1,720,961 research outputs found
Triazole formation and the click concept in the synthesis of interlocked molecules
Full text linkThe click concept, as originally discussed by Sharpless, Finn, and Kolb, is both powerful and simple. Kolb et al. suggested that in= the search for functional molecules, chemists should focus on a small set of reactions that proceed in high yield under mild conditions and in high selectivity. Their proposal was that a relatively small number of such methodologies is sufficient to explore chemical space to solve problems in a range of disciplines, an idea pithily contained in their suggestion that chemists can obtain ‘‘diverse chemical function from a few good reactions.’’ In this perspective, we discuss how these ideas are particularly relevant in the context of the synthesis and study of mechanically interlocked molecules (MIMs), which helps to explain why the best-known click reaction, the Cu-mediated alkyne-azide cycloaddition, was adopted so rapidly by the MIM community, and highlight that more explicit application of click concepts could help drive future progress
The final stereogenic unit of [2]rotaxanes: type 2 geometric isomers
Full text linkMechanical stereochemistry arises when the interlocking of stereochemically trivial covalent subcomponents results in a stereochemically complex object. Although this general concept was identified in 1961, the stereochemical description of these molecules is still under development to the extent that new forms of mechanical stereochemistry are still being identified. Here, we present a simple analysis of rotaxane and catenane stereochemistry that allowed us to identify the final missing simple mechanical stereogenic unit, an overlooked form of rotaxane geometric isomerism, and demonstrate its stereoselective synthesis.</p
Dataset for an article: A Chiral Macrocycle for the Stereoselective Synthesis of Mechanically Planar Chiral Rotaxanes and Catenanes
No full textThis dataset supports the publication: A Chiral Macrocycle for the Stereoselective Synthesis of Mechanically Planar Chiral Rotaxanes and Catenanes
AUTHORS: Shu Zhang, Arnau Rodríguez-Rubio, Abed Saady, Graham J. Tizzard, Stephen M. Goldup
JOURNAL: Chem
This dataset contains:
Characterisation data (NMR, MS, x-ray) for all the compounds reported in the manuscript
Licence: CC-BY</span
Dataset in support of the thesis 'Synthesis and applications of mechanically interlocked molecules'
No full textThis dataset contains:
NMR spectra (MNova format), Chemdraw schemes. HPLC and CD spectra, crystallographic data, MS data.
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A chiral macrocycle for the stereoselective synthesis of mechanically planar chiral rotaxanes and catenanes
Full text linkActive-template auxiliary methodologies have previously been developed for the stereoselective synthesis of chiral interlocked molecules in which the mechanical bond provides the sole stereogenic unit. To date however, the covalent auxiliary has been included in the half-axle components (rotaxanes) or pre-macrocycle components (catenanes), and thus mechanically chiral rotaxane and catenane syntheses rely on different chiral components. Here we present a single, simple amino acid-derived macrocycle that mediates the formation of both catenanes and rotaxanes in excellent stereoselectivity. We demonstrate the flexibility of our approach through the stereoselective synthesis of all three isomers of a co-conformationally mechanically planar chiral [3]rotaxane
Facial selectivity in mechanical bond formation: axially chiral enantiomers and geometric isomers from a simple prochiral macrocycle
Full text linkIn 1971, Schill recognized that a prochiral macrocycle encircling an oriented axle led to geometric isomerism in rotaxanes. More recently, we identified an overlooked chiral stereogenic unit in rotaxanes that arises when a prochiral macrocycle encircles a prochiral axle. Here, we show that both stereogenic units can be accessed using equivalent strategies, with a single weak stereodifferentiating interaction sufficient for moderate to excellent stereoselectivity. Using this understanding, we demonstrated the first direct enantioselective (70% ee) synthesis of a mechanically axially chiral rotaxane.</p
Dataset in support of the thesis 'The Hitchhiker's Guide to Mechanical Stereochemistry'
No full textDataset in support of the thesis 'The Hitchhiker's Guide to Mechanical Stereochemistry' containing:
NMR spectra (MNova format), Chemdraw schemes. HPLC and CD spectra, crystallographic data, MS data.
The dataset is composed of three folders, each relating to an individual published research chapter. </span
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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