Visible‐Light‐Mediated 5‐exo‐dig Cyclizations of Amidyl Radicals

Abstract

A visible-light-mediated synthesis of 5-methylenepyrrolidinones is reported. This constitutes to the first reported

Visible-Light-Mediated Amination of π-Nucleophiles with N-Aminopyridinium Salts

“…4 Up to date developments in photoredox catalysis 5 indicate that nitrogen radicals can be generated under mild reaction conditions from stable starting materials including phtalimides, [6][7] sulfonamides, [8][9][10] hydrazones, [11][12][13] or aryloxyamides. [14][15][16] There are, however, few examples of using N-aminopyridinium salts as particularly convenient radical precursors due to the simplicity of their large-scale synthesis from commercially available pyrilium salts and hydrazine derivatives or from N-aminopyridinium iodide and acid chlorides, shelf life stability, and a variety of compatible protecting groups of the amine functionality. Photochemically generated amidyl radicals easily react with arenes, heteroarenes, 16 and styrene derivatives [18][19] enabling, among others, the facile synthesis of vicinal aminoalcohols, 20 imidazolines or oxazolines.…”

Anion–π Interactions in Light‐Induced Reactions: Role in the Amidation of (Hetero)aromatic Systems with Activated N‐Aryloxyamides

“…[15,16] Recently,L eonori and co-workersh ave reported how hydroxylamine deriva-tives can efficiently serve as nitrogen-centered radical precursors [17] in photochemical transformations, [18] which are mediated either by different kinds of photocatalysto rb yt he formation of EDA complexes, [19] sometimes in the presenceo fa ni norganic base (K 2 CO 3 ). [20] Sincem ultiply-charged anions,s uch as carbonate, are privileged actors in anion-p interactions, we wondered whether an anion-p interaction might enablet he light-mediated formation of amidyl radicals.A side from conceptual and practicala spects,t his new activation mode might offer an ew opportunity to harnesst he synthetic applicability of amidyl radicals for buildingu pm olecular complexity.I nt his communication, we present evidencef or:( i) the formation of an anion-p complex betweenc arbonate and an electron-poor N-aryloxy amide, (ii)weakening of the NÀOb ond through this interaction, and (iii)directc leavageo ft his bond after singleelectron transfer (SET) induced by visible light, resulting in an amidyl radical that can be trapped in eitheri ntermolecular or intramolecular fashionb ye lectron-rich aromatic substrates. As the first test of our hypothesis, we studied the behavior of the 2,4-dinitro-substituted aryloxya mide 1a in the presence of K 2 CO 3 in acetonitrile( MeCN) solution.I nterestingly,U V/Vis spectra showed ad ramatic enhancement in the absorption be-tween4 25 and 450 nm (Figure 1, red trace).…”

Electrophilic Aminating Agents in Total Synthesis

“…Amidyl radicals have found extensive use in synthesis due to their high reactivity, functional group tolerance and profoundly electrophilic character [248, 257–262] . However, their high reactivity presents challenges because competitive intramolecular H‐atom abstraction reactions can often occur in preference to the target C−N bond formation [256, 263] .…”