Studies leading to the development of a single-electron transfer (SET) photochemical strategy for syntheses of macrocyclic polyethers, polythioethers, and polyamides

Advancements in Desilylation Reactions for the Synthesis of Valuable Organic Molecules

Silicon, due to its abundance, non-toxicity, and cost-effectiveness, is a critical element in the earth's crust with significant industrial applications. In organic chemistry, main group elements, and in particular silicon, are extensively utilized as versatile synthetic intermediates. Despite the current challenges associated with harsh reaction conditions and unsustainable practices in synthesizing crucial organic structural molecules, desilylation reactions have emerged as a facilitative method, offering milder conditions and operational simplicity. This review provides a comprehensive analysis of recent advancements in the synthesis of valuable organic molecules through two distinct desilylation reactions. It systematically presents the synthesis of a variety of derivatives, such as furan, alcohol, N-heterocyclic, and ketone, highlighting the broad substrate tolerance of these reactions. This broad functional group compatibility suggests a promising future for the synthesis of a wide range of bioactive molecules, underscoring the significant potential of desilylation in contemporary organic synthesis.

Triplet Energy Transfer (EnT)-Promoted 1,3-Dipolar Cycloaddition Reactions of N-(Trimethylsilyl)methylphthalimide with Electron-Deficient Alkynes and Alkenes

Triplet energy transfer (EnT)-promoted photochemical pathways, arisen by visible light and its photosensitizers, have gained significant attention as a complementary strategy for initiating organic transformations in photochemical reactions that are unlikely to occur through a single electron transfer (SET) process. In the present study, we investigated the triplet EnT-promoted 1,3-dipolar cycloaddition reactions of N-(trimethylsilyl)methylphthalimide with electron-deficient alkynyl and alkenyl dipolarophiles. The triplet excited state of N-(trimethylsilyl)methylphthalimide, promoted by the triplet EnT from thioxanthone (TXA) photosensitizer, underwent sequential intramolecular SET and carbon-to-oxygen migration of the silyl group to form azomethine ylide. This generated ylide cycloadded to alkynes or alkenes to regioselectively and stereospecifically produce a nitrogen-containing benzopyrrolizidine scaffold with multiple stereogenic centers. Crucially, the stereoselectivity of these cycloaddition reactions (i.e., endo versus exo addition) was influenced by the nature of the dipolarophiles.

Visible light driven photoredox/nickel-catalyzed stereoselective synthesis of Z- or E-vinyl thioethers from thiosilane and terminal alkynes

A new method for the synthesis of anti-Markovnikov Z- or E-vinyl thioethers from thiosilane and terminal alkynes under visible-light-induced photoredox/nickel dual catalysis conditions is described. With a judicious choice of a simple nickel catalyst and a ligand, this strategy enables efficient and divergent access to both Z- or E-vinyl thioethers from the same set of simple starting materials. Notably, the approach is free of odorous thiol and has excellent compatibility with functional groups and substrate scope.

Organic Photoredox Reactions in Two-Molecule Photoredox System

Using our recent relevant results, this account shows the featured reactivities of two-molecule photoredox systems compared to one-molecule photoredox systems. The low efficiency of electron transfer processes, such as photoinduced and back-electron transfer, in the two-molecule photoredox system, furnishes unique products through different pathways. The facile replacement of photoredox catalysts with appropriate oxidation/reduction potentials in this system provides valuable insights into photoredox reactions.

Direct Arylation of Distal and Proximal C(sp3)-H Bonds of t-Amines with Aryl Diazonium Tetrafluoroborates via Photoredox Catalysis

A visible light-mediated arylation protocol for t-amines has been reported through the coupling of γ- and α-amino alkyl radicals with different aryl diazonium salts using Ru(bpy)₃Cl₂·6H₂O as a photocatalyst. Structurally different 9-aryl-9,10-dihydroacridine, 1-aryl tetrahydroisoquinoline, hexahydropyrrolo[2,1-a]isoquinoline, and hexahydro-2H-pyrido[2,1-a]isoquinoline frameworks with different substitution patterns have been synthesized in good yield using this methodology.

