Visible-light induced trifluoromethylation/cyclization cascade to access CF₃-containing pyrazolones by EDA complex

Area of Science:

• Organic Chemistry
• Medicinal Chemistry
• Synthetic Chemistry

Background:

• Trifluoromethyl groups enhance heterocycle bioactivity.
• Efficient synthesis of trifluoromethylated heterocycles is in high demand.
• Existing methods may lack efficiency or sustainability.

Purpose of the Study:

• Develop a novel, visible-light-driven, metal-free synthesis for trifluoromethylated pyrazolones.
• Establish an efficient radical addition/cyclization cascade strategy.
• Provide a sustainable route to functionalized heterocycles.

Main Methods:

• Visible-light irradiation (390-400 nm) initiates the reaction.
• An electron donor-acceptor (EDA) complex between Togni's reagent II and DABCO generates CF3 radicals.
• Metal-free conditions are employed, eliminating the need for external photocatalysts.

Main Results:

• A wide range of N-methacryloylhydrazones were converted to trifluoromethylated pyrazolones.
• Good to excellent yields were achieved for the target products.
• The reaction demonstrated high functional group tolerance.

Conclusions:

• A novel, efficient, and sustainable method for synthesizing trifluoromethylated pyrazolones was developed.
• The metal-free, visible-light-driven approach is operationally simple and scalable.
• This strategy provides a valuable route to diverse functionalized heterocycles.