Substrate-Controlled Divergent Reductive Cyclization of 2-Arylanilines Using CO₂ as a Switching Reagent.

Area of Science:

• Organic synthesis
• Green chemistry
• Catalysis

Background:

• Carbon dioxide (CO2) capture and utilization are critical challenges in sustainable chemistry.
• Developing efficient methods for dual CO2 conversion remains an underdeveloped area.
• Quinoxaline derivatives are important scaffolds in medicinal chemistry and materials science.

Purpose of the Study:

• To develop a novel reductive cyclization strategy utilizing dual CO2 as a difunctional reagent.
• To explore the chemoselective conversion of mono-CO2 with related substrates.
• To elucidate the reaction mechanism and identify key intermediates.

Main Methods:

• Reductive cyclization of 2-indolylanilines with CO2 in the presence of poly(methylhydrosiloxane) (PMHS).
• Chemoselective cyclization of 2-pyrrolylanilines with mono-CO2.
• Mechanistic studies involving intermediate identification.

Main Results:

• Successful synthesis of methyl-substituted quinoxalines via dual CO2 reductive cyclization.
• Achieved chemoselective mono-CO2 conversion with 2-pyrrolylanilines.
• Identified N-diacylative intermediates as crucial for substrate-controlled divergence.

Conclusions:

• A novel and efficient method for dual CO2 utilization in organic synthesis has been established.
• The developed methodology offers a pathway to valuable quinoxaline derivatives.
• Substrate-controlled divergence in CO2 conversion is governed by intermediate formation.