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Amino Alcohols and Diamines: Novel Syntheses of Enantiopure Molecules useful in Catalysis
No full textThe subject of this PhD thesis is in the synthesis of new chiral amino alcohols and diamines using several strategies. In the first part has been reported the syntheses, the attribution of absolute configuration and the spectroscopic characterization of new chiral diamines, amino alcohols and polyfunctionalized ligands based on monoterpenes backbone, in particular (-)-limonene and (+)-3-carene. In the second part of this thesis were reported new synthetic strategies to obtain several functionality through Betti type reactions, using different starting materials and reaction's conditions. Thank to these new synthetic variants it was possible to obtain chiral arylglycinates, a class of unnatural amino acids, aminocicloalyl naphthols and phenols, used as chiral ligands in asymmetric synthesis, chiral bifunctionalized (thio)ureas, largely applied as organocatalysts, benzochromenes, a class of biologically active compounds with a wide spectrum of activities and widely employed as cosmetics, pigments and potential biodegradable agrochemicals, and diamino alkyl naphthols, potentially useful as catalyst in asymmetric synthesis. Moreover, have been applied some Betti's bases as catalysts in the enantioselective addition of diethyl zinc on α,Î2-unsaturated carbonyl compounds and in the reduction of prochiral ketones with borane, both with good yields but with moderate enantiomeric excesses. Finally, in the last part of this thesis has been proposed a new synthetic route to obtain 4-fluorothreonine, a fluorinated natural amino acid, through a greener and simpler way than that known in the literature
Application of Enantiopure1-(Aminoalkyl)naphthols and 2-(Aminoalkyl)phenols in the Enantioselective Addition of Organozinc to a,b-Unsatured Carbonyl Compounds
No full textA convenient synthesis of new diamine, aminoalcohol and aminophosphines chiral auxiliaries based on limonene oxide
No full textA strategy for the synthesis of new chiral auxiliaries based upon vicinal diamines, amino alcohols and aminophosphines, obtained from limonene oxide, has been developed. The methodology allows the preparation of (1R,2R,4S)-1-methyl-4-(prop-1-en-2-yl)cyclohexane-1,2-diamine starting from a commercially available mixture of cis/trans (4S)-(-)-limonene oxides, through a stereoconvergent synthetic sequence. The process starts from an inexpensive naturally occurring material, is amenable to scale-up and allows easy access to highly useful enantiopure building blocks and ligands, employed in asymmetric catalysis
Borane-Mediated Asymmetric Reduction of Acetophenone by Enantiopure Aminonaphthols and Aminoalcohols as Catalytic Source
No full textPractical, cheap, and stereoselective synthetic methods were applied to the preparation of novel 1-(aminoalkyl)naphthol and g-aminoalcohol tridentate ligands. The ligands obtained were conveniently applied with good results as catalytic sources in the borane-mediated enantioselective reduction of acetophenone with borane dimethylsulfide. Conformational analysis through molecular modeling allows the rationalization of observed stereochemical outcomes
Novel stereoselective synthesis of 2,3-dihydro-1H-benzo[f]chromen-3-amine derivatives through a one-pot three-component reaction
No full textA short and stereoselective novel synthesis of benzo[f]chromen-3-amine derivatives in good yields, through a three-component aromatic Betti type reaction under solvent free conditions is reported. The spontaneous reaction occurs in the absence of acid catalysts. The use of chiral 1-phenylethylamine or alpha,beta-unsaturated aldehydes allowed us to prepare enantiopure benzo[f]chromen-3-amine derivatives with good stereoselectivity. Conformational analysis compared with the 1H-NMR data of the products obtained, allowed us to the determine the absolute configuration, which was also confirmed by X-ray analysis
Stereoselective synthesis of new vicinal diaminoalkyl naphthols by three component Mannich type reaction of alpha,beta-unsaturated aldehydes
No full textThe application of the aromatic Mannich reaction to alpha,beta-unsaturated aldehydes, affords a series of new diaminoalkyl naphthols, by a convenient solventless reaction, starting from inexpensive and easily avail-able starting materials. The absolute configurations of the products obtained are attributed on the basis of the coupling constant values of 1H-NMR spectra, joined with the conformational analysis of the molecules by molecular modelling. A mechanistic hypothesis is proposed, which involves an imino–amino intermediate
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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