Recent Advances in Photoredox-Mediated Radical Conjugate Addition Reactions: An Expanding Toolkit for the Giese Reaction

Photomediated Giese reactions are at the forefront of radical chemistry, much like the classical tin-mediated Giese reactions were nearly forty years ago. With the global recognition of organometallic photocatalysts for the mild and tunable generation of carbon-centered radicals, chemists have developed a torrent of strategies to form previously inaccessible radical intermediates that are capable of engaging in intermolecular conjugate addition reactions. This Review summarizes advances in photoredox-mediated Giese reactions since 2013, with a focus on the breadth of methods that provide access to crucial carbon-centered radical intermediates that can engage in radical conjugate addition processes.

Photochemical Methods for Peptide Macrocyclisation

Photochemical reactions have been the subject of renewed interest over the last two decades, leading to the development of many new, diverse and powerful chemical transformations. More recently, these developments have been expanded to enable the photochemical macrocyclisation of peptides and small proteins. These constructs benefit from increased stability, structural rigidity and biological potency over their linear counterparts, providing opportunities for improved therapeutic agents. In this review, an overview of both the established and emerging methods for photochemical peptide macrocyclisation is presented, highlighting both the limitations and opportunities for further innovation in the field.

Control of Chemoselectivity of SET-Promoted Photoaddition Reactions of Fullerene C60 with α-Trimethylsilyl Group-Containing N-Alkylglycinates Yielding Aminomethyl-1,2-dihydrofullerenes or Fulleropyrrolidines

Knowledge about factors that govern chemoselectivity is pivotal to the design of reactions that are utilized to produce complex organic substances. In the current study, single-electron transfer (SET)-promoted photoaddition reactions of fullerene C₆₀ with both trimethylsilyl and various alkyl group-containing glycinates and ethyl N-alkyl-N-((trimethylsilyl)methyl)glycinates were explored to evaluate how the nature of N-alkyl substituents of glycinate substrates and reaction conditions govern the chemoselectivity of reaction pathways followed. The results showed that photoreactions of C₆₀ with glycinates, performed in deoxygenated conditions, produced aminomethyl-1,2-dihydrofullerenes efficiently through a pathway involving the addition of α-amino radical intermediates that are generated by sequential SET-solvent-assisted desilylation of glycinate substrates to C₆₀. Under oxygenated conditions, photoreactions of glycinate substrates, except N-benzyl-substituted analogues, did not take place efficiently owing to quenching of ³C₆₀* by oxygen. Interestingly, N-benzyl-substituted glycinates did react under these conditions to form fulleropyrrolidines through a pathway involving 1,3-dipolar cycloaddition of in situ formed azomethine ylides to C₆₀. The ylide intermediates were formed by regioselective H-atom transfer from glycinates by singlet oxygen. Furthermore, methylene blue (MB)-photosensitized reactions of C₆₀ with glycinates under oxygenated conditions took place efficiently to produce fulleropyrrolidines independent of the nature of N-alkyl substituents of glycinates.

Cross-Electrophile Coupling of Unactivated Alkyl Chlorides

Alkyl chlorides are bench-stable chemical feedstocks that remain among the most underutilized electrophile classes in transition metal catalysis. Overcoming intrinsic limitations of C(sp³)-Cl bond activation, we report the development of a novel organosilane reagent that can participate in chlorine atom abstraction under mild photocatalytic conditions. In particular, we describe the application of this mechanism to a dual nickel/photoredox catalytic protocol that enables the first cross-electrophile coupling of unactivated alkyl chlorides and aryl chlorides. Employing these low-toxicity, abundant, and commercially available organochloride building blocks, this methodology allows access to a broad array of highly functionalized C(sp²)-C(sp³) coupled adducts, including numerous drug analogues.

Highly Diastereoselective Functionalization of Piperidines by Photoredox-Catalyzed α-Amino C-H Arylation and Epimerization

We report a photoredox-catalyzed α-amino C-H arylation reaction of highly substituted piperidine derivatives with electron-deficient cyano(hetero)arenes. The scope and limitations of the reaction were explored, with piperidines bearing multiple substitution patterns providing the arylated products in good yields and with high diastereoselectivity. To probe the mechanism of the overall transformation, optical and fluorescent spectroscopic methods were used to investigate the reaction. By employing flash-quench transient absorption spectroscopy, we were able to observe electron transfer processes associated with radical formation beyond the initial excited-state Ir(ppy)₃ oxidation. Following the rapid and unselective C-H arylation reaction, a slower epimerization occurs to provide the high diastereomer ratio observed for a majority of the products. Several stereoisomerically pure products were resubjected to the reaction conditions, each of which converged to the experimentally observed diastereomer ratios. The observed distribution of diastereomers corresponds to a thermodynamic ratio of isomers based upon their calculated relative energies using density functional theory (DFT).

