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How dihalogens catalyze michael addition reactions Hamlin, Trevor Fernández López, Israel Bickelhaupt, Matthias 547 Química orgánica (Química) 2306 Química Orgánica We have quantum chemically analyzed the catalytic effect of dihalogen molecules (X2 = F2, Cl2 , Br2, and I2) on the aza-Michael addition of pyrrolidine and methyl acrylate using relativistic density functional theory and coupled-cluster theory. Our state-of-the-art computations reveal that activation barriers systematically decrease as one goes to heavier dihalogens, from 9.4 kcalmol@1 for F2 to 5.7 kcalmol@1 for I2. Activation strain and bonding analyses identify an unexpected physical factor that controls the computed reactivity trends, namely, Pauli repulsion between the nucleophile and Michael acceptor. Thus, dihalogens do not accelerate Michael additions by the commonly accepted mechanism of an enhanced donor– acceptor [HOMO(nucleophile) LUMO(Michael acceptor)] interaction, but instead through a diminished Pauli repulsion between the lone-pair of the nucleophile and the Michael acceptorQs p-electron system. Netherlands Organization for Scientific Research Ministerio de Economía y Competitividad (España) Depto. de Química Orgánica Fac. de Ciencias Químicas TRUE pub 2024-02-21T08:12:18Z 2024-02-21T08:12:18Z 2019 journal article VoR https://hdl.handle.net/20.500.14352/101611 XXXX-XXXX 10.1002/anie.201903196 eng CTQ2016-78205-P Hamlin, Trevor A., et al. «How Dihalogens Catalyze Michael Addition Reactions». Angewandte Chemie International Edition, vol. 58, n.o 26, junio de 2019, pp. 8922-26. https://doi.org/10.1002/anie.201903196. Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ open access application/pdf Wiley