560 research outputs found

    The Role of Nest Location on the Reproductive Success of Piping Plovers Breeding at Rockaway Beach, New York

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    The study’s goal was to learn what aspects of the piping plover experience affect reproductive outcomes at Rockaway Beach Endangered Species Nesting Area. Nest location was found to help predict reproductive success. Nests further from American oystercatcher nests were likely to fledge more chicks. Reproductive success was low in 2021

    Anthropogenic reaction parameters - the missing link between chemical intuition and the available chemical space

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    How do skilled synthetic chemists develop such a good intuitive expertise ? Why can we only access such a small amount of the available chemical space — both in terms of the re actions used and the chemical scaffolds we make? We argue here that these seemingly unrelated questions have a common root and are strongly interdependent . We performed a comprehensive analysis of organic reaction parameters dating back to 1771 and discove red that there are several anthropogenic factors that limit the reaction parameters and thus the scop e of synthetic chemistry. Nevertheless, many of the anthropogenic limitations such as the narrow parameter space and the opportunity of the rapid and clear feedback on the progress of reactions appear to be crucial for the acquisition of valid and reliable chemical intuition. In parallel, however, all of these same factors represent limitations for the exploration of available chemistry space and we argue th at these are thus at least partly responsible for limited access to new chemistries. We advocate, therefore, that the present anthropogenic boundaries can be expanded by a more conscious expl oration of “off - road” chemistry that would also extend the intuit ive knowledge of trained chemists

    Increasing Catalyst Efficiency in C−H Activation Catalysis

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    C−H activation reactions with high catalyst turnover numbers are still very rare in the literature and 10 mol % is a common catalyst loading in this field. We offer a representative overview of efficient C−H activation catalysis to highlight this neglected aspect of catalysis development and inspire future effort towards more efficient C−H activation. Examples ranging from palladium catalysis, Cp*Rh III - and Cp*Co III -catalysis, the C−H borylation and silylation to methane C−H activation are presented. In these reactions, up to tens of thousands of catalyst turnovers have been observed

    Photochemical C–H activation: generation of indole and carbazole libraries, and first total synthesis of clausenawalline D

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    The photolysis of N-aryltriazoles and N-arylbenzotriazoles leads to indoles and carbazoles, respectively. Because libraries of triazoles can be accessed rapidly, for example by the copper-catalyzed [3+2] cycloaddition reaction between alkynes and azides, this reaction allows the preparation of indoles in a single operation, by the simultaneous photolysis of the precursor library. As an example of such a synthesis of carbazoles, we prepared for the first time clausenawalline D, an antimalarial alkaloid that was recently isolated

    S,O-ligand-promoted palladium-catalyzed C-H olefination of arenes with allylic substrates

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    An efficient catalytic system for the C–H olefination of arenes with different allylic substrates is reported. The catalytic system is based on Pd(OAc)2 and a readily accessible bidentate S,O-ligand. The methodology shows high activity with a wide range of arenes, including bulky and, electron-rich and -poor arenes. The applicability of this catalyst is demonstrated in the late-stage functionalization of the complex molecule O-methylestrone

    Activation and Oxidation of Mesitylene C–H Bonds by (Phebox)Iridium(III) Complexes

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