930 research outputs found
Catalytic Access to Diastereometrically Pure Four‐ and Five‐Membered Silyl‐Heterocycles Using Transborylation
Get PDF: Silyl-heterocycles offer a unique handle to expand and explore chemical space, reactivity, and functionality. The shortage of catalytic methods for the preparation of diverse and functionalized silyl-heterocycles however limits widespread exploration and exploitation. Herein the borane-catalyzed intramolecular 1,1-carboboration of silyl-alkynes has been developed for the synthesis of 2,3-dihydrosilolyl and silylcyclobut-2-enyl boronic esters. Successful, catalytic carboboration has been achieved on a variety of functionally diverse silyl-alkynes, using a borane catalyst and transborylation-enabled turnover. Mechanistic studies, including 13C-labelling, computational studies, and single-turnover experiments, suggest a reaction pathway proceeding by 1,2-hydroboration, 1,1-carboboration, and transborylation to release the alkenyl boronic ester product and regenerate the borane catalyst
From Foucauldian Biopower to Energopower and Infopower:An Interview with Dominic Boyer and Colin Koopman
No full textKirsten Hasberg talks to Dominic Boyer, anthropologist and author of Energopolitics: Wind and Power in the Anthroprocene, and to Colin Koopman, philosopher and author of How We Became our Data: A Genealogy of the Informational Person. Their books published in mid-2019 put forward novel conceptualizations of Foucauldian biopower, which they term infopower and energopower, respectively. Criss-crossing between philosophical conceptualizations and concrete problems like the struggles of renewable energy communities (Boyer) and the influence of economic thinking on datafication (Koopman), the conversations show how Foucauldian concepts are relevant to today's power struggles inherent to the energy transition and the digital transformation.Kirsten Hasberg talks to Dominic Boyer, anthropologist and author of Energopolitics: Wind and Power in the Anthroprocene, and to Colin Koopman, philosopher and author of How We Became our Data: A Genealogy of the Informational Person. Their books published in mid-2019 put forward novel conceptualizations of Foucauldian biopower, which they term infopower and energopower, respectively. Criss-crossing between philosophical conceptualizations and concrete problems like the struggles of renewable energy communities (Boyer) and the influence of economic thinking on datafication (Koopman), the conversations show how Foucauldian concepts are relevant to today's power struggles inherent to the energy transition and the digital transformation
Simple guide to urban land regularization in the informal settlements in Kenya
No full textAuthor: Dominic Mutuk
Mary\u27s Knowledge of Her Son\u27s Divinity at the Annunciation: The Papal Tradition
Get PDFAbout the author: Rev. Dominic Unger, O.F.M. Cap., has written widely on Marian scholarship and various scriptural questions
Global history and critiques of western perspectives
No full textThe article discusses the parameters of the expanding field of global history and its wider methodological implications. In a first step the author outlines the rising interest in transcultural and global history that can be observed in many parts of the world. In this context different approaches to global history as well as alternative methodologies and periodizations are discussed. In a second step the author reflects upon the possibilities and challenges for global history in an age in which universalism and Eurocentrism have long come under attack from many different directions. The article discusses dependency theory and subaltern studies as two very different precursors to the current critiques of Eurocentrism. The impact and legacy of such schools, the author argues, cannot be ignored by global historians, even though they do not need to get directly involved in these academic discourses. The piece ends with scenarios for multipolar and pluralistic perspectives on the past
Intermolecular Sp<sup>3</sup>C─H Metalation of Non‐Nucleophilic Brønsted Bases Using Simple Lewis Acids
No full text2,6‐Di‐tert‐butyl substituted pyridines (tBu2‐py) are widely used non‐nucleophilic Brønsted bases. Their ubiquity is due to their highly hindered basic site and chemically robust nature. Herein we report that simple M2X6 Lewis acids (M═Al or Ga, X═Cl, Br or I) effect intermolecular sp3C─H metalation of t Bu2‐py bases under mild conditions. The sp3C─H metalated products can be converted in situ into ─BPin, ─iodo, ─bromo and ─hydroxy derivatives for further elaboration. Mechanistic investigations indicate that: i) a frustrated Lewis pair effects sp3C─H heterolysis to form the C─M bond and a protonated pyridine; ii) C─H metalation requires singly halide‐bridged super‐electrophilic M2X6 dimers for sufficiently low barriers. Finally, sp3C─H metalation using M2X6 is not limited to t Bu2‐py bases. Thus, it is important to be aware of this facile sp3C─H functionalisation when using a range of non‐nucleophilic Brønsted bases
Group 13 exchange for catalytic turnover
Get PDFTransition metals are able to undergo redox-active processes, such as oxidative addition and reductive elimination with carbon-element bonds. These two fundamental steps have allowed for the majority of metal-catalysed processes to take place by providing access to multiple oxidation states. Precious metals, such as palladium, platinum, iridium, rhodium, and ruthenium, dominate transition metal catalysis due to their wide applicability and highly tuneable ligands. However, these metals can be toxic and have low abundance in the Earth’s crust, leading to high costs and difficult purification.
