Ionic and covalent copper(II)-based catalysts for Michael additions. The mechanism

Area of Science:

• Organometallic Chemistry
• Organic Synthesis
• Catalysis

Background:

• Michael addition reactions are fundamental carbon-carbon bond-forming processes in organic chemistry.
• Developing efficient catalysts for Michael additions in neutral media is crucial for sustainable synthesis.
• Copper complexes have shown promise as catalysts in various organic transformations.

Purpose of the Study:

• To investigate the catalytic activity of Cu(SbF6)2-AdamBox and copper(II) bis-(5-tert-butylsalicylaldehydate) in Michael addition reactions.
• To elucidate the reaction mechanism and identify the active nucleophilic species.
• To explore the use of these copper complexes as catalysts in neutral media.

Main Methods:

• Spectroscopic techniques including UV-vis and IR spectroscopy were employed.
• Electrospray ionization mass spectrometry (ESI-MS) was utilized for mechanistic studies.
• Catalytic reactions were performed under neutral reaction conditions.

Main Results:

• Both Cu(SbF6)2-AdamBox and copper(II) bis-(5-tert-butylsalicylaldehydate) effectively catalyzed the Michael addition.
• Mechanistic investigations provided evidence for the formation of copper enolates.
• These copper enolates of beta-dicarbonyl compounds were identified as the active nucleophilic species.

Conclusions:

• Cu(SbF6)2-AdamBox and copper(II) bis-(5-tert-butylsalicylaldehydate) are efficient catalysts for Michael additions in neutral media.
• The reaction proceeds via copper enolate intermediates.
• This study contributes to the understanding of copper-catalyzed Michael additions and the development of novel catalytic systems.