Zusammenfassung
Photoredox catalysis (PRC) has gained enormous and wide-ranginginterest in recent years but has also been subject to significantmechanistic uncertainty, even controversy. To provide a method bywhich the missing understanding can begin to be filled in, we demonstrateherein that it is possible to isolate as authentic materials the one-electronreduction products of representative PRC catalysts ...
Zusammenfassung
Photoredox catalysis (PRC) has gained enormous and wide-ranginginterest in recent years but has also been subject to significantmechanistic uncertainty, even controversy. To provide a method bywhich the missing understanding can begin to be filled in, we demonstrateherein that it is possible to isolate as authentic materials the one-electronreduction products of representative PRC catalysts (PCs). Specifically,KC8 reduction of both 9,10-dicyanoanthracene and a naphthalenemonoamide derivative in the presence of a cryptand provides convenientaccess to the corresponding [K(crypt)(+)][PC & BULL;-] salts as clean materials that can be fully characterized by techniquesincluding EPR and XRD. Because PC & BULL;- statesare key intermediates in PRC reactions, such isolation allows forhighly controlled study of these anions' specific reactivityand hence their mechanistic roles. As a demonstration of this principle,we show that these salts can be used to conveniently interrogate themechanisms of recent, high-profile "conPET" and "e-PRC"reactions, which are currently the subject of both significant interestand acute controversy. Using very simple experiments, we are ableto provide striking insights into these reactions' underlyingmechanisms and to observe surprising levels of hidden complexity thatwould otherwise have been very challenging to identify and that emphasizethe care and control that are needed when interrogating and interpretingPRC mechanisms. These studies provide a foundation for the study ofa far broader range of questions around conPET, e-PRC, and other PRCreaction mechanisms in the future, using the same strategy of PC & BULL;- isolation.
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