Radical reactions promoted by trivalent tertiary phosphines

Abstract

<p>The background and recent breakthroughs in the single-electron-transfer (SET) reactions with trivalent tertiary phosphines are summarized and discussed in detail, and an outlook in the developments within this field is provided.</p>

Phosphorus-Based Catalysis

“…Organophosphorus compound-mediated SET processes have received much less attention than their nitrogen counterparts, despite trivalent phosphine radical cations and phosphoranyl radicals having been recognized as reaction intermediates as early as the 1950s . Progress in this emerging field has established that organophosphorus compounds can act as radical initiators, catalysts, and radical precursors in various SET transformations for the synthesis of important structural motifs. , With the rapid development of photocatalysis in recent years, the use of organophosphorus compounds as radical precursors, especially for the purpose of deoxygenation or desulfurization, is becoming established as a reliable method . Several examples of organophosphorus compound-mediated radical processes are discussed below.…”

“…In addition to their roles as radical initiators and catalysts as described above, trivalent phosphorus­(III) compounds are increasingly being used as radical precursors for SET transformations . Although, at present, stoichiometric reagents (e.g., as ylide or phosphine) are required, the byproducts formed in the deoxygenation or desulfurization process may be recycled in situ, as we have discussed above regarding phosphine oxide catalysis.…”

“…In addition to those phosphorus-mediated reactions that operate under mechanisms involving electron pair transfer, phosphorus compound-mediated single-electron transfer (SET) processes are a promising, yet undeveloped, area. Because of the rapid development and growing interest in photochemistry and electrochemistry in recent years, studies of organophosphorus compound-mediated SET processes are gaining momentum …”

Phosphorus Compounds as Precursors and Catalysts for Radical C−C Bond‐Forming Reactions

“…radicals and their addition to unsaturated compounds is a useful method for the formation of C−P bonds [11] . Phosphorus compounds have also been used as radical chain carriers to generate carbon‐centered radicals from organohalides and xanthates [11b] . In addition, chiral phosphonate catalysts have been used to impart enantioselectivity in radical reactions [12] .…”

Application of Bifunctional 2-Amino-1,4-naphthoquinones in Visible-Light-Promoted Photocatalyst-Free Alkene Perfluoroalkyl-Alkenylation

“…In addition, organic dyes could also serve as photosensitizers to activate the carbon–iodine bond of perfluoroalkyl iodides under visible light irradiation (Scheme B) . In addition to transition-metal complexes and organic dyes, amines were employed as photomediators to activate perfluoroalkyl iodides, affording a variety of perfluoroalkylation products (Scheme C). , Very recently, visible-light-induced tertiary phosphine-catalyzed activation of perfluorobutyl iodide was successfully applied in perfluoroalkylation (Scheme D) . Although the aforementioned visible-light-promoted perfluoroalkylation presented many remarkable advantages, additional catalysts or photomediators, such as transition-metal complexes, organic dyes, amines, or phosphines, were required for activation of perfluoroalkyl iodides.…”