Backbone-controlled LUMO energy induces intramolecular C–H activation in ortho-bis-9-borafluorene-substituted phenyl and o-carboranyl compounds leading to novel 9,10-diboraanthracene derivatives

The choice of backbone linker for two ortho-bis-(9-borafluorene)s has a great influence on the LUMO located at the boron centers and, therefore, the reactivity of the respective compounds. Herein, we report the room temperature rearrangement of 1,2-bis-(9-borafluorenyl)-ortho-carborane, C₂B₁₀H₁₀-1,2-[B(C₁₂H₈)]₂ ([2a]) featuring o-carborane as the inorganic three-dimensional backbone and the synthesis of 1,2-bis-(9-borafluorenyl)benzene, C₆H₄-1,2-[B(C₁₂H₈)]₂ (2b), its phenylene analog. DFT calculations on the transition state for the rearrangement support an intramolecular C–H bond activation process via an S_EAr-like mechanism in [2a], and predicted that the same rearrangement would take place in 2b, but at elevated temperatures, which indeed proved to be the case. The rearrangement gives access to 3a and 3b as dibora-benzo[a]fluoroanthene isomers, a form of diboron polycyclic aromatic hydrocarbon (PAH) that had yet to be explored. The isolated compounds 2b, 3a, and 3b were fully characterized by NMR, HRMS, cyclic voltammetry (CV), single-crystal X-ray diffraction analysis, and photophysical measurements, supported by DFT and TD-DFT calculations.

The backbone linker for two ortho-bis-(9-borafluorene)s influences the LUMO at the boron centers and the reactivity of the respective compounds.     

Synthesis and Antiviral Properties against SARS-CoV-2 of Epoxybenzooxocino[4,3-b]Pyridine Derivatives

The COVID-19 pandemic is ongoing as of mid-2022 and requires the development of new therapeutic drugs, because the existing clinically approved drugs are limited. In this work, seven derivatives of epoxybenzooxocinopyridine were synthesized and tested for the ability to inhibit the replication of the SARS-CoV-2 virus in cell cultures. Among the described compounds, six were not able to suppress the SARS-CoV-2 virus’ replication. One compound, which is a derivative of epoxybenzooxocinopyridine with an attached side group of 3,4-dihydroquinoxalin-2-one, demonstrated antiviral activity comparable to that of one pharmaceutical drug. The described compound is a prospective lead substance, because the half-maximal effective concentration is 2.23 μg/μL, which is within a pharmacologically achievable range.     

High‐Pressure Synthesis of a Nitrogen‐Rich Inclusion Compound ReN8⋅x N2 with Conjugated Polymeric Nitrogen Chains

A nitrogen‐rich compound, ReN₈?x N₂, was synthesized by a direct reaction between rhenium and nitrogen at high pressure and high temperature in a laser‐heated diamond anvil cell. Single‐crystal X‐ray diffraction revealed that the crystal structure, which is based on the ReN₈ framework, has rectangular‐shaped channels that accommodate nitrogen molecules. Thus, despite a very high synthesis pressure, exceeding 100 GPa, ReN₈?x N₂ is an inclusion compound. The amount of trapped nitrogen (x) depends on the synthesis conditions. The polydiazenediyl chains [?N=N?]_∞ that constitute the framework have not been previously observed in any compound. Ab initio calculations on ReN₈?x N₂ provide strong support for the experimental results and conclusions.     

Partially Hydrogenated Graphene Materials Exhibit High Electrocatalytic Activities Related to Unintentional Doping with Metallic Impurities

Partially hydrogenated graphene materials, synthesized by the chemical reduction/hydrogenation of two different graphene oxides using zinc powder in acidic environment or aluminum powder in alkaline environment, exhibit high electrocatalytic activities, as well as electrochemical sensing properties. The starting graphene oxides and the resultant hydrogenated graphenes were characterized in detail. Their electrocatalytic activity was examined in the oxygen reduction reaction, whereas sensing properties towards explosives were tested by using picric acid as a redox probe. Findings indicate that the high electrocatalytic performance originates not only from the hydrogenation of graphene, but also from unintentional contamination of graphene with manganese and other metals during synthesis. A careful evaluation of the obtained data and a detailed chemical analysis are necessary to identify the origin of this anomalous electrocatalytic activity.     

Isolation of polymerase chain reaction-ready bacterial DNA from Lake Baikal sediments by carboxyl-functionalised magnetic polymer microspheres

Carboxyl group-containing magnetic nonporous poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) (P(HEMA-co-EDMA)) microspheres were used for the isolation of polymerase chain reaction (PCR)-ready DNA from samples of Baikal sediments. DNA was isolated using the phenol extraction method or the Soil DNA Isolation Kit. The occurrence of false-negative results in PCR caused by the presence of extracellular inhibitors in DNA samples was solved using solid phase reversible DNA immobilisation. PCR-ready DNA was reversibly adsorbed to the microspheres in the presence of 8.0% (w/v) poly(ethylene glycol) (PEG 6000) and 2.0M sodium chloride concentrations. The adsorbed DNA was released from the microspheres in a low ionic strength TE buffer. The quality of isolated DNA was checked by PCR amplification.     

The use of molecularly imprinted polymers for the multicomponent determination of endocrine‐disrupting compounds in water and sediment

The method employing molecularly imprinted polymers for the extraction and clean up of endocrine‐disrupting compounds (estrogens, bisphenol A, and alkylphenols) from water and sediment is described. The identical extraction/clean‐up and LC‐MS/MS condition were used for the analysis of both types of samples. The method showed high recoveries ranging from 90 to 99% with excellent precision (intrabatch: 3.6–9.3%; interbatch: 5.6–11.4% for water; intrabatch: 4.3–8.5%; interbatch: 6.1–9.6% for sediment). The LOD was in the range of 0.7–1.9 ng/L and 0.3–0.6 ng/g for water and sediment, respectively. Overall extraction on molecularly imprinted polymers substantially enhanced sample clean‐up. The difference in efficiency of clean‐up was particularly pronounced when a large sample volume/weight was extracted and analyzed. Finally, the method was successfully applied for the analysis of 20 water and sediment samples.     

The first tetranuclear vanadium(V) peroxo complex: Preparation, vibrational spectra and X-ray crystal structure of K6[V4O4(O2)8(PO4)]·9H2O

The vanadium(V) peroxo phosphato complex K₇[V₄O₄(O₂)₈(PO₄)]·9H₂O has been obtained from the KVO₃---KH₂PO₄---KOH---H₂O₂---H₂O---C₂H₅OH system. The X-ray structural analysis revealed a tetranuclear anionic structure in which two dinuclear [V₂O₂(O)₂)₂(μ-η¹ : η²-O₂)₂] units are connected by the μ₄-PO₄ group.     

Synthesis of 4-oxo-6-styryl-4H-pyran-2-carbonitriles and their application for the construction of new 4-pyrone derivatives

Research on Chemical Intermediates - Synthesis of 2-cyano-6-styryl-4-pyrones has been developed on the basis of 6-metylcomanic acid via modifications of the methyl and carboxyl groups. Reactions of...     

Asymmetric allylic alkylation of acyclic allylic ethers with organolithium reagents

A highly efficient, regio- and enantioselective Cu(I) /phosphoramidite-catalyzed asymmetric allylic alkylation of allyl ethers with organolithium reagents is reported. The use of organolithium reagents is essential for this catalytic C?C bond formation due to their compatibility with different Lewis acids. The versatility of allylic ethers under the copper-catalyzed reaction conditions with organolithium reagents is demonstrated in the shortest synthesis of (S)-Arundic acid.