Intramolecular nucleophilic capture of radical cations by tethered hydroxy functions

Organic Photoredox Catalysis

“…142 Thus, for reactions whose efficiencies suffer from BET, the triplet state of the photoredox catalyst may be the most important excited state. 144,145 undergoing PET primarily and with high efficiency, 146 while the substrate is oxidized to the cation radical in a secondary ET with the biphenyl cation radical (Ph−Ph• + ). The mechanism for these transformations is proposed to involve single electron oxidation of the silyl enol ether substrate (6.1), followed by cyclization to furnish distonic cation radical 6.9.…”

“…It is frequently the case with the neutral cyanoarenes that efficiency of PET suffers from BET, typically occurring before solvation of the contact radical [ion] pair. To combat BET, an appropriate mediator of ET is often included to improve cage escape; biphenyl (Ph−Ph) is commonly employed for this purpose,144,145 undergoing PET primarily and with high efficiency,146 while the substrate is oxidized to the cation radical in a secondary ET with the biphenyl cation radical (Ph−Ph• + ). Net Oxidative Transformations Involving Cyanoarene Photooxidants.…”

Aqueous Oxidation of Sulfonamide Antibiotics: Aromatic Nucleophilic Substitution of an Aniline Radical Cation

“…Previous work has shown that in the gas phase and in organic solvents,a romatic nucleophilic substitutions occur at aromatic rings that area ctivated by single-electron oxidation. [13][14][15][16] For oxidized dimethylaniline,s ubstitution in the para position can occur with variousn ucleophiles in acetonitrile (Scheme 1b). [14] However, we are unaware of reportso fs imilar reactionsi na queouss olution,o ro fs imilar reactions involving anilines which are not N-substituted.…”

“…Our working‐hypothesis was that the first step of oxidative transformation of sulfonamide drugs is a single‐electron transfer (SET) to an environmental oxidant, and that the resulting radical is a p ‐substituted aniline radical cation. Previous work has shown that in the gas phase and in organic solvents, aromatic nucleophilic substitutions occur at aromatic rings that are activated by single‐electron oxidation 13–16. For oxidized dimethylaniline, substitution in the para position can occur with various nucleophiles in acetonitrile (Scheme ) 14.…”

Reaction mechanisms : Part (i) Radical and radical ion reactions

“…90 For radical cations, incorporation of a pendant nucleophile can lead to cyclization via a polar process, as is illustrated by recent results reported by Crich 91 and Roth (Scheme 27). 92 The example cited in Scheme 27 also provides a good example of how a series of sequential rearrangements can be used as a tool for organic synthesis.…”