Exploiting single-electron transfer in Lewis pairs for catalytic bond-forming reactions

A single-electron transfer (SET) between tris(pentafluorophenyl)borane (B(C₆F₅)₃) and N,N-dialkylanilines is reported, which is operative via the formation of an electron donor–acceptor (EDA) complex involving π-orbital interactions as a key intermediate under dark conditions or visible-light irradiation depending on the structure of the aniline derivatives. This inherent SET in the Lewis pairs initiates the generation of the corresponding α-aminoalkyl radicals and their additions to electron-deficient olefins, revealing the ability of B(C₆F₅)₃ to act as an effective one-electron redox catalyst.

Radical–ion pair generation from common Lewis pairs and its application to catalytic carbon–carbon bond formation.

Protocol for Visible-Light-Promoted Desulfonylation Reactions Utilizing Catalytic Benzimidazolium Aryloxide Betaines and Stoichiometric Hydride Donor Reagents

An unprecedented photocatalytic system consisting of benzimidazolium aryloxide betaines (BI⁺-ArO^-) and stoichiometric hydride reducing reagents was developed for carrying out desulfonylation reactions of N-sulfonyl-indoles, -amides, and -amines, and α-sulfonyl ketones. Measurements of absorption spectra and cyclic voltammograms as well as density functional theory (DFT) calculations were carried out to gain mechanistic information. In the catalytic system, visible-light-activated benzimidazoline aryloxides (BIH-ArO^-), generated in situ by hydride reduction of the corresponding betaines BI⁺-ArO^-, donate both an electron and a hydrogen atom to the substrates. A modified protocol was also developed so that a catalytic quantity of more easily prepared hydroxyaryl benzimidazolines (BIH-ArOH) is used along with a stoichiometric hydride donor to promote the photochemical desulfonylation reactions.

1,2-Amino Alcohols via Cr/Photoredox Dual-Catalyzed Addition of α-Amino Carbanion Equivalents to Carbonyls

Herein, we report the synthesis of protected 1,2-amino alcohols starting from carbonyl compounds and α-silyl amines. The reaction is enabled by a Cr/photoredox dual catalytic system that allows the in situ generation of α-amino carbanion equivalents which act as nucleophiles. The unique nature of this reaction was demonstrated through the aminoalkylation of ketones and an acyl silane, classes of electrophiles that were previously unreactive toward addition of alkyl-Cr reagents. Overall, this reaction broadens the scope of Cr-mediated carbonyl alkylations and discloses an underexplored retrosynthetic strategy for the synthesis of 1,2-amino alcohols.

Electrophotocatalysis with a Trisaminocyclopropenium Radical Dication

Visible-light photocatalysis and electrocatalysis are two powerful strategies for the promotion of chemical reactions. Here, these two modalities are combined in an electrophotocatalytic oxidation platform. This chemistry employs a trisaminocyclopropenium (TAC) ion catalyst, which is electrochemically oxidized to form a cyclopropenium radical dication intermediate. The radical dication undergoes photoexcitation with visible light to produce an excited-state species with oxidizing power (3.33 V vs. SCE) sufficient to oxidize benzene and halogenated benzenes via single-electron transfer (SET), resulting in C-H/N-H coupling with azoles. A rationale for the strongly oxidizing behavior of the photoexcited species is provided, while the stability of the catalyst is rationalized by a particular conformation of the cis-2,6-dimethylpiperidine moieties.

Photoredox-Catalyzed Site-Selective α-C(sp3 )-H Alkylation of Primary Amine Derivatives

The synthetic utility of tertiary amines to oxidatively generate α-amino radicals is well established, however, primary amines remain challenging because of competitive side reactions. This report describes the site-selective α-functionalization of primary amine derivatives through the generation of α-amino radical intermediates. Employing visible-light photoredox catalysis, primary sulfonamides are coupled with electron-deficient alkenes to efficiently and mildly construct C-C bonds. Interestingly, a divergence between intermolecular hydrogen-atom transfer (HAT) catalysis and intramolecular [1,5] HAT was observed through precise manipulation of the protecting group. This dichotomy was leveraged to achieve excellent α/δ site-selectivity.

