Recursos de colección

Repositorio Hipermedial UNR - Repositorio Hipermedial de la Universidad Nacional de Rosario (6.314 recursos)

El Repositorio Hipermedial UNR es un repositorio académico abierto creado para archivar, preservar y distribuir digitalmente en variados formatos tanto materiales de enseñanza y aprendizaje (objetos de aprendizaje) como la producción científica de Investigación y Desarrollo (I+D) de los profesores, profesional es e investigadores de la UNR.

Mostrando recursos 1 - 12 de 12

  1. A convenient and eco-friendly cerium(III) chloride-catalysed synthesis of methoxime derivatives of aromatic aldehydes and ketones

    Cortés, Iván; Kaufman, Teodoro Saúl; Bracca, Andrea Beatriz Juana
    The use of CeCl3·7H2O as an efficient and eco-friendly promoter for the convenient synthesis of methoximes derived from aromatic aldehydes and ketones, is reported. The transformations entail the use of equimolar amounts of MeONH2·HCl and NaOAc in EtOH at 50°C, and no special precautions are needed with regard to the presence of oxygen. The scope and limitations of the transformation were studied and a reaction mechanism was proposed.

  2. Education and engagement : key elements to achieve and maintain a world free of chemical weapons

    Suárez, Alejandra Graciela
    Education and outreach are long term strategic tools for the implementation of the Chemical Weapons Convention (CWC) that actively promote the peaceful use of chemistry. Thousands of new chemicals are reported every day; which can render enormous benefits for the common good. However, as with any science, there is always the possibility that chemistry may be misused as it has been done in the past. This work will refer to preliminary initiatives undertaken to address awareness-raising about the multiple uses of chemical substances and the potential dual -use of scientific knowledge which are being implemented in different levels of chemistry...

  3. Development of polymer-supported chiral aminoalcohols derived from biomass and their application to asymmetric alkylation

    Botta, María Celeste; Biava, Hernán D.; Spanevello, Rolando Ángel; Mata, Ernesto Gabino; Suárez, Alejandra Graciela
    A synthetic strategy has been developed for the preparation of immobilized 1,2-aminoalcohols starting from easily available and renewable chiral building blocks. They were tested as chiral ligands for the asymmetric diethylzinc addition to carbonyl compounds. Enantioselectivities were comparable to those observed for non-immobilized analogs. These results provide strong evidence for the flexibility of our approach to generate highly valuable supported chiral ligands derived from cellulose-rich materials.

  4. Experimental and theoretical insights in the alkene–arene intramolecular π-stacking interaction

    Corne, Valeria; Sarotti, Ariel Marcelo; Ramirez de Arellano, Carmen; Spanevello, Rolando Ángel; Suárez, Alejandra Graciela
    Chiral acrylic esters derived from biomass were developed as models to have a better insight in the aryl–vinyl π-stacking interactions. Quantum chemical calculations, NMR studies and experimental evidences demonstrated the presence of equilibriums of at least four different conformations: π-stacked and face-to-edge, each of them in an s-cis/s-trans conformation. The results show that the stabilization produced by the π–π interaction makes the π-stacked conformation predominant in solution and this stabilization is slightly affected by the electron density of the aromatic counterpart.

  5. Expedient approach to 6-bromo-2-isopropylidenecoumaranone, a potential intermediate for the synthesis of TMC-120B, pseudodeflectusin, and Their congeners

    Pergomet, Jorgelina Leonor; Kaufman, Teodoro Saúl; Bracca, Andrea Beatriz Juana
    A straightforward approach toward 6-bromo-2-isopropylidenecoumaranone, a potential intermediate toward alkaloid TMC 120-B, pseudodeflectusin, and other natural products, was reported. The synthetic sequence involved the reaction of 3-bromosalicylaldehyde with chloroacetone and cyclization of the resulting ether to a 2-acetylcoumaranol intermediate. This was followed by sequential methyl Grignard addition and Jones’ oxidation to the corresponding coumaranone, which was dehydrated to the final product with the methanesulfonyl chloride/pyridine reagent. The protection of the coumaranol as the corresponding THP-ether resulted in improved product yields.

  6. Mebendazole crystal forms in tablet formulations : An ATR-FTIR/chemometrics approach to polymorph assignment

    Calvo, Natalia Lorena; Kaufman, Teodoro Saúl; Maggio, Rubén Mariano
    Structural polymorphism of active pharmaceutical ingredients (API) is a relevant concern for the modern pharmaceutical industry, since different polymorphic forms may display dissimilar properties, critically affecting the performance of the corresponding drug products. Mebendazole (MEB) is a widely used broad spectrum anthelmintic drug of the benzimidazole class, which exhibits structural polymorphism (Forms A–C). Form C, which displays the best pharmaceutical profile, is the recommended one for clinical use. The polymorphs of MEB were prepared and characterized by spectroscopic, calorimetric and microscopic means. The polymorphs were employed to develop a suitable chemometrics-assisted sample display model based on the first two principal...

  7. Computational chemistry driven solution to rubriflordilactone B

    Grimblat, Nicolás; Kaufman, Teodoro Saúl; Sarotti, Ariel Marcelo
    The structure of rubriflordilactone B (2) was determined by X-ray crystallography. However, the NMR data of the synthetic sample did not match those reported for 2. It was then suggested that the original sample contained an additional isomer of different solubility, pseudorubriflordilactone B (3), whose structure remained unknown. From theoretical calculations, reexamination of the NMR data, and biogenetic considerations, it is proposed that 3 should be the 16S,17R isomer of 2.

