Benzylic Ligand Hydroxylation Starting from a Dicopper μ‐η²:η² Peroxo Intermediate: Dramatic Acceleration of the Reaction by Hydrogen‐Atom Donors

Abstract

Radicals in directed pathways: The μ‐η2:η2 peroxo CuII2 intermediate 1 shows a much faster benzylic ligand hydroxylation than systems without phenol. This novel reactivity can be further accelerated by addition of external H‐atom donors such as TEMPO‐H. The results imply initial H‐atom transfer leading to the formation of phenoxyl radicals. A highly reactive copper oxyl intermediate is then formed, which inserts oxygen into the benzylic CH bond.

Melanosome-Targeting Near-Infrared Fluorescent Probe with Large Stokes Shift for in Situ Quantification of Tyrosinase Activity and Assessing Drug Effects on Differently Invasive Melanoma Cells

“…The material was prepared according to the reported literature. 35 Synthesis of N-1. To a solution of 2-hydroxy-1naphthaldehyde (2.07 g, 12 mmol) in anhydrous DMF (20 mL), Cs 2 CO 3 (3.91 g, 12 mmol) was added with stirring under a N 2 atmosphere.…”

Scrutinizing the Noninnocence of Quinone Ligands in Ruthenium Complexes: Insights from Structural, Electronic, Energy, and Effective Oxidation State Analyses

“…For a long time, redox noninnocence of ligands was considered a rare spectroscopic curiosity, a uniquely electronic phenomenon, but over the past decades its critical role in enzymatic transformations was evidenced. − For example, in the active form of the active site of galactose oxidase enzyme, , an extra electron is added to the tyrosine ligand bound to the Cu II center when facilitating the overall two-electron oxidation of alcohols to aldehydes . The great potential in this cooperative mechanism has mostly been recognized in the ongoing intense efforts to achieve sustainable chemical energy conversion covering fields of inert molecule activation, artificial photosynthesis, multielectron reactivity, etc. − Conceptually it is the most intuitive strategy of cooperative catalysis: use redox-noninnocent ligands as electron reservoirs for metals that cannot store enough electrons for the required multielectron transformations.…”

Monooxygenation of an appended phenol in a model system of tyrosinase: implications on the enzymatic reaction mechanism

“…calc. for C 19 Bis(2-pyridylmethyl)benzylamine (L H ). The known synthesis for L H has been modified.…”

“…These systems either hydroxylate external monophenolic substrates [12][13][14][15][16][17] or are able to hydroxylate an aromatic part of the ligand framework. [18][19][20][21][22][23] One of the first model systems of the latter type has been published by Karlin and coworkers in 1984. 23 Their Cu 2 XYL system is based on a binuclear copper(I) complex with a m-xylene bridged ligand providing six nitrogen donor atoms.…”