feature shows propane dehydrogenation on an Ru single atom anchored at the N vacancy on the hexagonal BN (h-BN) sheet. In their Research Article, C. Xiong et al. investigate the stability of Pt, Au, and Ru single atoms anchored at B and N vacancies on h-BN and their potential for propane dehydrogenation using first principles density function theory and molecular dynamics. They find that Pt single atom at the B vacancy in h-BN and Ru single atom at the N vacancy in h-BN are very stable and show excellent activity for propane dehydrogenation, as evidenced by low energy barriers for both dehydrogenation steps. Their work suggests that Pt and Ru single atoms anchored at vacancy sites in h-BN could be promising catalysts for propane dehydrogenation. More information can be found in the Research Article by C. Xiong et al.

Nature Chemistry, Published online: 05 May 2022; doi:10.1038/s41557-022-00939-8