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oai:docta.ucm.es:20.500.14352/1016182024-08-20T23:56:26Zcom_20.500.14352_14col_20.500.14352_15

Origin of rate enhancement and asynchronicity in iminium catalyzed Diels–Alder reactions Vermeeren, Pascal Hamlin, Trevor Fernández López, Israel Bickelhaupt, Matthias 547 Addition reactions Aldehydes Catalysts Molecular orbitals Numerical methods Olefins Química orgánica (Química) 2306 Química Orgánica This work was supported by the Netherlands Organization for Scientic Research (NWO), Dutch Astrochemistry Network (DAN), and the Spanish MINECO (CTQ2016-78205-P, CTQ2016-81797-REDC and PID2019-106184GB-I00). The Diels-Alder reactions between cyclopentadiene and various α,β-unsaturated aldehyde, imine, and iminium dienophiles were quantum chemically studied using a combined density functional theory and coupled-cluster theory approach. Simple iminium catalysts accelerate the Diels-Alder reactions by lowering the reaction barrier up to 20 kcal mol-1 compared to the parent aldehyde and imine reactions. Our detailed activation strain and Kohn-Sham molecular orbital analyses reveal that the iminium catalysts enhance the reactivity by reducing the steric (Pauli) repulsion between the diene and dienophile, which originates from both a more asynchronous reaction mode and a more significant polarization of the π-system away from the incoming diene compared to aldehyde and imine analogs. Notably, we establish that the driving force behind the asynchronicity of the herein studied Diels-Alder reactions is the relief of destabilizing steric (Pauli) repulsion and not the orbital interaction between the terminal carbon of the dienophile and the diene, which is the widely accepted rationale Netherlands Organization for Scientic Research Dutch Astrochemistry Network Ministerio de Economía y Competitividad (España) Depto. de Química Orgánica Fac. de Ciencias Químicas TRUE pub 2024-02-21T09:05:32Z 2024-02-21T09:05:32Z 2020 journal article VoR https://hdl.handle.net/20.500.14352/101618 2041-6520 10.1039/d0sc02901g eng info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020/PID2019-106184GB-I00/ES/UNA APROXIMACION DIFERENTE PARA ENTENDER Y CONTROLAR LA CATALISIS/ CTQ2016-78205-P CTQ2016-81797-REDC Vermeeren, P., Hamlin, T. A., Fernández, I., & Bickelhaupt, F. M. (2020). Origin of rate enhancement and asynchronicity in iminium catalyzed Diels–Alder reactions. Chemical Science, 11(31), 8105-8112. Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ open access application/pdf Royal Society of Chemistry