Eosin Y as a Redox Catalyst and Photosensitizer for Sequential Benzylic C−H Amination and Oxidation

Abstract

A new synergistic multicatalytic activation mode of eosin Y has been discovered by exploiting the redox potential of its ground state and excited state. This catalytic strategy proves to be an enabling tool for visible-light-driven sequential benzylic C-H amination and oxidation of o-benzyl-N-methoxyl-benzamides when using Selectfluor as a hydrogen atom transfer (HAT) reagent and O as oxidant. Efficient synthesis of a range of diversely functionalized 3-hydroxyisoindolinones can thus be achieved with good yields and selectivity at mild reaction conditions. Preliminary mechanistic studies and DFT calculations suggest that eosin Y works as a redox catalyst and photosensitizer.

Visible‐Light‐Induced C2 Alkylation of Heterocyclic N‐Oxides with N‐Hydroxyphthalimide Esters under Metal‐Free Conditions

“…Likely, the Cs 2 CO 3 coordination effect could promote the formation of alkyl radicals. [27] Based on literature precedents [21,[25][26][27][28] and experimental observations, a plausible mechanism is proposed (Scheme 5). Initially, the photocatalyst Eosin Y transfers to an excited state EY* under blue light irradiation.…”

Oxidative Fluorination of Cyclopropylamides through Organic Photoredox Catalysis

“…[20] By comparing the reduction potentials of cyclopropylamide 1 a, Selectfluor, and tripletstate benzophenone (BP 3* ), neither Selectfluor (E 1/2 red = + 0.33 V) [21,22] nor triplet-state benzophenone (E 1/2 BP*=BP À = + 1.27 V) [23] are able to oxidize cyclopropylamide 1 a (measured E 1/2 red =+ 1.67 V). However, Selectfluor or the Selectfluor-derived radical cation (I, E 1/2 red =+ 0.79 V) [24] could…”

Testing the limits of radical-anionic CH-amination: a 10-million-fold decrease in basicity opens a new path to hydroxyisoindolinesviaa mixed C–N/C–O-forming cascade

“…We will show how this structural modication diverts the cascade towards incorporation of a late C-O bond forming step 17 and opens a synthetic route to 3-hydroxyisoindolinones. Recently, Xiao et al 18 independently developed a mechanistically different version of 3-hydroxyisoindolinone synthesis from secondary amides (Scheme 3c). An interesting feature of Xiao's work is that the same catalyst is used in two different ways to promote the two cascade stages.…”