Issue 17, 2021

Mechanistic studies of Cp*Ir(iii)/Cp*Rh(iii)-catalyzed branch-selective allylic C–H amidation: why is Cp*Ir(iii) superior to Cp*Rh(iii)?

Abstract

Density functional theory calculations have revealed the mechanism and origins of the reactivity and regioselectivity of the Cp*Ir(III)/Cp*Rh(III)-catalyzed allylic C–H amidation of alkenes and dioxazolones. Generally, the catalytic cycle consists of alkene coordination, C(sp3)−H activation, dioxazolone oxidative addition, reductive elimination and proto-demetallation to give the final amidation product. The C–H activation is found to be the rate-determining step, and it controls the reactivity of the reaction. For the Cp*Ir(III)-catalyzed system, the C–H activation undergoes an Ir(III)-assisted proton transfer process with a low energy barrier, elucidating its high reactivity. In contrast, the C–H activation step is more like a direct deprotonation in the Cp*Rh(III)-catalyzed system, which is responsible for its higher barrier and lower reactivity. The branched-selectivity arises from the electronic effect of the alkyl group on the charge distribution over the allylic moiety. Herein, iridium(V) polarizes the allylic group greater than that of the rhodium(V) system, which accounts for its good regioselectivity. The mechanistic insights will be useful for the further development of transition metal-catalyzed selective C–H amination reactions.

Graphical abstract: Mechanistic studies of Cp*Ir(iii)/Cp*Rh(iii)-catalyzed branch-selective allylic C–H amidation: why is Cp*Ir(iii) superior to Cp*Rh(iii)?

Supplementary files

Article information

Article type
Paper
Submitted
07 mars 2021
Accepted
06 avr. 2021
First published
06 avr. 2021

Org. Biomol. Chem., 2021,19, 3850-3858

Mechanistic studies of Cp*Ir(III)/Cp*Rh(III)-catalyzed branch-selective allylic C–H amidation: why is Cp*Ir(III) superior to Cp*Rh(III)?

N. Ma, Z. Liu, J. Huang and Y. Dang, Org. Biomol. Chem., 2021, 19, 3850 DOI: 10.1039/D1OB00446H

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements