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Developing sustainable strategies for the construction of heterocycles and cyano-functionalization
Full text linkThis thesis presents the development of novel synthetic methods for the preparation
of various nitrogen-containing heterocycles and polyheterocycles, utilizing greener
and more sustainable methodologies. It also explores new electrochemical
cyanation protocols that employ safer cyanide sources and/or milder reaction
conditions.
The Introduction emphasizes the significance of heterocyclic compounds in
everyday chemistry, briefly discussing their applications in pharmaceuticals and
industry.
Chapter 1 introduces the isoindolinone core and its biological properties. The
importance of cascade procedures in the synthesis of isoindolinone derivatives is
also highlighted, with a particular focus on electrochemical methods. The chapter
first details an electro-induced cascade reaction for synthesizing 3-N-aryl
substituted isoindolinones using catalytic amounts of current and supporting
electrolyte. The method was then extended to synthesize isoindolinone-containing
polyheterocycles exploiting the second reactivity of suitable electrophilic moieties
at the ortho-position of the reagents. Finally, the chapter concludes by describing a
one-pot cascade protocol for preparing a C-10-substituted batracylin analog using
Cs2CO3, as the solely catalyst. A preliminary photophysical characterization of the
attained analog is also reported.
Chapter 2 discusses the importance of nitrile group in organic chemistry, outlining
the limitations of traditional cyanation protocols and the consequent need for safer
cyanide sources and greener methods. Two novel electrochemical cyanation
reactions are described: the cyanation of chalcones and imines through the catalytic
electrochemical activation of acetone cyanohydrin, as cyanating agent; the
exploration of the 5-aminotetrazole as a novel and safer CN surrogate, capable of
generating both electrophilic and nucleophilic cyanide for the cyanation of a large
range of substrates. This latter method was also optimized in flow-electrochemical
systems.
Chapter 3 explores the advantages of combining of the Pictet-Spengler and Ugi four
component reactions for the first synthesis of 4-imidazolidinone-tetrahydro-β
carboline hybrids by means of TMSOTf as an effective mediator
Gold Salts as Alternative Catalysts in Promoting Cascade Condensation of 2-Aminobenzaldehydes with Alcohols and Amines
No full textThe distinctive features of gold self-relay catalysts were alternatively utilized in the intriguing cascade condensation of 2-aminobenzaldehydes with alcohols and amines. Using NaAuCl4·2H2O as a catalyst, a range of 13-alkyloxy-7,11b-dihydro-6H,13H-6,12-[1,2]benzenoquinazolino[3,4-a]quinazoline derivatives was produced in good to high yields through A3B condensation of various 2-aminobenzaldehydes with alcohols. By carefully choosing the reaction conditions, gold catalysis also proved effective for A2B condensation with primary aryl- and benzylamines, facilitating the synthesis of challenging McGeachin bisaminals, including a chiral nonracemic derivative of 2-(S)-methylbenzylamine. The mild conditions of this gold-catalyzed approach may lead to new advancements in the field
Unrevealing the Nitrogen Elusive Chirality of 3‐Sulfanyl and 3‐Sulfinyl N‐Tosyl Isoindolinones by ECD Spectra: An Experimental and Theoretical Investigation
No full textThe nitrogen–hybridization/pyramidalization of two solvated N-tosylisoindolinone derivatives having chiral residues in adjacent (I) or adjacent and distal (II) position has been investigated by a theoretical-computational procedure based on Molecular Dynamics simulations and Quantum–Chemical calculations. After validation of our methodology in providing a reliable repertory of conformations by modeling the electronic circular dichroism (EDC) spectra, the electronic features associated with N-pyramidalization were further characterized through Natural Bond Order (NBO) analysis. Comparing against the N-geometry observed in crystal structures as a reference, our findings reveal that the presence of neighbouring chiral centers induces a more pronounced N-pyramidalization in solution than in the solid state, both in I and II. Furthermore, NBO analysis confirms that the N-lactam mostly retains the sp2 character but exhibits slight configurational distortion (ξI=13°; ξII=21°), which significantly influences the chiroptical activities observed in ECD spectra of I and II. This substantiates the N-lactams as configurationally stable chiral centers
Electrochemical-Induced Cascade Reaction of 2-Formyl Benzonitrile with Anilines: Synthesis of N-Aryl Isoindolinones
Full text linkAn electrochemical initiated tandem reaction of anilines with 2-formyl benzonitrile has been developed. Thus, unprecedented 3-N-aryl substituted isoindolinones have been conveniently achieved by constant current electrolysis in a divided cell using catalytic amount of electricity and supporting electrolyte and a Pt-cathode as working electrode. The origin of the electrochemical activation as well as the mechanism of the subsequent chemical cascade reactions have been investigated by DFT calculations
Expanding Diversity of Fused Steroid-Quinoline Hybrids by Sequential Amination/Annulation/Aromatization Reactions
Full text linkViable alternative approaches to a variety of ring A
and ring D-fused steroid-quinoline hybrids, along with ring A, Dfused,
and/or ring A-fused, side chain-substituted steroid-bisquinolines
were explored by means of sequential amination/
annulation/aromatization reactions of suitable ketosteroids with 2-
acyl-substituted anilines. Key factors directing the chemoselective
behavior of polyfunctionalized substrates were investigated.
Remarkably, the use of TMSOTf as an alternative promoter/
catalyst enabled the direct synthesis of the desired hybrids,
avoiding the protection/deprotection steps of the conventional
procedures when the starting substrates contained labile functional
groups
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
Product Selectivity Control in the Brønsted Acid-Mediated Reactions with 2-Alkynylanilines
Full text linkBr & oslash;nsted acid-catalysed/mediated reactions of the 2-alkynylanilines are reported. While metal-catalysed reactions of these valuable building blocks have led to the establishment of robust protocols for the selective, diverse-oriented syntheses of significant heterocyclic derivatives, we here demonstrate the practical advantages of an alternative methodology under metal-free conditions. Our investigation into the key factors influencing the product selectivity in Br & oslash;nsted acid-catalysed/mediated reactions of 2-alkynylanilines reveals that different reaction pathways can be directed towards the formation of diverse valuable products by simply choosing appropriate reaction conditions. The origins of chemo- and regioselectivity switching have been explored through Density Functional Theory (DFT) calculations
Diastereoselective Synthesis of High Functionalized 4‐Imidazolidinone‐Tetrahydro‐β‐Carboline Hybrids via Divergent Post‐Ugi Transformation
Full text linkAn easily scalable and highly diastereoselective synthesis of challenging 1,2,5,6,11,11b-hexahydro-3H-imidazo[1′,2′:1,2]pyrido[3,4-b]indol-3-ones is accomplished through divergent transformation of Ugi 4-CR products. The trimethylsilyl trifluoromethanesulfonate (TMSOTf) mediated intramolecular condensation of a series of Ugi 4-CR adducts generates a N-acylimidinium intermediate which undergoes ring closure to selectively afford the target title compounds in good to high yields
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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