Photoaddition reactions of N-benzylglycinates containing α-trimethylsilyl group with dimethyl acetylenedicarboxylate: competitive formation of pyrroles vs. β-enamino esters

A study was conducted to gain insight into the preparative potential of photosensitized reactions of acyclic N-benzylglycinates containing an α-trimethylsilyl group with dimethyl acetylenedicarboxylate (DMAD). The photosensitizers employed in the reactions include 9,10-dicyanoanthracene (DCA), 1,4-dicyanonaphthalene (DCN), rose bengal (RB) and fullerene C60. The results show that photoirradiation of oxygenated solutions containing the photosensitizers, glycinates and dimethyl acetylenedicarboxylate leads to competitive formation of pyrroles and β-enamino-esters. The distributions of pyrrole and β-enamino-ester products formed in these reactions are highly influenced by the electronic nature of the phenyl ring substituent on the benzylglycinates and the photosensitizer used. These photoaddition reactions take place via mechanistic pathways involving competitive formation of azomethine ylides and secondary amines, generated by a mechanistic routes involving initial SET from the benzylglycinates to photosensitizers.

Photochemical Approach for the Preparation of N-Alkyl/Aryl Substituted Fulleropyrrolidines: Photoaddition Reactions of Silyl Group Containing α-Aminonitriles with Fullerene C60

The photochemical reactions of C₆₀ with N-(trimethylsilyl)methyl substituted and N-alkyl/aryl substituted α-aminonitriles were explored to evaluate the scope and reaction efficiency depending on the structural nature of amine substrates. The results showed that photoreactions of C₆₀ with trimethylsilyl group containing N-alkyl amines produced predominantly both trimethylsilyl and cyano group containing trans-pyrrolidine ring fused fulleropyrrolidines in a chemo- and stereoselective manner. Interestingly, photoreactions of C₆₀ with N-branched alkyl substituted amines led to exclusive formation of non-silyl containing cycloadducts. In contrast to those of N-alkyl substituted α-aminonitriles, photoreactions of N-(trimethylsilyl)methyl and N-aryl substituted α-aminonitriles gave rise to the formation of both trans- and cis-isomeric fulleropyrrolidines with an inefficient and non-stereoselective manner. The feasible mechanistic pathways leading to generation of fulleropyrrolidines are 1,3-dipolar cycloaddition of the azomethine ylides, generated by either a single electron transfer (SET) (under N₂-purged conditions) or H atom abstraction (under O₂-purged conditions) process, to fullerene C₆₀. The stereoselectivities of photoproducts depending on the nature of amines are likely to be associated with conformational stabilities of in situ generated azoemthine ylides.

Benzimidazolium Naphthoxide Betaine Is a Visible Light Promoted Organic Photoredox Catalyst

Benzimidazolium naphthoxide (^-ONap-BI⁺) was first synthesized and utilized as an unprecedented betaine photoredox catalyst. Photoexcited state of ^-ONap-BI⁺ generated by visible light irradiation catalyzes the reductive deiodination as well as desulfonylation reactions in which 1,3-dimethyl-2-phenylbenzimidazoline (Ph-BIH) cooperates with as an electron and hydrogen atom donor. Significant solvent effects on the reaction progress were discovered, and specific solvation toward imidazolium and naphthoxide moieties of ^-ONap-BI⁺ was proposed.

Enantioselective Synthesis of Pyrroloindolines via Noncovalent Stabilization of Indole Radical Cations and Applications to the Synthesis of Alkaloid Natural Products

While interest in the synthetic chemistry of radical cations continues to grow, controlling enantioselectivity in the reactions of these intermediates remains a challenge. Based on recent insights into the oxidation of tryptophan in enzymatic systems, we report a photocatalytic method for the generation of indole radical cations as hydrogen-bonded adducts with chiral phosphate anions. These noncovalent open-shell complexes can be intercepted by the stable nitroxyl radical TEMPO· to form alkoxyamine-substituted pyrroloindolines with high levels of enantioselectivity. Further elaboration of these optically enriched adducts can be achieved via a catalytic single-electron oxidation/mesolytic cleavage sequence to furnish transient carbocation intermediates that may be intercepted by a wide range of nucleophiles. Taken together, this two-step sequence provides a simple catalytic method to access a wide range of substituted pyrroloindolines in enantioenriched form via a standard experimental protocol from a common synthetic intermediate. The design, development, mechanistic study, and scope of this process are presented, as are applications of this method to the synthesis of several dimeric pyrroloindoline natural products.

