A visible light mediated alkyl sulfonylative cascade using Hantzsch esters via SO₂ insertion

Area of Science:

• Organic Chemistry
• Photocatalysis
• Synthetic Methodology

Background:

• Cyclization reactions are crucial for constructing complex organic molecules.
• Visible light photocatalysis offers a sustainable approach to organic synthesis.
• Sulfonylation reactions are important for introducing sulfur-containing functional groups.

Purpose of the Study:

• To develop a novel visible light-mediated cascade cyclization reaction.
• To achieve alkyl sulfonylative cyclization of alkynyl cyclohexadienones.
• To synthesize diverse dihydrochromenone derivatives efficiently.

Main Methods:

• Visible light irradiation.
• Organophotocatalysis using 4-CzIPN.
• Utilizing alkyl Hantzsch esters as alkyl source.
• Employing DABSO as a sulfur dioxide (SO2) source.
• Cascade reaction involving SO2 insertion and cyclization.

Main Results:

• Successful synthesis of various dihydrochromenone derivatives.
• Good product yields achieved under mild conditions.
• Demonstration of an energy-efficient synthetic protocol.
• Identification of alkyl Hantzsch esters and DABSO as effective reagents.
• Mechanism probed through fluorescence quenching and control experiments.

Conclusions:

• The developed protocol provides an efficient route to dihydrochromenones.
• Visible light photocatalysis enables a sustainable and mild synthetic strategy.
• The reaction mechanism involves SO2 insertion and cascade cyclization.