Solid Acid Catalysts for the Hock Cleavage of Hydroperoxides

The oxidation of cumene and following cleavage of cumene hydroperoxide (CHP) with sulfuric acid (Hock rearrangement) is still, by far, the dominant synthetic route to produce phenol. In 2020, the global phenol market reached a value of 23.3 billion US$ with a projected compound annual growth rate of 3.4% for 2020–2025. From ecological and economical viewpoints, the key step of this process is the cleavage of CHP. One sought-after way to likewise reduce energy consumption and waste production of the process is to substitute sulfuric acid with heterogeneous catalysts. Different types of zeolites, silicon-based clays, heteropoly acids, and ion exchange resins have been investigated and tested in various studies. For every type of these solid acid catalysts, several materials were found that show high yield and selectivity to phenol. In this mini-review, first a brief introduction and overview on the Hock process is given. Next, the mechanism, kinetics, and safety aspects are summarized and discussed. Following, the different types of heterogeneous catalysts and their performance as catalyst in the Hock process are illustrated. Finally, the different approaches to substitute sulfuric acid in the synthetic route to produce phenol are briefly concluded and a short outlook is given.

Simplified Synthesis and Stability Assessment of Aflatoxin B1-Lysine and Aflatoxin G1-Lysine

Aflatoxins B1 (AFB1) and G1 (AFG1) are carcinogenic mycotoxins that contaminate crops such as maize and groundnuts worldwide. The broadly accepted method to assess chronic human aflatoxin exposure is by quantifying the amount of aflatoxin adducted to human serum albumin. This has been reported using ELISA, HPLC, or LC-MS/MS to measure the amount of AFB1-lysine released after proteolysis of serum albumin. LC-MS/MS is the most accurate method but requires both isotopically labelled and unlabelled AFB1-lysine standards, which are not commercially available. In this work, we report a simplified synthetic route to produce unlabelled, deuterated and 13C6 15N2 labelled aflatoxin B1-lysine and for the first-time aflatoxin G1-lysine. Additionally, we report on the stability of these compounds during storage. This simplified synthetic approach will make the production of these important standards more feasible for laboratories performing aflatoxin exposure studies.

The Rearrangement of Alkylallenes to 1,3-Dienes

1,3-Dienes are vital building blocks in organic synthesis. They underpin many fundamental synthetic transformations and are present in numerous natural products and drug candidate molecules. The rearrangement of an alkylallene to a 1,3-diene is an atom efficient, redox neutral, transformation that provides a straightforward synthetic route to functionalized 1,3-dienes. Herein, we provide an account of this transformation using allenes that are not predisposed by the presence of heteroatoms or electron-withdrawing groups directly attached to the allene. Early reports of this skeletal rearrangement are acid-mediated approaches, with limited substrate scope, but they provide valuable mechanistic insights. More recent transition metal-mediated approaches that exhibit improved substrate scope are described, together with isolated examples that have utilized this rearrangement.

SARS-CoV-2 Is a Robot Bioweapon

Two possibilities should be considered for the origin of SARS-CoV-2: natural evolution or laboratory creation. In the authors' earlier report titled “Unusual Features of the SARS-CoV-2 Genome Suggesting Sophisticated Laboratory Modification Rather Than Natural Evolution and Delineation of Its Probable Synthetic Route,” they disproved the possibility of SARS-CoV-2 arising naturally through evolution and instead proved that SARS-CoV-2 must have been a product of laboratory modification. Despite this and similar efforts, the laboratory creation theory continues to be downplayed or even diminished. This is fundamentally because the natural origin theory remains supported by several novel coronaviruses published after the start of the outbreak. Here, however, the authors use in-depth analyses of the available data and literature to prove that these novel animal coronaviruses do not exist in nature.

Synergistically Enhanced Iron and Zinc Bimetallic Sites as an Advanced ORR Electrocatalyst for Flow Liquid Rechargeable Zn-air Batteries

N-coordinated transition-metal materials are promising electrocatalysts for various sustainable and efficient electrochemical energy conversion and storage devices. Here we reported a simple synthetic route of simultaneously crafting Fe and Zn...

A novel domino protocol for three-component synthesis of new dibenzo[e,g]indoles: flexible intramolecular charge transfers

Fairly high yields of 2-aryl-3-nitrodibenzo[e,g]¬¬¬¬indoles were synthesized via a hitherto unreported domino-reaction of 9,10-phenanthrenequinone, ammonium acetate and β-nitrostyrenes in one pot. This novel three-component synthetic route is efficaciously catalysed by...

An iron-catalyzed domino reaction of donor–acceptor cyclopropanes: a diastereoselective approach towards diversely functionalized pyrrolo-quinazolines

An expeditious synthetic route to access functionalized pyrrolo[2,1-b]quinazoline scaffolds has been achieved via domino ring opening cyclization (DROC) reactions of donor–acceptor (D–A) cyclopropanes and 2-amino(methyl)aniline derivatives.