Multisite Proton-Coupled Electron Transfer Enables Iodanyl Radical Catalysis.

Area of Science:

• Organic Chemistry
• Catalysis
• Electrochemistry

Background:

• Hypervalent iodine reagents typically involve two-electron redox processes (I(I), I(III), I(V)).
• Previous work suggested iodanyl radicals (I(I)/I(II) cycle) in C-H/N-H coupling, bypassing I(III) intermediates.

Purpose of the Study:

• To investigate the role of iodanyl radicals in N-H activation and C-N coupling.
• To explore one-electron redox pathways in hypervalent iodine catalysis.
• To develop novel catalysts for metal-free electrocatalytic C-N bond formation.

Main Methods:

• Combined experimental and computational investigation.
• Electrochemical generation of iodanyl radicals.
• Mechanistic studies involving multisite proton-coupled electron transfer (MS-PCET).

Main Results:

• Anodically generated iodanyl radicals directly promote C-H/N-H coupling via MS-PCET.
• The iodanyl radical acts as an electron acceptor, and carboxylate additives act as proton acceptors.
• Developed two new catalysts (4c, 4d) with tailored redox properties, expanding reaction scope.

Conclusions:

• Iodanyl radicals can directly activate substrates without I(III) intermediacy.
• Systematic tuning of iodanyl radical redox properties allows rational catalyst design.
• One-electron hypervalent iodine mechanisms offer complementary synthetic routes and new catalyst design principles for metal-free electrocatalysis.