RT Journal Article T1 How dihalogens catalyze michael addition reactions A1 Hamlin, Trevor A1 Fernández López, Israel A1 Bickelhaupt, Matthias AB 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. PB Wiley YR 2019 FD 2019 LK https://hdl.handle.net/20.500.14352/101611 UL https://hdl.handle.net/20.500.14352/101611 LA eng NO 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. NO Netherlands Organization for Scientific Research NO Ministerio de Economía y Competitividad (España) DS Docta Complutense RD 7 abr 2025