External oxidant-compatible phosphorus(III)-directed site-selective C-H carbonylation

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• C-H functionalization is a key area in synthetic chemistry.
• Developing selective and efficient methods for indole functionalization remains a challenge.
• Phosphorus(III) directing groups offer unique reactivity patterns.

Purpose of the Study:

• To develop a novel external oxidant-compatible system for phosphorus(III)-directed C-H functionalization.
• To achieve efficient C-H esterification of indoles using carbon monoxide and alcohols.
• To explore the mechanism and scope of this new synthetic strategy.

Main Methods:

• Palladium catalysis with a phosphorus(III)-directing group.
• Utilizing benzoquinone as an external oxidant.
• C-H esterification of indoles with carbon monoxide and alcohols.

Main Results:

• An efficient C-H esterification of indoles with exclusive C7-selectivity was achieved.
• The strategy employs an easily accessible and removable directing group.
• Cheap carbonylation sources and a broad substrate scope were demonstrated.
• Two cyclopalladated intermediates were confirmed by X-ray analysis, revealing mechanistic insights.

Conclusions:

• A novel and efficient P(III)-directed C-H functionalization system has been developed.
• This method provides excellent C7-selectivity for indole esterification.
• The strategy offers practical advantages including accessible directing groups and cost-effective reagents.