In this paper, we present an unprecedented and general umpolung protocol that allows the functionalization of silyl enol ethers and of 1,3‐dicarbonyl compounds with a large range of heteroatom ...nucleophiles, including carboxylic acids, alcohols, primary and secondary amines, azide, thiols, and also anionic carbamates derived from CO2. The scope of the reaction also extends to carbon‐based nucleophiles. The reaction relies on the use of 1‐bromo‐3,3‐dimethyl‐1,3‐dihydro‐1λ3d1,2iodaoxole, which provides a key α‐brominated carbonyl intermediate. The reaction mechanism has been studied experimentally and by DFT, and we propose formation of an unusual enolonium intermediate with a halogen‐bonded bromide.
A useful strategy: Herein, we report an umpolung strategy mediated by a hypervalent iodine(III) reagent for the functionalization of enol derivatives with different heteronucleophiles including carboxylic acids, thiols, alcohols, primary and secondary amines, azides and carbamates generated from CO2. Relevant examples for the derivatization of natural products and pharmaceutical compounds are also presented. The mechanism of the reaction was investigated by DFT calculations and experimental studies.
3-Fluoro- and trifluoromethylthio-piperidines represent important building blocks for discovery chemistry. We report a simple and efficient method to access analogs of these compounds that are armed ...with rich functionality allowing them to be chemoselectively derivatized with high diastereocontrol.
We have used experimental studies and DFT calculations to investigate the IrIII‐catalyzed isomerization of allylic alcohols into carbonyl compounds, and the regiospecific isomerization–chlorination ...of allylic alcohols into α‐chlorinated carbonyl compounds. The mechanism involves a hydride elimination followed by a migratory insertion step that may take place at Cβ but also at Cα with a small energy‐barrier difference of 1.8 kcal mol−1. After a protonation step, calculations show that the final tautomerization can take place both at the Ir center and outside the catalytic cycle. For the isomerization–chlorination reaction, calculations show that the chlorination step takes place outside the cycle with an energy barrier much lower than that for the tautomerization to yield the saturated ketone. All the energies in the proposed mechanism are plausible, and the cycle accounts for the experimental observations.
Experimental and DFT calculations have been used to understand the mechanism of the IrIII‐catalyzed isomerization of allylic alcohols into carbonyl compounds, and the regiospecific isomerization–chlorination of allylic alcohols into α‐chlorinated carbonyl compounds. The results presented, point to the importance of using an experimental–computational approach to comprehend the mechanisms of complex reactions (see scheme).
A new generation of chiral gold(I) catalysts based on variations of complexes with JohnPhos-type ligands with a remote C 2-symmetric 2,5-diarylpyrrolidine have been synthesized with different ...substitutions at the top and bottom aryl rings: from replacing the phosphine by a N-heterocyclic carbene (NHC) to increasing the steric hindrance with bis- or tris-biphenylphosphine scaffolds, or by directly attaching the C 2-chiral pyrrolidine in the ortho-position of the dialkylphenyl phosphine. The new chiral gold(I) catalysts have been tested in the intramolecular 4+2 cycloaddition of arylalkynes with alkenes and in the atroposelective synthesis of 2-arylindoles. Interestingly, simpler catalysts with the C 2-chiral pyrrolidine in the ortho-position of the dialkylphenyl phosphine led to the formation of opposite enantiomers. The chiral binding pockets of the new catalysts have been analyzed by DFT calculations. As revealed by non-covalent interaction plots, attractive non-covalent interactions between substrates and catalysts direct specific enantioselective folding. Furthermore, we have introduced the open-source tool NEST, specifically designed to account for steric effects in cylindrical-shaped complexes, which allows predicting experimental enantioselectivities in our systems.
Chiral γ-branched aliphatic amines are present in a large number of pharmaceuticals and natural products. However, enantioselective methods to access these compounds are scarce and mainly rely on the ...use of designed chiral transition-metal complexes. Herein, we combined an organocatalytic method for the stereospecific isomerization of chiral allylic amines with a diastereoselective reduction of the chiral imine/enamine intermediates, leading to γ-trifluoromethylated aliphatic amines with two noncontiguous stereogenic centers, in excellent yields and high diastereo- and enantioselectivities. This approach has been used with primary amine substrates. This approach also provides a new synthetic pathway to chiral trifluoromethylated scaffolds, of importance in medicinal chemistry. Additionally, a gram-scale reaction demonstrates the applicability of this synthetic procedure.
