Advances in Photocatalysis: A Microreview of Visible Light Mediated Ruthenium and Iridium Catalyzed Organic Transformations

Abstract

Photocatalytic organic transformations utilizing ruthenium and iridium complexes have garnered significant attention due to the access they provide to new synthetic spaces through new reaction mechanisms. A survey of the photophysical data and the diversity of transformations that may be accomplished utilizing commercially available photocatalysts is contained herein.

Positionelle und geometrische Isomerisierung von Alkenen: der Gipfel der Atomökonomie

“…Die gleiche Gruppe konnte zudem die Vielseitigkeit dieses Aktivierungsmodus durch Kombination mit einer C-F-Alkenylierung zeigen. [68] Inspiriert durch den Sehzyklus von Säugetieren entwickelte diese Gruppe eine kontra-thermodynamische Isomerisierung polarisierter Alkene,k atalysiert durch (À)-Riboflavin (Vitamin B 2 ). [69]…”

A Fully Automated Continuous‐Flow Platform for Fluorescence Quenching Studies and Stern–Volmer Analysis

“…These results seemed logical considering that Ir(ppy) 3 is the only photocatalyst with an excited state oxidation potential ( E 1/2 Ir 4+ /Ir* 3+ =−1.73 V) sufficient for the direct reduction of phthalimide 4 ( E red =−1.57 V vs. SCE, see SI) 16. We also found that inexpensive organic photocatalysts 4CzIPN and 2CzPN both showed quenching in presence of protonated isoquinoline, while no quenching was observed with isoquinoline alone 18.…”

“…We chose to investigate the Ir(ppy) 3 ‐catalyzed photocatalytic decarboxylation of α,β‐unsaturated carboxylic acids, a reaction developed in our laboratory (Scheme 5 A) 15. By comparing the excited state potentials of Ir(ppy) 3 ( E 1/2 Ir 4+ /Ir* 3+ =−1.73 V and E 1/2 Ir* 3+ /Ir 2+ =0.31 V vs. SCE) with the reduction potentials of BrCF 2 COOEt ( E red =−0.57 V vs. SCE, see SI) and cinnamic acid ( E red =−1.09 V vs. SCE, see SI), we reasoned that the reaction would most likely proceed through the oxidative quenching of the fluorinating agent, thus generating the CF 2 COOEt radical of interest 16. Nevertheless, due to the extremely high excited state oxidation potential of Ir(ppy) 3 , we were curious to probe whether the reduction of cinnamic acid, albeit unexpected, could take place (Scheme 5 B).…”

“…SCE, see SI) and cinnamic acid (E red = À1.09 Vv s. SCE, see SI), we reasoned that the reaction would most likely proceed through the oxidative quenching of the fluorinating agent, thus generating the CF 2 COOEt radical of interest. [16] Nevertheless,d ue to the extremely high excited state oxidation potential of Ir(ppy) 3 , we were curious to probe whether the reduction of cinnamic acid, albeit unexpected, could take place (Scheme 5B). Thus, we performed as eries of automated Stern-Volmer experiments to determine the rate at which ethyl bromodifluoroacetate or cinnamic acid can quench the excited state of Ir(ppy) 3 .T he results obtained are summarized in Scheme 5C (for the Stern-Volmer plots see SI).…”

Selective Synthesis of Z‐Cinnamyl Ethers and Cinnamyl Alcohols through Visible Light‐Promoted Photocatalytic E to Z Isomerization

“…[13] Of which, visible-light-mediated E!Z isomerization of simple alkenes can be achieved by using photosensitizers as a safe and clean energy source (Scheme 1b). [14] This approach has significant appeal both in terms of atom economy and environmentally benign nature.I nr ecent years, photocatalysts such as iridium-base triplet photosensitisers, [15] organic dyes such as riboflavin, [16] aromatic keto compounds such as 2-iodo-9-fluorenone, [17] and covalent organic frameworks (COF) [18] have been employed to promote the E to Z isomerization of alkenes (Scheme 1b). Detailed investigations by Weaver,R ueping, Gilmour,W ang, Balaraman and others, carefully delineated the sensitized isomerization mechanisms and deliveredt he E to Z isomerization of stilbenes, [15b, 17, 18] allylamines, [15a] a,b-unsaturatede sters, [15d, 16a] cinnamonitriles, [16c] allylic alcohols, [19] styrenyl boron species [15f] andv inyl silanes.…”