期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 58, 期 26, 页码 8922-8926出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201903196
关键词
activation strain model; density functional calculations; halogen bonding; Michael addition; Pauli repulsion; reactivity
资金
- Netherlands Organization for Scientific Research (NWO)
- Spanish MINECO [CTQ2016-78205-P, CTQ2016-81797-REDC]
We have quantum chemically analyzed the catalytic effect of dihalogen molecules (X-2=F-2, Cl-2, Br-2, and I-2) 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 9.4kcalmol(-1) for F-2 to 5.7kcalmol(-1) for I-2. 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 acceptor's pi-electron system.
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