Electrocatalytic Atom Transfer Radical Addition with Turbocharged Organocopper(II) Complexes

Area of Science:

• Catalysis
• Electrochemistry
• Organic Chemistry

Background:

• Copper-catalyzed halogen atom transfer is crucial for controlled radical polymerization and addition reactions.
• Electrochemistry offers a method to tune copper catalyst (Cu) reactivity between active (Cu^I) and dormant (Cu^II) states.

Purpose of the Study:

• To investigate the use of a macrocyclic pyridinophane ligand (L1) in electrochemically modulated copper-catalyzed halogen atom transfer.
• To explore the formation and reactivity of a novel copper-ligand complex for enhanced atom transfer radical addition.

Main Methods:

• Utilized a macrocyclic pyridinophane ligand (L1) with Cu^I to generate ^•CH₂CN radicals from BrCH₂CN.
• Employed electrochemistry to form and study the [Cu^II(L1)(CH₂CN)]⁺ complex.
• Applied electrochemical methods and simulations to quantify rate acceleration.
• Demonstrated the application in a copper-catalyzed bulk electrosynthesis for atom transfer radical addition.

Main Results:

• The [Cu^I(L1)]⁺ complex releases ^•CH₂CN radicals.
• A new species, [Cu^II(L1)(CH₂CN)]⁺, was formed in situ and exhibited a 1000-fold increase in halogen atom transfer reactivity upon reduction.
• This accelerated reactivity was confirmed by electrochemistry and simulation.
• The enhanced catalyst was successfully used in atom transfer radical addition reactions with styrenes.

Conclusions:

• Electrochemistry provides a powerful tool to modulate copper catalyst activity for halogen atom transfer.
• The *in situ* formation of the [Cu^II(L1)(CH₂CN)]⁺ complex offers a "turbocharged" catalyst with significantly enhanced reactivity.
• This approach presents a novel methodology for copper-catalyzed organic synthesis, particularly in electrosynthesis.