Mechanism and Applications of the Photoredox Catalytic Coupling of Benzyl Bromides

Gyurim Park; Seung Yeon Yi; Jaehun Jung; Eun Jin Cho; Youngmin You

doi:10.1002/chem.201603517

Mechanism and Applications of the Photoredox Catalytic Coupling of Benzyl Bromides

Chemistry. 2016 Dec 5;22(49):17790-17799. doi: 10.1002/chem.201603517. Epub 2016 Oct 28.

Authors

Gyurim Park¹, Seung Yeon Yi², Jaehun Jung³, Eun Jin Cho⁴, Youngmin You⁵

Affiliations

¹ Department of Food Science and Engineering, Ewha Womans University, Seoul, 03760, Republic of Korea.
² Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 03760, Republic of Korea.
³ Department of Applied Chemistry, Hanyang University, Ansan, 15588, Republic of Korea.
⁴ Department of Chemistry, Chung-Ang University, Seoul, 06974, Republic of Korea.
⁵ Division of Chemical Engineering and Materials Science, Ewha Womans University, Seoul, 03760, Republic of Korea.

PMID: 27791290
DOI: 10.1002/chem.201603517

Abstract

The photoredox catalytic coupling of halomethyl arenes to bibenzyl derivatives has been demonstrated. The catalytic protocol employed the Hantzsch ester, potassium phosphate, and a photoactive cyclometalated Ir^III complex catalyst. A photochemical quantum yield as high as 20 % was obtained. The catalytic mechanism was investigated in detail by performing photophysical and electrochemical measurements, as well as by quantum chemical calculations. The results suggest that two-electron mediation might be responsible for the improved photon economy. The reaction protocol was compatible with halomethyl arenes that contain a variety of functional groups. Finally, the synthetic utility of our protocol was demonstrated by the preparation of a natural dihydrostilbenoid, brittonin A.

Keywords: Hantzsch ester; bibenzyl; organic chemistry; photochemistry; radical coupling.