An N-(acetoxy)phthalimide motif as a visible-light pro-photosensitizer in photoredox decarboxylative arylthiation

An efficient visible-light photoredox decarboxylative coupling of N-(acetoxy)phthalimides with aryl thiols has been developed. The reaction was performed well at room temperature with good tolerance of functional groups. Importantly, the visible-light photoredox decarboxylative arylthiation did not need an added photocatalyst.

Redox-Tag Processes: Intramolecular Electron Transfer and Its Broad Relationship to Redox Reactions in General

Explosive growth in the use of open shell reactivity, including neutral radicals and radical ions, in the field of synthetic organic chemistry has been observed in the past decade, particularly since the advent of ruthenium complexes in 2008. These complexes generally induce single-electron transfer (SET) processes via visible-light absorption. Additionally, recent significant advancements in organic electrochemistry involving SET processes to provide open shell reactivity offer a complementary method to traditional polarity-driven reactions described by two-electron transfer processes. In this Review, we highlight the importance of intramolecular SET processes in the field of synthetic organic chemistry, which seem to be more elusive than the intermolecular versions, since they are net redox-neutral and thus cannot simply be regarded as oxidations or reductions. Such intramolecular SET processes can rationally be understood in combination with concomitant bond formations and/or cleavages, and are regulated by a structural motif that we call a "redox tag." In order to describe modern radical-driven reactions involving SET processes, we focus on a classical formalism in which electrons are treated as particles rather than waves, which offers a practical yet powerful approach to explain and/or predict synthetic outcomes.

Lewis Acid Induced Toggle from Ir(II) to Ir(IV) Pathways in Photocatalytic Reactions: Synthesis of Thiomorpholines and Thiazepanes from Aldehydes and SLAP Reagents

Redox neutral photocatalytic transformations often require careful pairing of the substrates and photoredox catalysts in order to achieve a catalytic cycle. This can limit the range of viable transformations, as we recently observed in attempting to extend the scope of the photocatalytic synthesis of N-heterocycles using silicon amine protocol (SLAP) reagents to include starting materials that require higher oxidation potentials. We now report that the inclusion of Lewis acids in photocatalytic reactions of organosilanes allows access to a distinct reaction pathway featuring an Ir(III)*/Ir(IV) couple instead of the previously employed Ir(III)*/Ir(II) pathway, enabling the transformation of aromatic and aliphatic aldehydes to thiomorpholines and thiazepanes. The role of the Lewis acid in accepting an electron-either directly or via coordination to an imine-can be extended to other classes of photocatalysts and transformations, including oxidative cyclizations. The combination of light induced reactions and Lewis acids therefore promises access to new pathways and transformations that are not viable using the photocatalysts alone.

Single electron transfer promoted photoaddition reactions of α-trimethylsilyl substituted secondary N-alkylamines with fullerene C60

Single electron transfer (SET) promoted photoaddition reactions of secondary N-α-trimethylsilyl-N-alkylamines to C₆₀ were explored to gain a deeper understanding of the mechanistic pathways followed and to expand the library of novel types of organofullerenes that can be generated using this approach. The results show that photoreactions of 10% EtOH-toluene solutions containing C₆₀ and N-α-trimethylsilyl-N-alkylamines produce either aminomethyl-1,2-dihydrofullerenes or symmetric fulleropyrrolidines as major products depending on the nature of alkyl substituents. In contrast, photoreactions of 10% EtOH-ODCB solutions of these amines with C₆₀ mainly lead to the formation of symmetric fulleropyrrolidines. Based on the analysis of product distributions and the results of earlier studies, two feasible mechanistic pathways are proposed for these processes. One route is initiated by SET from the amine substrates to the triplet-excited state of C₆₀ to form the corresponding aminium radicals and C₆₀ anion radicals. EtOH-promoted desilylation of the aminium radicals then takes place to produce aminomethyl radicals which can either add to C₆₀ or couple with the C₆₀ radical anions to form respective radicals or anion precursors of aminomethyl-1,2-dihydrofullerene products. The competing pathway leading to the generation of symmetric fulleropyrrolidines also involves the formation of aminomethyl radicals by using the sequential SET-desilylation process. In this route, the aminomethyl radicals are oxidized by SET to C₆₀ to form iminium ions, which are then transformed to azomethine ylides by a pathway involving a second molecule of the secondary amine. Dipolar cycloaddition of the azomethine ylides to C₆₀ forms the symmetric fulleropyrrolidine cycloadducts. Importantly, the observation that symmetric fulleropyrrolidines are the sole products formed in photoreactions between N-α-trimethylsilyl-N-alkylamines and C₆₀ in 10% EtOH-ODCB has synthetic significance.

