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: Tags: Angew Chem Int Ed Engl Source Type: research
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