Group 13 elements are an attractive alternative to transition metals in catalysis due to their lower toxicity and cost. Group 13 elements are electron-deficient, giving them unique reactivity within the main-group; however, their synthetic utility has been limited to stoichiometric processes. Group 13 elements do not have access to empty d-orbitals, so cannot undergo the same redox-active processes that transition metals can, therefore their applications in catalysis are limited to redox-neutral processes. Therefore, new methods of catalytic turnover are required for the application of group 13 elements in catalysis. Group 13 exchange has been developed as a redox-neutral process for catalytic turnover, whereby classically stoichiometric reactions have been rendered catalytic. Group 13 exchange has been applied to the aluminium-catalysed C‒H borylation of alkynes with HBpin using a tethered Al/N Lewis pair, which shut down the competitive alkyne hydroboration pathway.
Transborylation, group 13 exchange between two boron atoms, has provided access to metal-free catalytic systems by extending traditional stoichiometric borane-mediated reactions. Transborylation has been applied to borane-catalysed hydroboration and reduction, classic stoichiometric reactions that have been rendered catalytic. This work has successfully extended the catalogue of transborylation-mediated catalysis: borane-catalysed C‒F arylation and esterification of alkyl fluorides demonstrated excellent functional group tolerance across a wide range of examples. The borane-catalysed asymmetric hydroboration of alkenes showed promise, with moderate yields and enantioselectivities, and improved the synthesis of chiral borane reagents. The borane-catalysed intramolecular 1,1-carboboration of silylalkynes gave access to a variety of silolenyl boronic esters and was the first example of a borane-catalysed carboboration reaction
The urgency of doing: evaluating the validity of an implementation and sustainability measure for school-wide prevention programs
No full textSchool-based prevention and promotion interventions (SBPPI) teach students how to recognize and manage emotions, solve problems effectively, establish positive relationships with others, and develop prosocial attitudes. When implemented effectively, SBPPI have been shown to improve desirable outcomes (e.g., commitment to community, standardized achievement test scores, and attendance) and to reduce undesirable outcomes (e.g., suspensions, drug and alcohol use, and aggressive and violent behavior). Unfortunately, our understanding of how to effectively implement and sustain SBPPI outside of well-controlled conditions is lacking. In order to help build a science of implementation and sustainability, this thesis presents a conceptual framework and a measurement tool for effective SBPPI implementation. The framework differentiates among various phases of implementation, ecological levels surrounding implementation in schools, and factors in the system of implementation that facilitate fidelity and sustainability. This framework is measured by the “Schools Implementing Towards Sustainability” (SITS) scale, which is designed to be “user-friendly” in field settings by being viable and scalable. Analyses from a diverse sample of 157 schools implementing Social-Emotional Character Development (SECD), a type of SBPPI, reveal that the SITS has good reliability, good concurrent and construct validity, and promising predictive validity. The findings of the SITS may help advance both the science of school-based interventions and the science of implementation and dissemination as a whole by demonstrating how to bridge the science/“real world” gap.M.S.Includes bibliographical referencesby Dominic C. Mocer
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