We have used experimental studies and DFT calculations to investigate the Ir
-catalyzed isomerization of allylic alcohols into carbonyl compounds, and the regiospecific isomerization-chlorination of ...allylic alcohols into α-chlorinated carbonyl compounds. The mechanism involves a hydride elimination followed by a migratory insertion step that may take place at Cβ but also at Cα with a small energy-barrier difference of 1.8 kcal mol
. After a protonation step, calculations show that the final tautomerization can take place both at the Ir center and outside the catalytic cycle. For the isomerization-chlorination reaction, calculations show that the chlorination step takes place outside the cycle with an energy barrier much lower than that for the tautomerization to yield the saturated ketone. All the energies in the proposed mechanism are plausible, and the cycle accounts for the experimental observations.
Víctor García Vázquez nos habla de la aún poca difusión que ha tenido la poesía chiapaneca en sus voces y lenguas autóctonas. Así, el autor refiere los nuevos intentos, de principios del siglo, para ...que los lectores tengan proximidad con la literatura en lenguas originarias. Por esto, en esta ocasión, resalta la participación de poetas de mujeres provenientes de Chiapas, en específico, hablará acerca de Ruperta Bautista Vázquez, Juana Karen Peñate, Mikeas Sánchez y de Enriqueta Lunez.
A la par de los estudios enfocados a la literatura, es necesario realizar análisis literarios transdisciplinarios que abarquen los aspectos textuales desde las ciencias sociales. Desde el campo de ...las letras, Emiliano Pérez Cruz presenta una crítica y denuncia al sistema capitalista que provoca la marginación de los sujetos de clase baja o los sin-lugar. Los términos de violencia objetiva y subjetiva propuestos por Slavoj Zizek ayudarán a analizar la realidad de estos individuos, su periferia y su reclusión en la marginalidad producto de la misma sociedad a la que pertenecen. El objetivo de este es observar que la violencia objetiva, en sus formas sistémica y simbólica, determina la trayectoria de vida y el contexto social de los personajes principales, incluso más que la violencia subjetiva.Along with studies focused on literature, it is necessary to carry out transdisciplinary literary analyzes that cover the textual aspects from the social sciences. From the field of letters, Emiliano Pérez Cruz presents a critique and denunciation of the capitalist system that provokes the marginalization of the subjects of the lower class or the non-place. The terms of objective and subjective violence proposed by Slavoj Zizek will help to analyze the reality of these individuals, their periphery and their seclusion in the periphery product of the same society to which they belong. The objective of this is to observe that objective violence, in its systemic and symbolic forms, determines the trajectory of life and the social context of the main characters, even more than subjective violence.
Along with studies focused on litera-ture, it is necessary to carry out trans-disciplinary literary analyzes that cov-er the textual aspects from the social sciences perspective. From the field of ...letters, Emiliano Pérez Cruz presents a critique of the capitalist system as a cause of marginalization for low-class or displaced population. The terms of objective and subjective violence pro-posed by Slavoj Zizek are used by the authors to analyze the reality of these people, their periphery and their seclu-sion in marginality as a product of the same society to which they belong.The objective of this work is to ob-serve that objective violence, in its sys-temic and symbolic forms, determines the life trajectory and social context of the main characters, even more than subjective violence.
A la par de los estudios enfocados en la literatura, es necesario realizar aná-lisis literarios transdisciplinarios que abarquen los aspectos textuales desde las ciencias sociales. Desde el campo de las letras, Emiliano Pérez Cruz pre-senta una crítica al sistema capitalista como causa de marginación de los su-jetos de clase baja o los sin-lugar. Los términos de violencia objetiva y sub-jetiva propuestos por Slavoj Zizek son utilizados por los autores para analizar la realidad de estas personas, su pe-riferia y su reclusión en la marginali-dad producto de la misma sociedad a la que pertenecen. El objetivo de este trabajo es observar que la violencia ob-jetiva, en sus formas sistémica y simbó-lica, determina la trayectoria de vida y el contexto social de los personajes principales, incluso más que la violen-cia subjetiva.
A regioselective protocol for the synthesis of substituted allylic chlorides, bromides, and fluorides has been established. Remarkably, the method can be applied to the enantioselective synthesis of ...challenging chiral allylic chlorides. When the allylic halides are treated with the base triazabicyclodecene as the catalyst, a 1,3-proton shift takes place, giving the corresponding vinyl halides in excellent yields with excellent
:
ratios. Furthermore, the 1,3-proton shift takes place with an outstanding level of chirality transfer from chiral allylic alcohols (≤98%) to give chiral trifluoromethylated vinyl chlorides.
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