Issue 3, 2020

Brønsted acid catalysis of photosensitized cycloadditions

Abstract

Catalysis is central to contemporary synthetic chemistry. There has been a recent recognition that the rates of photochemical reactions can be profoundly impacted by the use of Lewis acid catalysts and co-catalysts. Herein, we show that Brønsted acids can also modulate the reactivity of excited-state organic reactions. Brønsted acids dramatically increase the rate of Ru(bpy)32+-sensitized [2 + 2] photocycloadditions between C-cinnamoyl imidazoles and a range of electron-rich alkene reaction partners. A combination of experimental and computational studies supports a mechanism in which the Brønsted acid co-catalyst accelerates triplet energy transfer from the excited-state [Ru*(bpy)3]2+ chromophore to the Brønsted acid activated C-cinnamoyl imidazole. Computational evidence further suggests the importance of driving force as well as geometrical reorganization, in which the protonation of the imidazole decreases the reorganization penalty during the energy transfer event.

Graphical abstract: Brønsted acid catalysis of photosensitized cycloadditions

Supplementary files

Article information

Article type
Edge Article
Submitted
25 9 2019
Accepted
01 12 2019
First published
02 12 2019
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2020,11, 856-861

Brønsted acid catalysis of photosensitized cycloadditions

E. M. Sherbrook, H. Jung, D. Cho, M. Baik and T. P. Yoon, Chem. Sci., 2020, 11, 856 DOI: 10.1039/C9SC04822G

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