Robby Vroemans

The amorphization of the support for single-atoms catalysts (SACs) is another efficient but unknown strategy in improving the catalytic properties through adjusting the electronic metal–support interaction (MSI). This work showcases a model ruthenium SAC and expounds on how the flexibly amorphous configuration of the support matrix functions unexpectedly in intensifying the MSI and further accelerating hydrogen evolution reaction (HER) kinetics of SACs.

Abstract

Amorphization of the support in single-atom catalysts is a less researched concept for promoting catalytic kinetics through modulating the metal–support interaction (MSI). We modeled single-atom ruthenium (Ru_SAs) supported on amorphous cobalt/nickel (oxy)hydroxide (Ru-a-CoNi) to explore the favorable MSI between Ru_SAs and the amorphous skeleton for the alkaline hydrogen evolution reaction (HER). Differing from the usual crystal counterpart (Ru-c-CoNi), the electrons on Ru_SAs are facilitated to exchange among local configurations (Ru-O-Co/Ni) of Ru-a-CoNi since the flexibly amorphous configuration induces the possible d–d electron transfer and medium-to-long range p–π orbital coupling, further intensifying the MSI. This embodies Ru-a-CoNi with enhanced water dissociation, alleviated oxophilicity, and rapid hydrogen migration, which results in superior durability and HER activity of Ru-a-CoNi, wherein only 15 mV can deliver 10 mA cm⁻², significantly lower than the 58 mV required by Ru-c-CoNi.

Publication date: 29 January–12 February 2022

Source: Tetrahedron, Volumes 106–107

Author(s): Adam Włodarczyk

This review summarizes the reaction development of nitriles, including hydration, hydrolysis and reduction reactions both in homogeneous and heterogeneous systems. The characteristics of different catalytic systems are introduced in detail.

Abstract

Nitrile represents a synthetically important class of compounds, relevant to the preparation of fine organic chemicals, natural products, and biologically active molecules. The electronegative nitrogen atom and electropositive carbon atom of cyano group endow nitriles with rich and diverse chemical properties. Traditional chemical transformations of nitriles usually involve the use of strong acids, bases, and other harsh conditions. To overcome these limitations, various catalytic methods have been explored both in homogeneous and heterogeneous systems. In this review, we summarize some of the recent progress on the development of efficient synthetic methods involving nitriles. Especially, the classic transformations of nitriles including hydration, hydrolysis and reduction reactions are discussed in detail, which provide rapid access to a series of important small molecules, such as amides, ketones, amines, and imines. The reaction development, as well as the design of the catalytic system will be discussed with special emphasis placed on the mechanistic aspects.

This review portrays rearrangements with substrates of various genres in Scholl reaction. The rearranged products formed due to automerization, migration of substituents, rearrangement accompanied by cyclization, ring expansion, and ring contraction under Scholl-type reactions are gathered. In cases where new ring is constructed, they are grouped based on ring size. The crucial factors that drive rearrangements via enigmatic intermediates and the methods for successful prevention of rearrangements are also discussed.

Abstract

Rearrangements in Scholl reaction are mostly serendipitous. The design of molecular precursors is what seems to guide the course of rearrangement. This review consolidates different classes of precursors used in Scholl reaction and their accompanying rearrangements that include aryl migration, migration followed by cyclization and skeletal rearrangements involving ring expansion, ring contraction and both, under the reaction conditions. The attempt in collating heretofore-reported examples in this review is to guide designing appropriate precursors to predictably achieve complex molecular structures or nanographenes or defect-nanographenes via rearrangement.

In the presence of a catalytic quantity of a nitroxide salt, sodium persulfate can be used for the oxidative amidation of aldehydes to yield acyl azoles.

Abstract

A methodology for the oxidative amidation of aldehydes to yield N-acyl azoles is reported. The approach employs sodium persulfate and a catalytic amount of a nitroxide and is applicable to a range of structurally diverse substrates.

Abstract

A Pd(II)-catalyzed atropselective olefination of biaryls with maleimides is reported using chiral transient directing group (CTDG) strategy L-tert-leucine is used as a chiral auxiliary to obtain atropselective biaryl aldehydes with enantiomeric excess ranging from 70 to 99%. The method is also applicable for other olefins such as acrylonitrile, phenyl vinyl sulfone, and N-tert-butyl acrylamide, providing corresponding atropselective biaryl aldehydes with 97–99% ee. Non-linear effect studies suggest that chiral auxiliary is responsible for the atropselectivity of products. Other studies suggested the critical role of reaction time on yield and s-factor of desired products.

Publication date: 15 March 2022

Source: Coordination Chemistry Reviews, Volume 455

Author(s): Shao-Fei Ni, Guanglong Huang, Yonghui Chen, James S. Wright, Mingde Li, Li Dang

Abstract

The preparation of various 5- and 6-azaindoles, heterocyclic structures that are frequently part of molecules in clinical development, and their monohydroxy analogues were described. Different strategies, relying on the de novo pyrrole ring formation, were investigated and, thanks to Hemetsberger–Knittel, Bartoli and Leimgruber–Batcho approaches, 4- and 7-monohydroxy 5- and 6-azaindoles were obtained. The crucial introduction of the oxygen atom was carried out from halogen derivatives, using nucleophilic substitution reactions under basic conditions with or without a copper catalyst. Some preliminary oxidation reactions have shown that it was yet not possible to synthesize the azaquinone indole structure from monohydroxy azaindole, using molecular oxygen in the presence of salcomine as a catalyst.

Mask recycling: Surgical masks are subjected to pyrolysis processes at controlled temperature and atmosphere in order to transform them into valuable products. Crude oil is formed during pyrolysis and analyzed. The char produced from the process is functionalized with metal-phthalocyanine and then tested as the electrocatalyst for oxygen reduction reaction and hydrogen evolution reaction in neutral and alkaline media.

Abstract

A novel route for the valorization of waste into valuable products was developed. Surgical masks commonly used for COVID 19 protection by stopping aerosol and droplets have been widely used, and their disposal is critical and often not properly pursued. This work intended to transform surgical masks into platinum group metal-free electrocatalysts for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) as well as into crude oil. Surgical masks were subjected to controlled-temperature and -atmosphere pyrolysis, and the produced char was then converted into electrocatalysts by functionalizing it with metal phthalocyanine of interest. The electrocatalytic performance characterization towards ORR and HER was carried out highlighting promising activity. At different temperatures, condensable oil fractions were acquired and thoroughly analyzed. Transformation of waste surgical masks into electrocatalysts and crude oil can open new routes for the conversion of waste into valuable products within the core of the circular economy.