Visible-Light-Driven Photocatalytic Cascade Multioxidation: A Route to α-Sulfinylphthalides

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Direct C(sp3)-H functionalization and tandem reactions are key strategies for synthesizing complex molecules.
• Developing efficient synthetic routes from basic feedstocks to high-value fine chemicals remains a significant challenge in organic chemistry.

Purpose of the Study:

• To develop an efficient synthetic pathway for the olefinic difunctionalization of o-methylstyrenes.
• To achieve oxidative dehydrogenative lactonization catalyzed by LaBr3 under visible light irradiation.
• To synthesize a diverse range of alpha-sulfinylphthalides.

Main Methods:

• Direct C(sp3)-H functionalization of o-methylstyrenes with thiophenols.
• Tandem reaction sequence involving oxidative dehydrogenative lactonization.
• Visible light photocatalysis facilitated by LaBr3.
• Mild reaction conditions under an oxygen atmosphere.

Main Results:

• Successful synthesis of a wide range of alpha-sulfinylphthalides.
• Moderate diastereoselectivity achieved in the product formation.
• Demonstration of the reaction's efficiency without additional photosensitizers or strong oxidants.
• Confirmation of LaBr3's crucial role through mechanistic studies.

Conclusions:

• The presented synthetic pathway offers an efficient route to alpha-sulfinylphthalides.
• The methodology utilizes mild conditions and visible light, avoiding harsh reagents.
• LaBr3 catalysis is essential for the successful tandem reaction sequence.