  8. A theoretical study of the Duff reaction : insights into its selectivity

    Grimblat, Nicolás; Sarotti, Ariel Marcelo; Kaufman, Teodoro Saúl; Simonetti, Sebastián Osvaldo
    The Duff reaction is one of the most employed methods for the ortho-formylation of phenols; however, not much is truly known about its mechanism. Using DFT calculations, we disclose the first theoretical study regarding the selectivity-determining step of the reaction. We have found that this stage is governed by a hydrogen bond, that gives rise to a cyclohexa-2,4-dienone intermediate and establishes the position where the formylation will take place. These findings were evaluated by analysis of the reaction outcome of several non-symmetrically substituted phenols.

  9. A convenient approach to an advanced intermediate toward the naturally occurring, bioactive 6-substituted 5-hydroxy-4-aryl-1H-quinolin-2-ones

    Simonetti, Sebastián Osvaldo; Larghi, Enrique Leandro; Kaufman, Teodoro Saúl
    5-Hydroxy-4-aryl-3,4-dihydro-1H-quinolin-2-ones are a small family of natural products isolated from fungal strains of Penicillium and Aspergillus. Most of its members, which are insecticides and anthelmintics, carry an isoprenoid C-6 side chain. The synthesis of a 6-propenyl-substituted advanced intermediate for the total synthesis of these natural products is presented in this paper. This was achieved through the stereoselective construction of a β,β-diarylacrylate derivative from 6-nitrosalicylaldehyde, using a Wittig olefination and a Heck–Matsuda arylation, followed by a selective Fe0-mediated reductive cyclization. Installation of the 6-propenyl side chain was performed by 5-O-allylation of the heterocycle, followed by Claisen rearrangement and conjugative migration of the allyl double bond, as the key...

  10. Efficient total synthesis of neocryptolepine and synthetic access to 6-methylquinindoline from a common intermediate

    Kaufman, Teodoro Saúl; Larghi, Enrique Leandro; Bracca, Andrea Beatriz Juana; Heredia, Daniel Alejandro; Mendez, María Virginia
    A convenient approach toward the indoloquinolines neocryptolepine and 6-methylquinindoline from a common intermediate, is reported. Both sequences, designed for maximum use of accessible reagents and robust conditions, are straightforward and efficient. They involved the amidation of 2- aminobenzaldehyde (prepared by iron-mediated reduction of 2-nitrobenzaldehyde) with 2- nitrophenylacetic acid, followed by a K2CO3-assisted cyclization to form a 3-(2-nitrophenyl)quinolin-2- one as the common precursor. Me2CO3-mediated N-methylation of the lactam, reduction of the nitro moiety and final cyclization resulted in 55% overall yield of neocryptolepine, whereas cyclocondensation and N-methylation afforded 79% overall yield of 6-methyl quinindoline. Thus, the sequences toward the targets entailed two POCl3-promoted C–N bond forming reactions, two Fe-mediated...

  11. Efficient total synthesis of neocryptolepine and synthetic access to 6-methylquinindoline from a common intermediate

    Kaufman, Teodoro Saúl; Larghi, Enrique Leandro; Bracca, Andrea Beatriz Juana; Heredia, Daniel Alejandro; Mendez, María Virginia
    A convenient approach toward the indoloquinolines neocryptolepine and 6-methylquinindoline from a common intermediate, is reported. Both sequences, designed for maximum use of accessible reagents and robust conditions, are straightforward and efficient. They involved the amidation of 2- aminobenzaldehyde (prepared by iron-mediated reduction of 2-nitrobenzaldehyde) with 2- nitrophenylacetic acid, followed by a K2CO3-assisted cyclization to form a 3-(2-nitrophenyl)quinolin-2- one as the common precursor. Me2CO3-mediated N-methylation of the lactam, reduction of the nitro moiety and final cyclization resulted in 55% overall yield of neocryptolepine, whereas cyclocondensation and N-methylation afforded 79% overall yield of 6-methyl quinindoline. Thus, the sequences toward the targets entailed two POCl3-promoted C–N bond forming reactions, two Fe-mediated...

  12. First total synthesis of the only known 2- isopropyliden-2H-benzofuran-3-one isolated from V. luetzelburgii

    Kaufman, Teodoro Saúl; Bracca, Andrea Beatriz Juana; Larghi, Enrique Leandro; Pergomet, Jorgelina Leonor
    The first total synthesis of 5-(1-hydroxy-1-ethyl)-2-isopropyliden-2H-benzofuran-3-one, is reported in its racemic and in one of its optically active [(S)-( )] forms. This heterocycle, isolated from Verbesina luetzelburgii, is the only known 2-isopropyliden-2H-benzofuran-3-one produced by species of Verbesina. The sequence took place in eight steps and 19% overall yield (up to 33% for the chiral form), from 40-hydroxyacetophenone. It entailed carbonyl group protection as the 1,3-dioxolane and a phenol ortho formylation, followed by a Williamson etherification with chloroacetone and an organocatalytic cross-aldolization, to afford a 2-acetyl-2,3-dihydrobenzofuran-3-ol intermediate. The latter underwent a methyl Grignard addition to the carbonyl moiety, followed by selective oxidation of the benzylic alcohol and deprotection, resulting...

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