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Electron-rich aryl acetates derived from (renewable) phenolics were selectively reduced to the corresponding arenes using pinacolborane (HBpin) and a nickel-N-heterocyclic carbene (NHC) catalytic system in the green solvent dimethylcarbonate (DMC). The method is applicable to 4-propylguaiacyl acetate derived from pine wood.

Abstract

Acetate serves as a renewable and easily installed leaving group for selective deoxygenation of phenolics (ArOH). Ni-catalyzed hydrodeacetoxylation of aryl acetates (Ar−OAc) with HBpin in a green carbonate solvent selectively delivers the corresponding deoxygenated arenes (ArH). The method is also applicable to highly challenging guaiacyl and syringyl acetates, leaving −OMe groups intact without arene reduction. Renewable 4-propylguaiacol obtained from pine can also be transformed without significant loss in yield versus oil derived feedstock. The observed chemoselectivity for Ar−OAc versus ArO−Ac bond cleavage was rationalized based on mechanistic experiments and DFT calculations. ArOH side-product formation is attributed to direct competitive Ni-catalyzed reduction of the C=O bond. Hydrodeacyloxylation of a set of aryl alkanoates featured interesting chemoselectivity with a dramatic influence of the length and structure of the alkyl chain on catalysis.

Nature Reviews Chemistry, Published online: 21 March 2022; doi:10.1038/s41570-022-00372-y

Publication date: 9 April 2022

Source: Tetrahedron, Volume 111

Author(s): V.R. Padma Priya, K. Natarajan, Ganesh Chandra Nandi

This paper focuses on key aspects of academic research culture that can impact STEM researcher mental health: bullying and harassment; precarity of contracts; diversity, inclusion, and accessibility; and the competitive research landscape, as well as exploring why mental health matters for researchers. Further, key recommendations are provided and actionable steps are outlined that institutions can take to make research in STEM inclusive for all.

Abstract

The onset of COVID-19, coupled with the finer lens placed on systemic racial disparities within our society, has resulted in increased discussions around mental health. Despite this, mental health struggles in research are still often viewed as individual weaknesses and not the result of a larger dysfunctional research culture. Mental health interventions in the science, technology, engineering, and mathematics (STEM) academic community often focus on what individuals can do to improve their mental health instead of focusing on improving the research environment. In this paper, we present four aspects of research that may heavily impact mental health based on our experiences as research scientists: bullying and harassment; precarity of contracts; diversity, inclusion, and accessibility; and the competitive research landscape. Based on these aspects, we propose systemic changes that institutions must adopt to ensure their research culture is supportive and allows everyone to thrive.

Bono VOCs: Volatile organic compounds (VOCs) are detrimental to the environment and human health and must be eliminated. Precious metal catalysts are highly active for oxidation of VOCs, but their rarity and high price limits large-scale application. Supported metal single-atom catalysts (SACs) have high atom efficiency and can mitigate such limitations. This Review summarizes recent advances in the use of SACs for oxidation of VOCs.

Abstract

Volatile organic compounds (VOCs) are detrimental to the environment and human health and must be eliminated before discharging. Oxidation by heterogeneous catalysts is one of the most promising approaches for the VOCs abatement. Precious metal catalysts are highly active for the catalytic oxidation of VOCs, but they are rare and their high price limits large-scale application. Supported metal single-atom catalysts (SACs) have a high atom efficiency and provide the possibility to circumvent such limitations. This Review summarizes recent advances in the use of metal SACs for the complete oxidation of VOCs, such as benzene, toluene, formaldehyde, and methanol, as well as aliphatic and Cl- and S-containing hydrocarbons. The structures of the metal SACs used and the reaction mechanisms of the VOC oxidation are discussed. The most widely used SACs are noble metals supported on oxides, especially on reducible oxides, such as Mn₂O₃ and TiO₂. The reactivity of most SACs is related to the activity of surface lattice oxygen of the oxides. Furthermore, several metal SACs show better reactivity and improved S and Cl resistance than the corresponding nanocatalysts, indicating that SACs have potential for application in the oxidation of VOCs. The deactivation and regeneration mechanisms of the metal SACs are also summarized. It is concluded that the application of metal SACs in catalytic oxidation of VOCs is still in its infancy. This Review aims to elucidate structure–performance relationships and to guide the design of highly efficient metal SACs for the catalytic oxidation of VOCs.

The big reveal: Hydrodehalogenation of 35 different aryl halides (Ar−I, Ar−Br, and Ar−Cl) is performed using a heterogeneous nickel catalyst (Ni-phen@TiO₂-800) and molecular hydrogen. This work represents an effective strategy for converting thermally and chemically inert hazardous compounds into their less noxious congeners. Characterization of the catalyst reveals nickel nanoparticles covered with N-doped carbon layers.

Abstract

Hydrodehalogenation is an effective strategy for transforming persistent and potentially toxic organohalides into their more benign congeners. Common methods utilize Pd/C or Raney-nickel as catalysts, which are either expensive or have safety concerns. In this study, a nickel-based catalyst supported on titania (Ni-phen@TiO₂-800) is used as a safe alternative to pyrophoric Raney-nickel. The catalyst is prepared in a straightforward fashion by deposition of nickel(II)/1,10-phenanthroline on titania, followed by pyrolysis. The catalytic material, which was characterized by SEM, TEM, XRD, and XPS, consists of nickel nanoparticles covered with N-doped carbon layers. By using design of experiments (DoE), this nanostructured catalyst is found to be proficient for the facile and selective hydrodehalogenation of a diverse range of substrates bearing C−I, C−Br, or C−Cl bonds (>30 examples). The practicality of this catalyst system is demonstrated by the dehalogenation of environmentally hazardous and polyhalogenated substrates atrazine, tetrabromobisphenol A, tetrachlorobenzene, and a polybrominated diphenyl ether (PBDE).