A comprehensive picture of the one-electron oxidation chemistry of enols, enolates and α-carbonyl radicals: oxidation potentials and characterization of radical intermediates

A Molybdenum(0) Isocyanide Analogue of Ru(2,2′‐Bipyridine)32+: A Strong Reductant for Photoredox Catalysis

“…Initially only the trans isomer of 1 is present . Electron transfer between photoexcited Mo(CNAr 3 NC) 3 and trans ‐ 1 produces radical intermediate A − , which can be oxidized to diradical B by Mo(CNAr 3 NC) 3 + in the electronic ground state . B can then either undergo intramolecular reaction to form product 2 or it can revert to substrate 1 , thereby producing a mixture of cis and trans isomers.…”

Electrochemistry of Tri‐substituted Porphyrins with β‐Appended Ethyl Acetoacetate and Acetylacetone in Neutral and Basic Nonaqueous Solvents

“…Additional evidence for deprotonation of the EAA‐ or acac‐appended β ‐substituents is given by the appearance of a new oxidation process at E pa =0.11 to 0.20 V in CH 2 Cl 2 solutions containing 0.1 M TBAOH (see Figure ) for CuTPP(EAA)Ph 2 and CuTPP(acac)Ph 2 . This process is assigned to an oxidation of the negatively charged EAA or acac substituents to give their radical forms on the basis of data in the literature for the oxidation of acetylacetonate (acac − ) and related molecules in nonaqueous media. The oxidation of acac − in CH 2 Cl 2 containing 0.1 M TBAOH is located at E pa =0.50 V (Figure a) while a more facile acac − oxidation of CuTPP(acac)Ph 2 occurs at 0.11 V (Figure c) for a scan rate of 0.1 V/s, thus suggesting a strong electron‐donating effect of the porphyrin unit on the deprotonated form of the acac substituent.…”

“…It should be noted that the neutral and deprotonated forms of the β ‐EAA or acac substituents in eq 1a and 1b are both electroactive in the absence of the porphyrin, the neutral form of acac being reduced by one electron at −2.0 to −2.2 V in CH 3 CN with the generation of hydrogen and the anionic form (acac − ) being oxidized by one electron at potentials close to 0.0 V vs SCE in CH 3 CN or CH 2 Cl 2 . Thus, an electrochemical characterization of MTPP(EAA − )X 2 and MTPP(acac − )X 2 should provide information on the interaction between the porphyrin π‐ring system and the negatively charged enolate substituent.…”

Photocatalytic α‐Oxyamination of Stable Enolates, Silyl Enol Ethers, and 2‐Oxoalkane Phosphonic Esters

“…Two equivalents of the stronger oxidizing agent tris(1,10-phenanthroline)iron(III) hexafluorophosphate {[Fe III (phen) 3 (PF 6 ) 3 ], E = +1.08 V vs. SCE} afforded α-carbonyl cations as a result of two subsequent one-electron oxidation steps. [13][14][15] The Jahn group reported the oxidation of ester enolates with CuCl 2 or ferrocenium ions and subsequent trapping of the α-ester radicals with 2,2,6,6-1 oxidation of TEMPO into the 2,2,6,6-tetramethylpiperidine-1-oxoammonium ion, which was nucleophilically attacked to yield α-functionalized carbonyl compounds. The reaction time was significantly reduced by the use of the microreactor flow technique.…”