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      Electrochemical Minisci-type trifluoromethylation of electron-deficient heterocycles mediated by bromide ions

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          Abstract

          An electrochemical methodology for the Minisci-type trifluoromethylation of electron-deficient heterocycles mediated by cheap and easily available bromide ions has been developed.

          Abstract

          An electrochemical methodology for the Minisci-type trifluoromethylation of electron-deficient heterocycles mediated by cheap and easily available bromide ions has been developed. By virtue of the in situ generated sulfonyl hypobromite intermediate, the CF 3 radical can be regulated and controlled at a low concentration, thereby improving the reaction efficiency over direct electrolysis. Also, this indirect electrochemical process is performed in a beaker-type undivided cell under galvanostatic conditions, without using external expensive supporting electrolytes. This protocol provides an alternative electrochemical trifluoromethylation methodology for the late-stage functionalization of biologically important molecules.

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          Is Open Access

          Structural absorption by barbule microstructures of super black bird of paradise feathers

          Many studies have shown how pigments and internal nanostructures generate color in nature. External surface structures can also influence appearance, such as by causing multiple scattering of light (structural absorption) to produce a velvety, super black appearance. Here we show that feathers from five species of birds of paradise (Aves: Paradisaeidae) structurally absorb incident light to produce extremely low-reflectance, super black plumages. Directional reflectance of these feathers (0.05–0.31%) approaches that of man-made ultra-absorbent materials. SEM, nano-CT, and ray-tracing simulations show that super black feathers have titled arrays of highly modified barbules, which cause more multiple scattering, resulting in more structural absorption, than normal black feathers. Super black feathers have an extreme directional reflectance bias and appear darkest when viewed from the distal direction. We hypothesize that structurally absorbing, super black plumage evolved through sensory bias to enhance the perceived brilliance of adjacent color patches during courtship display.
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            Trifluoromethylation of arenes and heteroarenes by means of photoredox catalysis.

            Modern drug discovery relies on the continual development of synthetic methodology to address the many challenges associated with the design of new pharmaceutical agents. One such challenge arises from the enzymatic metabolism of drugs in vivo by cytochrome P450 oxidases, which use single-electron oxidative mechanisms to rapidly modify small molecules to facilitate their excretion. A commonly used synthetic strategy to protect against in vivo metabolism involves the incorporation of electron-withdrawing functionality, such as the trifluoromethyl (CF(3)) group, into drug candidates. The CF(3) group enjoys a privileged role in the realm of medicinal chemistry because its incorporation into small molecules often enhances efficacy by promoting electrostatic interactions with targets, improving cellular membrane permeability, and increasing robustness towards oxidative metabolism of the drug. Although common pharmacophores often bear CF(3) motifs in an aromatic system, access to such analogues typically requires the incorporation of the CF(3) group, or a surrogate moiety, at the start of a multi-step synthetic sequence. Here we report a mild, operationally simple strategy for the direct trifluoromethylation of unactivated arenes and heteroarenes through a radical-mediated mechanism using commercial photocatalysts and a household light bulb. We demonstrate the broad utility of this transformation through addition of CF(3) to a number of heteroaromatic and aromatic systems. The benefit to medicinal chemistry and applicability to late-stage drug development is also shown through examples of the direct trifluoromethylation of widely prescribed pharmaceutical agents.
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              Enantioselective alpha-trifluoromethylation of aldehydes via photoredox organocatalysis.

              The first enantioselective, organocatalytic alpha-trifluoromethylation and alpha-perfluoroalkylation of aldehydes have been accomplished using a readily available iridium photocatalyst and a chiral imidazolidinone catalyst. A range of alpha-trifluoromethyl and alpha-perfluoroalkyl aldehydes were obtained from commercially available perfluoroalkyl halides with high efficiency and enantioselectivity. The resulting alpha-trifluoromethyl aldehydes were subsequently shown to be versatile precursors for the construction of a variety of enantioenriched trifluoromethylated building blocks.
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                Author and article information

                Contributors
                (View ORCID Profile)
                Journal
                OCFRA8
                Organic Chemistry Frontiers
                Org. Chem. Front.
                Royal Society of Chemistry (RSC)
                2052-4129
                July 9 2019
                2019
                : 6
                : 14
                : 2392-2397
                Affiliations
                [1 ]Beijing Key Laboratory of Environmental and Viral Oncology
                [2 ]College of Life Science & Bioengineering
                [3 ]Beijing University of Technology
                [4 ]Beijing 100124
                [5 ]China
                Article
                10.1039/C9QO00552H
                4b94fd4c-ef64-4ff9-8a62-0f0c20857bbe
                © 2019

                http://rsc.li/journals-terms-of-use

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