Palladium-catalyzed intramolecular C(sp(3))--H functionalization: catalyst development and synthetic applications

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Intramolecular C-H functionalization is a key transformation in organic synthesis.
• Developing efficient and selective catalytic systems for C-H activation remains a significant challenge.
• Palladium catalysis offers versatile routes for C-H functionalization but often requires harsh conditions.

Purpose of the Study:

• To design a novel catalytic system for intramolecular C-H functionalization of alkane segments.
• To achieve regioselective synthesis of olefins and complex polycyclic molecules under mild conditions.
• To elucidate the mechanism of the proposed catalytic system.

Main Methods:

• Screening of phosphine ligands, including tris(5-fluoro-2-methylphenyl)phosphane (F-TOTP), with palladium acetate.
• Optimization of reaction conditions for intramolecular C-H functionalization.
• Mechanistic studies involving oxidative addition and cyclopalladation, proposing a six-membered palladium(II) palladacycle intermediate.

Main Results:

• The palladium/F-TOTP system demonstrated optimal metal-bonding properties for the reaction.
• Regioselective synthesis of olefins adjacent to quaternary benzylic carbon atoms was achieved.
• Novel bi- and tricyclic molecules were synthesized, showcasing the system's versatility.
• Application in the synthesis of verapamil and an analogue, followed by ruthenium-catalyzed hydroamidation.

Conclusions:

• A novel and efficient palladium-based catalytic system for intramolecular C-H functionalization has been developed.
• The system operates under mild conditions, offering high regioselectivity and broad applicability.
• The proposed mechanism involving a palladium(II) palladacycle provides insight into the reaction pathway.