Single-Electron-Transfer Strategy for Reductive Radical Cyclization: Fe(CO)₅ and Phenanthroline System

Area of Science:

• Organic Chemistry
• Organometallic Chemistry
• Radical Chemistry

Background:

• Electron transfer reactions are crucial for generating reactive intermediates.
• Low-valent iron complexes offer unique catalytic properties.
• Alkyl iodides are versatile precursors for radical generation.

Purpose of the Study:

• To develop a novel electron-transfer strategy for generating alkyl radicals.
• To synthesize cyclic compounds using iron-mediated radical reactions.
• To explore tandem reactions involving alkyl radicals.

Main Methods:

• Utilizing iron pentacarbonyl [Fe(CO)5] as a low-valent iron reductant.
• Employing 1,10-phenanthroline and diisopropylamine as additives.
• Investigating 5-exo cyclization reactions of in situ generated alkyl radicals.
• Performing tandem addition reactions with Michael acceptors.
• Conducting photophysical and electrochemical studies to elucidate the mechanism.

Main Results:

• Successful generation of alkyl radical species from alkyl iodides via electron transfer.
• Synthesis of diverse pyrrolidines, tetrahydrofurans, and carbocycles through 5-exo cyclization.
• Demonstration of tandem addition reactions with Michael acceptors.
• Elucidation of the reaction mechanism involving electron transfer from Fe(CO)5 to alkyl iodide.

Conclusions:

• The developed electron-transfer strategy provides an efficient route to alkyl radicals.
• This method facilitates the synthesis of various heterocyclic and carbocyclic compounds.
• The study offers insights into the mechanism of iron-mediated radical generation and cyclization.