Hamlin, TrevorFernández López, IsraelBickelhaupt, Matthias2024-02-212024-02-212019Hamlin, 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.201903196https://hdl.handle.net/20.500.14352/101611We 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.engAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/journal articlehttps://doi.org/10.1002/anie.201903196open access547Química orgánica (Química)2306 Química Orgánica