Ruthenium-Catalyzed Cross-Selective Asymmetric Oxidative Coupling of Arenols

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Oxidative cross-coupling reactions are crucial for forming carbon-carbon bonds.
• Achieving high chemo- and enantioselectivity in these reactions, especially with substrates of similar oxidation potentials, remains a challenge.
• Ruthenium-salen complexes have shown promise as catalysts in various organic transformations.

Purpose of the Study:

• To develop a catalytic system for chemo- and enantioselective oxidative cross-coupling of arenols.
• To investigate the selective synthesis of C1-symmetric bis(arenols) from substituted 2-naphthols and phenols.
• To understand the factors governing cross-selectivity in these coupling reactions.

Main Methods:

• Utilized a (aqua)ruthenium(salen) complex (1c) as the catalyst.
• Employed oxidative cross-coupling reactions involving substituted 2-naphthols and phenols.
• Analyzed reaction outcomes based on chemo- and enantioselectivity, and steric/electronic effects of substrates.

Main Results:

• Complex 1c demonstrated good to high chemo- and enantioselectivity in arenol oxidative cross-coupling.
• The catalytic system successfully produced C1-symmetric bis(arenols) from mixtures of C3- and C7-substituted 2-naphthols or phenols.
• Cross-selectivity was found to be primarily governed by steric effects of the arenols, overriding electronic differences.

Conclusions:

• The developed ruthenium(salen) catalytic system offers a unique and effective method for selective oxidative cross-coupling of arenols.
• Steric control is a key factor in achieving high cross-selectivity, enabling the synthesis of specific C1-symmetric bis(arenols).
• The findings provide valuable insights into catalyst design and reaction mechanism for selective C-C bond formation.