Copper-catalyzed silylation of p-quinone methides: New entry to dibenzylic silanes

An efficient and general copper(i)-catalyzed silylation of p-quinone-methides is described. Non-symmetric dibenzylic silanes are obtained in high yields under mild reaction conditions. These compounds can be used as bench-stable benzylic carbanion precursorsWe thank the European Research Council (ERC-337776) and MINECO (CTQ2012-35957) for financial support. M. T. and A. P. thank MICINN for RyC and JdC contract

Stereoselective traceless borylation–allenation of propargylic epoxides: dual role of the copper catalyst

This is the peer reviewed version of the following article: Chemistry: A European Journal 23.69 (2017): 17478 –17481, which has been published in final form at http://doi.org/10.1002/chem.201705019. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingChiral α-allenols are prepared with high diastereocontrol through an unprecedented and spontaneous β-oxygen elimination of an α-epoxy vinyl boronate. Stochiometric experiments and DFT calculations support a dual role of the copper catalyst, which orchestrates the hydroboration and the syn-elimination stepThe European ResearchCouncil (ERC-337776) and MINECO (CTQ2016-78779-R) for financial support M.T.thanks MICINNfor a RyC contrac

Enantiospecific Synthesis of 1,3-Disubstituted Allenes from Propargylic Carbonates through a Borylation-1,2-Elimination Process

An array of enantioenriched vinyl boronates bearing an allylic carbonate moiety have been prepared through selective hydroboration of propargyl carbonates. Treatment of these vinyl boronates with TBAF in THF affords enantioenriched 1,3- disubstituted allenes through a novel 1,2-anti elimination in good yields and high enantiospecificitiesWe thank MINECO (CTQ2016-78779-R) and MICINN (PID2019-107380GB I00) for financial suppor

Nuevas reacciones de borilación catalizadas por cobre en la síntesis de boranatos dibencílicos y alenos

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid. Facultad de Ciencias. Departamento de Química Orgánica. Fecha de lectura: 16-07-2018Esta tesis tiene embargado el acceso al texto completo hasta el 16-01-202

Selective Reductive Dimerization of CO 2 into Glycolaldehyde

International audienceThe selective dimerization of CO2 into glycolaldehyde is achieved in a one-pot two-step process via formaldehyde as a key intermediate. The first step concerns the iron-catalyzed selective reduction of CO2 into formaldehyde via formation and controlled hydrolysis of a bis(boryl)acetal compound. The second step concerns the carbene-catalyzed C–C bond formation to afford glycolaldehyde. Both carbon atoms of glycolaldehyde arise from CO2 as proven by the labeling experiment with 13CO2. This hybrid organometallic/organic catalytic system employs mild conditions (1 atm of CO2, 25 to 80 °C in less than 3 h) and low catalytic loadings (1 and 2.5%, respectively). Glycolaldehyde is obtained in 53% overall yield. The appealing reactivity of glycolaldehyde is exemplified (i) in a dimerization process leading to C4 aldose compounds and (ii) in a tri-component Petasis–Borono–Mannich reaction generating C–N and C–C bonds in one process

Borohydride Compounds Catalyze the Selective 4e – Reduction of CO 2 with 9-BBN

International audienceThe selective double hydroboration of CO2 into bis(boryl)acetal (BBA) is a challenging yet appealing reduction process since BBA can be used as a versatile C1 and Cn sources for the synthesis of value-added products. In the present study, we demonstrate that simple borohydride compounds are efficient and selective catalysts for the synthesis of BBA when using 9-borabicyclo(3.3.1)nonane (9-BBN) as a reductant. The experimental and theoretical investigations show that while the borohydride species catalyzes the first reduction step of CO2 into formoxyborane (2e– reduction intermediate), the observed 4e– reduction selectivity is mostly due to the ability of 9-BBN to reduce the formoxyborane into BBA without a catalyst. Notably, 0.2 mol % of LiH2BBN catalyzed the hydroboration of CO2 with 9-BBN as a reductant into the corresponding BBA in 77% yield with TON and TOF of 385 and 196 h–1, respectively. The simplicity of borohydride contrasts with the more elaborate catalytic systems used so far for the 4e– reduction of CO2

CO 2 Hydroboration: Impact of the Boryl Moieties on the Reactivity of Four Bis(boryl)acetal Compounds toward 2,6‐Diisopropylaniline

International audienceThe hydroboration of CO2 into bis(boryl)acetal (BBA) compounds is an important transformation, since it enabled to selectively reduce CO2 by 4e- and to subsequently use the BBA compounds as C1 and Cn sources. However, the influence of the nature of the boryl moieties on the reactivity of BBA compounds has not been evaluated so far. In the present study, four BBA compounds – including two new ones – were reacted with 2,6-diisopropylaniline to afford the expected imine. Significant differences in the rate of the reaction from minutes to weeks have been observed depending on the BBA used, showing the importance of the nature of the boryl moieties. Theoretical investigations enabled to propose a mechanism involving the addition of the aniline to the BBA as the rate-determining step and to determine that the steric hindrance of the BBA compounds is the main factor driving the rate of this condensation reaction

Copper-Catalyzed Borylative Aromatization of <i>p</i>‑Quinone Methides: Enantioselective Synthesis of Dibenzylic Boronates

In this report, we establish that DM-Segphos copper­(I) complexes are efficient catalysts for the enantioselective borylation of <i>para</i>-quinone methides. This method provides straightforward access to chiral monobenzylic and dibenzylic boronic esters, with enantiomeric ratios up to 96:4, using a commercially available chiral phosphine. Standard manipulations of the C–B bond afford a variety of chiral diaryl derivatives

Naturaleza de las Prácticas Profesionales. Caso CECAR

Las Prácticas Profesionales de la Corporación Universitaria del Caribe–CECAR, hacen parte de los programas académicos, por lo que todo futuro egresado ha de realizar el curso de Práctica Profesional. La práctica de un estudiante universitario es fundamental para fortalecer competencias y habilidades necesarias para el buen ejercicio profesional, ya que con esta tiene la oportunidad de conocer la realidad laboral y de esta forma fortalecer sus conocimientos. En este sentido, las prácticas profesionales permiten que el futuro profesional sume experiencias a partir de la interacción con contextos reales, donde tenga la oportunidad de aplicar los conocimientos adquiridos durante todo el proceso de formación. Estas experiencias le proporcionan al estudiante elementos para su crecimiento personal y profesional, es por ello que, en CECAR, la práctica, además de tener un componente curricular, es concebida como un proceso de aprendizaje continuo donde el estudiante afianza sus competencias funcionales: saber, saber hacer y ser/convivir (Tobón, 2006); desarrolla habilidades blandas y fortalece sus saberes. El presente libro tiene como finalidad ilustrar al lector sobre la naturaleza y especificidades de las prácticas profesionales de algunos de los programas académicos de CECAR, atendiendo a que cada programa posee características y elementos pedagógicos que le permiten al estudiante, en calidad de profesional en formación, desempeñarse de manera óptima en contextos reales de aprendizaje. Así también, se plantean los actores de la práctica teniendo en cuenta sus distintos roles, la articulación de las prácticas con el factor identitario del programa académico, sus características y su relación con el sector externo