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Hamlin, Trevor Fernández López, Israel Bickelhaupt, Matthias 2024-02-21T08:12:18Z 2024-02-21T08:12:18Z 2019 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. 10.1002/anie.201903196 https://hdl.handle.net/20.500.14352/101611 https://doi.org/10.1002/anie.201903196 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. eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 International How dihalogens catalyze michael addition reactions journal article