Abstract
The creation of new bonds via C-F bond cleavage of readily available per- or oligofluorinated compounds has received growing interest. Using such a strategy, a myriad of valuable partially fluorinated products can be prepared, which otherwise are difficult to make by the conventional C-F bond formation methods. Visible light photoredox catalysis has been proven as an important and powerful tool for defluorinative reactions due to its mild, easy to handle, and environmentally benign characteristics. Compared to the classical C-F activation that proceeds via two-electron processes, radicals are the key intermediates using visible light photoredox catalysis, providing new modes for the cleavage of C-F bonds. In this review, a summary of the visible light-promoted C-F bond cleavage since 2018 was presented. The contents were classified by the fluorosubstrates, including polyfluorinated arenes, gem-difluoroalkenes, trifluoromethyl arenes, and trifluoromethyl alkenes. An emphasis is placed on the discussion of the mechanisms and limitations of these reactions. Finally, my personal perspective on the future development of this rapidly emerging field was provided.
Highlights
The C-F bond is the strongest covalent single bond that carbon can form
This review focuses on the C-F bond cleavage enabled by visible light photoredox catalthe types of fluorosubstrates [32,33]
Bond cleavage alkenes of trifluoromethyl alkenes led to which were readily converted into fluorinated dihydrobenzoxepines by cleaving a second gem-difluoroalkenes, which were readily converted into fluorinated bond in the presence of base
Summary
The C-F bond is the strongest covalent single bond that carbon can form. The strength of the C-F is among the reasons why organofluorine compounds have found wide applications in diverse fields [1,2,3,4]. Due to the unique redox properties of photocatalysts, the direct C-F bond cleavage enables the generation of carbon radicals by either reductive quenching or oxidative quenching of redox properties of photocatalysts, the direct. − and fluorosubstrate generates highly reactive radical anion, which eliminates fluoride to give a carbon radiPC transfer (SET). The presence of electron-withdrawing groups π-systems in the fluorosubstrates are favorable fluorosubstrates are favorable forand accepting an electron from the photocatalyst This activation is suitable for the tivation mode is suitable forphotocatalyst. PC− to bon radical, whichgives can be single-electron reduced ions to form carbon ions to facilitate the fluoride elimination. The C-F bond cleavage of gem-difluoroalkenes and highly fluoriand highly fluorinated arenes has alsovia been reported via this addition-elimination process, nated arenes has been reported this addition-elimination process, depending on depending on photocatalysts and radical precursors that used.
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