Strongly Reducing, Visible‐Light Organic Photoredox Catalysts as Sustainable Alternatives to Precious Metals

Abstract

Photoredox catalysis is a versatile approach for the construction of challenging covalent bonds under mild reaction conditions, commonly using photoredox catalysts (PCs) derived from precious metals. As such, there is need to develop organic analogues as sustainable replacements. Although several organic PCs have been introduced, there remains a lack of strongly reducing visible light organic PCs. Herein, we establish the critical photophysical and electrochemical characteristics of both a dihydrophenazine and a phenoxazine system that enables them success as strongly reducing visible light PCs for trifluoromethylations and dual photoredox/nickel catalyzed C-N and C-S cross-couplings, reactions which have been historically exclusive to precious metal PCs.

Recent Advances and Challenges in the Design of Organic Photoacid and Photobase Generators for Polymerizations

“…However, many metal species are considered toxic and their elimination from the final polymer remains an issue. Moreover, metal contamination could limit the use of such polymers in value‐added applications as for instance medical devices, drug delivery systems, or electronics . For this reason, intensive research has been dedicated to the development of metal‐free photoactive compounds for different types of polymerizations, such as free radical polymerization, controlled/living polymerization, and cationic polymerization.…”

Photocatalytic Synthesis of Polycyclic Indolones

“…Given the highly negative reduction potential of NAPs (E red = À1.3 Vv s. SCE), we reasoned that am ore reducing photocatalyst would facilitate a photoinduced electron transfer (PET) to the substrate, thus increasingt he conversion of 2a.T ot his purpose, we performed the reaction in the presence of PC2,ahighly reducing phenoxazine photocatalyst recently developed by Miyake and coworkers (E red* = À1.93 Vv s. SCE). [13] Pleasingly,t he yield of 6a significantly increased to 58 %( entry 2). Based on these results, we then further evaluated fac-Ir(ppy) 3 (E red* = À1.73 Vv s. SCE) which provedt ob eavery efficient photocatalyst for the targeted transformation leadingt o6a in 67 %i solated yield (entry 3).…”

Cottrell Scholars: L. K. Charkoudian, G. M. Miyake, C. Risko, A. M. Spokyny / TREE Awards: M. Gruebele, T. W. Odom und G. C. Shields / Humboldt‐ und Bessel‐Forschungspreise

“…Außerdem interessieren sie sich für die Selbstorganisaton von Blockcopolymeren unter Bildung photonischer Kristalle. In Chemistry—A European Journal berichtete er über stark reduzierende organische Photoredoxkatalysatoren für Prozesse mit sichtbarem Licht . Miyake gehört dem internationalen Beirat von Macromolecular Rapid Communications an.…”