Electron-transfer catalyzed cycloaddition reactions of unactivated cyclic olefins in weakly coordinating anion electrolyte

Cis-Cyclooctene, C8H14, undergoes an efficient electron-transfer (ET) catalyzed cycloaddition reaction in dichloromethane containing NBu4B(C6F5)4 as supporting electrolyte. The reactions were initiated by in-situ anodic generation of catalytic amounts of either N(2,4-C6H3Br2)3+ (1+, "magic green") or ReCp(CO)3+ (2+, Cp = ($\eta$5-C5H5)). The olefin radical chain reaction induced by ET mediation was complete in less than 10 min, some 100-1000 times faster than the optimum photochemically induced preparations of cyclobutane derivatives from cyclic olefins. Yields of up to 87{\%} of mixtures of C16H28 isomers were obtained at an electro-synthetic level. Use of the weakly coordinating B(C6F5)4- anion, rather than a traditional small anion such as PF6- or ClO4-, was required to carry out the cyclization reactions. The more easily oxidized trans-cyclooctene, when anodized directly at an electrode, gave a similar isomeric mixture of cyclobutanes. Cycloheptene and cyclohexene underwent similar 2 + 2 coupling to give cyclobutane products. Cyclopentene gave a 2 + 2 + 2 cyclized trimer. The mechanism appears to involve a key radical-substrate propagation step in which an olefin radical cation reacts with a neutral olefin to give a cyclobutyl radical cation, which then accepts an electron, most likely from another olefin, to form the final neutral compound. Although the E1/2 potentials of the ET mediators are 660-900 mV lower than the estimated oxidation potentials of the olefins, the endergonic nature of the ET initiation step works to the advantage of the chain process by favoring the radical-substrate propagation step

Evidence for a p dimer in the electrochemical reduction of 1,3,5-trinitrobenzene : a reversible N2-fixation system

Premi a l'excel·lència investigadora. Àmbit de les Ciències Experimentals. 200

3D-hybrid networks with controllable electrical conductivity from the electrochemical deposition of terthiophene-functionalized polyphenylene dendrimers

(Figure Presented) Unusual conductivity effects: Suitably functionalized dendrimers (see picture) are capable of forming truly covalent three-dimensional networks with remarkably high conductivity on electrochemical doping. Depending on the charging level of the electroactive components used as building blocks for the dendrimer core and the perimeter, two separated regimes of electrical conductivity can be observed

Evaluating the food safety and risk assessment evidence-base of polyethylene terephthalate oligomers: Protocol for a systematic evidence map

Polyethylene terephthalate (PET) oligomers are ubiquitous in PET used in food contact applications. Consumer exposure by migration of PET oligomers into food and beverages is documented. However, no specific risk assessment framework or guidance for the safety evaluating of PET oligomers exist to date.; The aim of this systematic evidence map (SEM) is to identify and organize existing knowledge clusters and associated gaps in hazard and exposure information of PET oligomers. Research needs will be identified as an input for chemical risk assessment, and to support future toxicity testing strategies of PET oligomers and regulatory decision-making.; Multiple bibliographic databases (incl. Embase, Medline, Scopus, and Web of Science Core Collection), chemistry databases (SciFinder-n, Reaxys), and gray literature sources will be searched, and the search results will be supplemented by backward and forward citation tracking on eligible records. The search will be based on a single-concept PET oligomer-focused strategy to ensure sensitive and unbiased coverage of all evidence related to hazard and exposure in a data-poor environment. A scoping exercise conducted during planning identified 34 relevant PET oligomers. Eligible work of any study type must include primary research data on at least one relevant PET oligomer with regard to exposure, health, or toxicological outcomes.; For indexed scientific literature, title and abstract screening will be performed by one reviewer. Selected studies will be screened in full-text by two independent reviewers. Gray literature will be screened by two independent reviewers for inclusion and exclusion.; Risk of bias analysis will not be conducted as part of this SEM.; Will be performed by one reviewer and peer-checked by a second reviewer for indexed scientific literature or by two independent reviewers for gray literature.; The extracted and coded information will be synthesized in different formats, including narrative synthesis, tables, and heat maps.; Zenodo: https://doi.org/10.5281/zenodo.6224302

Einsatz von Bakteriorhodopsin in Mikroelektronik-Technologien (BAROMIK). Teilvorhaben 1: Erprobung und Bewertung von Bakteriorhodopsin zur Erzeugung von Metallstrukturen fuer die Mikroelektronik. Teilvorhaben 2: Bereitstellung und Modifikation von Bakteriorhodopsin zur Verwendung in Metallisierungsverfahren. Teilvorhaben 3: Biomimetische Technologie zur Erzeugung strukturierter Metallfilme Gemeinsamer Schlussbericht

Available from TIB Hannover: F99B41+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman