Regio-controllable [2+2] benzannulation with two adjacent C(sp³)-H bonds

Area of Science:

• Organic Chemistry
• Medicinal Chemistry
• Catalysis

Background:

• Traditional cycloaddition reactions often lack regiocontrol.
• Benzocyclobutene (BCB) scaffolds are increasingly important in medicinal chemistry.
• There is a need for selective synthetic routes to functionalized carbocycles.

Purpose of the Study:

• To develop a regioselective synthesis of benzocyclobutene (BCB) scaffolds.
• To explore a novel palladium-catalyzed double C-H activation strategy.
• To generate diverse C(sp3)-rich carbocyclic structures.

Main Methods:

• Palladium-catalyzed double C-H activation of adjacent methylene units in carboxylic acids.
• Utilized bidentate amide-pyridone ligands for enhanced selectivity.
• Employed a formal [2+2] cycloaddition mechanism involving C-H and aryl-halogen bonds.

Main Results:

• Achieved regioselective synthesis of functionalized benzocyclobutenes (BCBs) and hetero-BCBs.
• Demonstrated compatibility with a wide range of cyclic and acyclic aliphatic acids.
• Showcased applicability with various dihaloheteroarenes.

Conclusions:

• The developed method offers a selective and controllable route to BCB scaffolds.
• This approach provides access to valuable carbocyclic structures found in pharmaceuticals and natural products.
• Highlights the utility of palladium catalysis in C-H activation for complex molecule synthesis.