Hydroxylamine Derivatives as Nitrogen‐Radical Precursors in Visible‐Light Photochemistry

Abstract

In recent years, hydroxylamines derivatives have been exploited as nitrogen-radical precursors in visible-light photochemistry. Their ability to serve as electrophores in redox chemistry has propelled the development of many novel transformations. Fundamental mechanistic aspects as well as the importance in the preparation of nitrogen-containing molecules will be highlighted.

Photosensitized Intermolecular Carboimination of Alkenes through the Persistent Radical Effect

“…[17] Additionally,the high reactivity of iminyl radicals has been utilized in ap lethora of 1,5hydrogen atom transfer (HAT) reactions. [18,19] In all of these cases,i minyl radicals are first generated from oxime esters through as ingle electron transfer (SET) event ( Figure 1B, left). [19] Alternatively,o xime esters have also been employed successfully in the photosensitized generation of iminyl radicals through NÀOb ond homolysis.…”

“…[18,19] In all of these cases,i minyl radicals are first generated from oxime esters through as ingle electron transfer (SET) event ( Figure 1B, left). [19] Alternatively,o xime esters have also been employed successfully in the photosensitized generation of iminyl radicals through NÀOb ond homolysis. [20] Recently,w eh ave utilized this distinctive energy transfer (EnT) pathway to develop ageneral radical decarboxylation process applicable to both aromatic and aliphatic carboxylic acids ( Figure 1B, right).…”

Radical‐Promoted C−C Bond Cleavage: A Deconstructive Approach for Selective Functionalization

“…[54] Unlike transition metal catalysed processes,p hotoredox catalysis can use either reductive SET or oxidative SET approaches for NÀObond homolysis,thus enabling access to abroad range of products. [54] Unlike transition metal catalysed processes,p hotoredox catalysis can use either reductive SET or oxidative SET approaches for NÀObond homolysis,thus enabling access to abroad range of products.…”

Exploiting Imine Photochemistry for Masked N-Centered Radical Reactivity

“…Circumventing this limitation would require another means of accessing open-shell character at nitrogen (see Figure 1B). [24,25] Prominent alternatives to amine radical cations include amidyl or imidyl radicals arising from oxidation of N À Hbonds [26,27] via proton-coupled electron transfer (PCET) [28] or from NÀXb onds via homolysis, [29][30][31] reduction, [32] or even oxidation [33] by employing a-aminoxy carboxylic acid auxiliaries popularized by the groups of Leonori [34,35] and Studer. [24,25] Prominent alternatives to amine radical cations include amidyl or imidyl radicals arising from oxidation of N À Hbonds [26,27] via proton-coupled electron transfer (PCET) [28] or from NÀXb onds via homolysis, [29][30][31] reduction, [32] or even oxidation [33] by employing a-aminoxy carboxylic acid auxiliaries popularized by the groups of Leonori [34,35] and Studer.…”