Radical Cations of Phenyl‐Substituted Aziridines: What Are the Conditions for Ring Opening?

Abstract

Abstract:Radical cations were generated from different phenyl-substituted aziridines by pulse radiolysis in aqueous solution containing TlOH In the pulse radiolysis experiments in aqueous solution, the primary oxidants can also be observed,whereas in n-butyl chloride a transient at 325 nm remains unidentified. In the Laser Flash experiments, both types of radical cations were also observed.

Evidence for Ligand‐Centered Reactivity of a 17e Radical Cationic 2H‐Azaphosphirene Complex

“…[14] We monitored the ring expansion reaction of 1 + 2d Ǟ 3d (Scheme 2) at different concentrations of [FcH]PF 6 by using 31 P{ 1 H} NMR spectroscopy ( Figure 1). These series revealed that the reaction progression depends strongly on the amount of [FcH]PF 6 6 , the curves show a steep ascending slope after a comparably flat trend at the start, and again a flattening at the end. As no resonances other than those of 1 and 3d were detected by 31 P{ 1 H} NMR spectroscopic monitoring during the reaction course, the time dependent decrease of 1 follows the same trend as the increase of 3d.…”

“…Obviously, 0.01 equiv. of [FcH]PF 6 is not sufficient for the successful initiation of the chain reaction ( Figure 1). In contrast to 2a-e, the reaction of 1 with HCN (2f) proceeded much more slowly and was unselective.…”

“…Thus, upon pulse radiolysis or 60 Co γ radiolysis, phenylaziridines either form transient radical cations with retention of the closed ring structure or undergo ring opening with formation of radical cationic azomethine ylides depending on their substitution patterns. [6] Although the spin density of most organometallic radicals is localized mainly at the metal center, organometallic radicals can show both metal-centered and/or ligand-centered reactivity, whereas 17e cationic complexes often show the latter behavior. [7] For the generation of radical cations in solution four major routes are currently in use: (1) anodic oxidation, (2) photoinduced electron transfer (PET), (3) oxidation by radicals generated by pulse or γ radiolysis, and (4) chemical oxidation.…”

Photochemistry of Reactive Intermediates

“…In this way we have studied several photoinduced ring-opening reactions of radical cations containing three- [17][18][19][20][21] or four-membered rings [22][23][24][25], phototautomerizations of ionized ketones and enols [26][27][28], and rotamer inter-conversions in polyene radical cations [29][30][31]. I will use two examples to illustrate the photochemistry of radical cations:…”

Strong Evidence for an Unprecedented Borderline Case of Dissociation and Cycloaddition in Open‐Shell 1,3‐Dipole Chemistry: Transient Nitrilium Phosphane‐Ylide Complex Radical Cations

“…(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) reported SET oxidations of aziridines to form transient azomethine ylide radical cations [4] that can yield five-membered heterocycles as final products, thus behaving as openshell 1,3-dipoles. Scheme 1.…”