Direct Photoinduced Heck-Type Cyclization of Aryl Halides toward Polycyclic Indoles

Area of Science:

• Organic Chemistry
• Photocatalysis
• Radical Chemistry

Background:

• Indole derivatives are crucial in pharmaceuticals and materials science.
• Efficient synthesis of 2-aryl indoles remains a challenge.
• Radical-mediated C-H functionalization offers a promising synthetic route.

Purpose of the Study:

• To develop a novel organo-photocatalytic method for synthesizing 2-aryl indoles.
• To utilize readily available phenothiazine and phenoxazine as photocatalysts.
• To achieve the synthesis under mild, room-temperature conditions.

Main Methods:

• Employing deprotonated phenothiazine and phenoxazine as potent reductants.
• Utilizing a radical process initiated by C-Cl bond cleavage.
• Characterizing the catalysts' reducing ability (up to -3.41 V vs SCE) and light-absorbing properties.

Main Results:

• Successful synthesis of 2-aryl indoles via an organo-photocatalytic pathway.
• Demonstration of the catalysts' high reducing power in the excited state.
• Confirmation of mild reaction conditions (room temperature).

Conclusions:

• Phenothiazine and phenoxazine are effective organo-photocatalysts for 2-aryl indole synthesis.
• The developed method offers a mild and efficient route for indole functionalization.
• This approach expands the toolkit for radical-mediated organic synthesis.