Overcoming Photochemical Limitations in Metallaphotoredox Catalysis: Red-Light-Driven C-N Cross-Coupling

J Am Chem Soc. 2022 Dec 14;144(49):22409-22415. doi: 10.1021/jacs.2c09745. Epub 2022 Nov 23.

Abstract

Aryl amination is an essential transformation for medicinal, process, and materials chemistry. In addition to classic Buchwald-Hartwig amination conditions, blue-light-driven metallaphotoredox catalysis has emerged as a valuable tool for C-N cross-coupling. However, blue light suffers from low penetration through reaction media, limiting its scalability for industrial purposes. In addition, blue light enhances unwanted side-product formation in metallaphotoredox catalysis, namely hydrodehalogenation. Low-energy light, such as deep red (DR) or near-infrared (NIR), offers a solution to this problem as it can provide enhanced penetration through reaction media as compared to higher-energy wavelengths. Herein, we show that low-energy light can also enhance the desired reactivity in metallaphotoredox catalysis by suppressing unwanted hydrodehalogenation. We hypothesize that the reduced side product is formed by direct photolysis of the aryl-nickel bond by the high-energy light, leading to the generation of aryl radicals. Using deep-red or near-infrared light and an osmium photocatalyst, we demonstrate an enhanced scope of (hetero)aryl bromides and amine-based nucleophiles with minimal formation of hydrodehalogenation byproducts.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amination
  • Bromides / chemistry
  • Catalysis
  • Light*
  • Nickel* / chemistry

Substances

  • Nickel
  • Bromides