Synthetic Utilization of α-Aminoalkyl Radicals and Related Species in Visible Light Photoredox Catalysis

Single electron oxidation of amines provides an efficient way to access synthetically useful α-aminoalkyl radicals as reactive intermediates. After the single electron oxidation of amines, fragmentation of the resulting radical cations proceeds to give the α-aminoalkyl radicals along with generation of a proton. In the synthetic utilization of the α-aminoalkyl radicals, precise control of single electron transfer is essential, because further oxidation of the α-aminoalkyl radicals occurs more easily than the starting amines and the α-aminoalkyl radicals are converted into the corresponding iminium ions. As a result, photoinduced single electron transfer is quite attractive in the synthetic utilization of the α-aminoalkyl radicals. Recently, visible light-photoredox catalysis using transition metal-polypyridyl complexes and other dyes as catalysts has attracted considerable attention, where useful molecular transformations can be achieved through the single electron transfer process between the excited catalysts and substrates. In this context, MacMillan et al. ( Science 2011, 334 , 1114 , DOI: 10.1126/science.1213920 ) reported an aromatic substitution reaction of cyanoarenes with amines, where α-aminoalkyl radicals work as key reactive intermediates. Pandey and Reiser et al. ( Org. Lett. 2012 , 14 , 672 , DOI: 10.1021/ol202857t ) and our group ( Nishibayashi et al. J. Am. Chem. Soc. 2012 , 134 , 3338 , DOI: 10.1021/ja211770y ) independently reported reactions of amines with α,β-unsaturated carbonyl compounds, where addition of α-aminoalkyl radicals to alkenes is a key step. After these earliest examples, nowadays, a variety of transformations using the α-aminoalkyl radicals as reactive intermediates have been reported by many groups. The α-aminoalkyl radicals are usually produced from amines by single electron oxidation and the subsequent deprotonation of the C-H bond adjacent to the nitrogen atom. In addition, the α-aminoalkyl radicals are also produced from α-silylamines and α-amino acids in high efficiency through desilylation or decarboxylation after the single electron oxidation. The generated α-aminoalkyl radicals are utilized in a variety of reaction systems. In fact, reactions based on the addition of α-aminoalkyl radicals to alkenes and other unsaturated bonds have been extensively studied. Aromatic and other types of substitution reactions have also been investigated. Some of these transformations are achieved by combination of photoredox catalysts and other catalysts such as Brønsted and Lewis acids, organocatalysts, and transition metal catalysts. It is also noteworthy that the enantioselective reactions have been accomplished by combination of photoredox catalysts and chiral catalysts. The strategy for the generation of α-aminoalkyl radicals can be applied to utilize other types of alkyl radicals. In the generation of α-aminoalkyl radicals, the bond dissociation of the radical cations occurs at the α-position of amines. In relation to this process, synthetic utilization of other types of alkyl radicals generated by the bond dissociation of the radical cations at a remote position has been also investigated. These alkyl radicals have been applied to molecular transformations in a manner similar to the α-aminoalkyl radicals. Recently, organic synthesis using the α-aminoalkyl radicals and related alkyl radicals has been studied extensively. In this Account, we describe recent advances in photoredox-catalyzed synthetic utilization of these alkyl radicals.

Catalytic Carbocation Generation Enabled by the Mesolytic Cleavage of Alkoxyamine Radical Cations

A new catalytic method is described to access carbocation intermediates via the mesolytic cleavage of alkoxyamine radical cations. In this process, electron transfer between an excited state oxidant and a TEMPO-derived alkoxyamine substrate gives rise to a radical cation with a remarkably weak C-O bond. Spontaneous scission results in the formation of the stable nitroxyl radical TEMPO(.) as well as a reactive carbocation intermediate that can be intercepted by a wide range of nucleophiles. Notably, this process occurs under neutral conditions and at comparatively mild potentials, enabling catalytic cation generation in the presence of both acid sensitive and easily oxidized nucleophilic partners.