How Lewis Acids Catalyze Diels-Alder Reactions.
How Lewis Acids Catalyze Diels-Alder Reactions.
Angew Chem Int Ed Engl. 2020 Jan 16;:
Authors: Vermeeren P, Hamlin TA, Fernández I, Bickelhaupt FM
Abstract
The Lewis acid (LA)-catalyzed Diels-Alder reaction between isoprene and methyl acrylate was investigated quantum chemically using a combined density functional theory and coupled-cluster theory approach. Computed activation barriers systematically decrease as the strength of the LA increases along the series I 2 < SnCl 4 < TiCl 4 < ZnCl 2 < BF 3 < AlCl 3 . Emerging from our activation strain and Kohn-Sham molecular orbital bonding analysis was an unprecedented finding, namely that the LAs accelerate the Diels-Alder reaction by a diminished Pauli repulsion between the p - electron systems of the diene and dienophile. Our results oppose the widely accepted view that LAs catalyze the Diels-Alder reaction by enhancing the donor-acceptor [HOMO diene -LUMO dienophile ] interaction and constitute a novel physical mechanism for this indispensable textbook organic reaction.
PMID: 31944503 [PubMed - as supplied by publisher]
Source: Angewandte Chemie - Category: Chemistry Authors: Vermeeren P, Hamlin TA, Fernández I, Bickelhaupt FM Tags: Angew Chem Int Ed Engl Source Type: research