Bio-inspired Cu(II) amido-quinoline complexes as catalysts for aromatic C-H bond hydroxylation
Monika1, Aniruddha Sarkar2, Naiwrit Karmodak1
1Department of Chemistry, Shiv Nadar IoE, U.P. 201314, India. basabbijayi@gmail.com.
Dalton Transactions (Cambridge, England : 2003)
|December 20, 2022
Summary
Copper complexes catalyze aromatic C-H hydroxylation with high selectivity for phenols using hydrogen peroxide. The non-radical pathway involves a key copper-oxygen intermediate, offering efficient catalytic activity.
Area of Science:
- * Inorganic Chemistry
- * Catalysis
- * Organic Synthesis
Background:
- * Aromatic C-H hydroxylation is a crucial transformation in organic synthesis.
- * Developing efficient and selective catalysts for C-H functionalization remains a significant challenge.
- * Copper complexes offer tunable electronic and steric properties for catalytic applications.
Purpose of the Study:
- * To synthesize and characterize novel copper(II) complexes with tetradentate amido-quinoline ligands.
- * To investigate the catalytic activity of these complexes in aromatic C-H hydroxylation.
- * To elucidate the reaction mechanism, including the role of the oxidant and the active species.
Main Methods:
- * Synthesis and characterization of copper(II) complexes (L1 & L2).
- * Catalytic testing for aromatic C-H hydroxylation using hydrogen peroxide (H₂O₂).
- * Mechanistic studies involving kinetic isotope effect (KIE), spectroscopic analyses, and density functional theory (DFT) calculations.
Main Results:
- * Successful synthesis and characterization of Cu(II) complexes with amido-quinoline ligands.
- * High selectivity (~90%) for phenol products achieved via a non-radical pathway.
- * Demonstrated high catalytic efficiency with a turnover number (TON) ≥720.
- * Mechanistic studies confirmed the involvement of a Cu(II)-OOH species.
Conclusions:
- * Tetradentate amido-quinoline ligands effectively support copper(II) catalysts for C-H hydroxylation.
- * The catalytic system operates via a non-radical pathway with high selectivity and efficiency.
- * The Cu(II)-OOH intermediate plays a critical role in the hydroxylation mechanism.
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