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DFT Mechanistic Study on Palladium‐Catalyzed Redox‐Neutral Hydroarylation of Unactivated Alkenes with Arylboronic Acids
Author(s) -
Zhou Jianguo,
Zhou Yongzhu,
Li Yanxia,
Zhang Jie,
Zhang Lei
Publication year - 2021
Publication title -
asian journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.846
H-Index - 44
eISSN - 2193-5815
pISSN - 2193-5807
DOI - 10.1002/ajoc.202000647
Subject(s) - transmetalation , chemistry , palladium , chelation , regioselectivity , reductive elimination , combinatorial chemistry , aryl , catalysis , functional group , substrate (aquarium) , medicinal chemistry , organic chemistry , alkyl , oceanography , geology , polymer
Density functional calculations were carried out on the mechanism of a palladium‐catalyzed hydroarylation reaction of β,γ‐unsaturated carbonyl compounds with arylboronic acids reported by Engle's group. The proposed reaction pathway consists of several key mechanistic steps, including the chelation of substrate 1 a , transmetalation of organoboron 2 a , migratory insertion, protodepalladation, and dechelation of product 3 a , among which the transmetalation step is rate‐determining with a free‐energy barrier of 27.0 kcal/mol. Experimental researchers proposed that the chelation of Daugulis's 8‐aminoquinoline (AQ) directing group facilitated the desired hydroarylation in a γ‐selective manner. However, the present study revealed that the chelation of AQ indeed retarded the delivery of the aryl group to the double bond and the regioselectivity was not necessarily the result of this group. Indeed, it could effectively prevent the homocoupling of 2 a , because the homocoupling was predicted to be easier than the desired hydroarylation in the absence of AQ. Additionally, some reductive coupling pathways between 1 a and 2 a were designed, and the competition of them was discussed in great detail. Lastly, the extension of this synthetic strategy to other types of alkenes was predicted.