β-C-H bond functionalization of ketones and esters by cationic Pd complexes

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• C-H activation offers direct functionalization of organic molecules but often requires directing groups for efficiency.
• Existing methods enable C-H activation of various functional groups, but ketones and esters remain challenging substrates.
• Developing C-H activation reactions directed by native functional groups is crucial for broader synthetic applications.

Purpose of the Study:

• To develop an effective catalyst for C-H functionalization of ketones and carboxylic esters.
• To report diverse methyl β-C-H functionalizations of these substrates.
• To enable the synthesis of complex cyclic systems.

Main Methods:

• Utilized a monoprotected amino neutral amide (MPANA) ligand with palladium catalysis.
• Employed HBF₄ for in situ generation of cationic Pd(II) complexes.
• Investigated intermolecular arylation, hydroxylation, and intramolecular C(sp³)-H/C(sp²) coupling reactions.
• Conducted mechanistic experiments and density functional theory (DFT) studies.

Main Results:

• Achieved diverse methyl β-C-H functionalizations of ketones and carboxylic esters.
• Demonstrated compatibility with cyclic ketones and lactams, providing access to spirocyclic and fused ring systems.
• Identified cationic Pd(II) complexes with MPANA ligands as key to reactivity.

Conclusions:

• The developed catalytic system effectively functionalizes ketones and esters via C-H activation.
• The use of MPANA ligands and cationic Pd(II) complexes enhances catalyst-substrate interaction and C-H cleavage.
• This method provides a valuable tool for synthesizing complex organic molecules and cyclic structures.