Diazaphospholene-Catalyzed Radical Reactions from Aryl Halides

Area of Science:

• Organic Chemistry
• Catalysis
• Radical Reactions

Background:

• Diazaphospholenes are established hydride transfer catalysts.
• Their application in radical reactions is an emerging field.
• Stoichiometric cyclizations of aryl iodides using diazaphospholene hydrides have been reported.

Purpose of the Study:

• To develop a catalytic method for radical cyclizations mediated by diazaphospholene hydrides.
• To expand the substrate scope to include aryl bromides.
• To explore intermolecular radical hydroarylations.

Main Methods:

• Catalytic regeneration of diazaphospholene hydrides using phenylsilane and alkali metal salts.
• Visible light irradiation for aryl bromide cyclizations.
• Synthesis and characterization of cyclized products.

Main Results:

• Successful catalytic radical cyclization of aryl iodides.
• Expanded scope to include aryl bromides, with visible light enhancement.
• Achieved a dearomative cyclization.
• Demonstrated six intermolecular radical hydroarylations with various arenes, thiophenes, and pyridine.

Conclusions:

• The developed method provides a catalytic route for diazaphospholene-hydride-mediated radical cyclizations.
• The methodology is versatile, accommodating diverse substrates and reaction types.
• This work broadens the synthetic utility of diazaphospholenes in radical chemistry.