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Computational Investigation of the Role Played by Rhodium(V) in the Rhodium(III)‐Catalyzed ortho ‐Bromination of Arenes
Author(s) -
Zhang Tao,
Qi Xiaotian,
Liu Song,
Bai Ruopeng,
Liu Chao,
Lan Yu
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201605188
Subject(s) - rhodium , halogenation , chemistry , catalytic cycle , substituent , reductive elimination , catalysis , oxidative addition , reactivity (psychology) , medicinal chemistry , electronic effect , organic chemistry , medicine , alternative medicine , pathology
In this study, M11‐L was used to evaluate the feasibility of the formation of rhodium(V) species using the rhodium(III)‐catalyzed ortho ‐bromination of arenes as a model reaction. In most cases for these types of reactions, DFT calculations reveal that the bromination step involves a Br transfer from N ‐bromosuccinimide to the reacting arylrhodium to form a bromonium intermediate, followed by a Br shift to generate a new C−Br bond, which is more favorable than the previously proposed Rh III /Rh V catalytic cycle. The rhodium catalyst remains in its +3 oxidation state throughout. The substituent effects of the reacting arene were studied, and computational results showed that the introduction of electron‐donating groups on the reacting arene was favorable for this pathway. In contrast, the inclusion of a strong electron‐withdrawing group on the aromatic ring would hinder the formation of a bromonium intermediate. Therefore, the Rh III /Rh V catalytic cycle is favorable in cases that involve a Rh V intermediate, which is generated by oxidative addition with NBS. In this pathway, the C−Br bond is formed by reductive elimination from the Rh V intermediate. Additionally, a distortion–interaction analysis model along the reaction pathway was used to explain the directing‐group effects. The results showed that the interaction energy controlled the reactivity because of the difference in electronic nature of various directing groups.