Intermolecular Heck Coupling with Hindered Alkenes Directed by Potassium Carboxylates

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Traditional palladium-catalyzed Mizoroki-Heck reactions show limited effectiveness with sterically hindered, unbiased alkenes.
• Intermolecular reactions involving all-carbon tetrasubstituted alkenes remain largely unexplored.

Purpose of the Study:

• To develop a novel palladium-catalyzed method for the arylation of sterically demanding tri- and tetrasubstituted olefins.
• To enable the formation of quaternary carbon centers, particularly at Fsp3-hybridized ring junctions.

Main Methods:

• Utilizing palladium(0) catalysis in conjunction with bulky monophosphine ligands.
• Employing pendant carboxylic acids as directing groups to guide the arylation process.
• Developing a strategy for the subsequent removal of the carboxylate directing group.

Main Results:

• Successfully achieved the arylation of tri- and tetrasubstituted olefins, which were previously unreactive.
• Established quaternary carbons at high Fsp3-attached-ring junctures with high efficiency.
• Demonstrated that the carboxylate directing group prevents over-arylation, allowing for further functionalization.

Conclusions:

• The developed method expands the scope of palladium-catalyzed Heck reactions to include challenging alkene substrates.
• This approach provides a versatile route for synthesizing complex organic molecules with quaternary stereocenters.
• The ability to remove the directing group offers flexibility for subsequent synthetic transformations.