Weak Base-Promoted Direct Cross-Coupling of Naphthalene-1,8-diaminato-substituted Arylboron Compounds

Area of Science:

• Organic Chemistry
• Catalysis

Background:

• Suzuki-Miyaura coupling (SMC) typically requires strong bases, which can cause protodeborylation of organoboron reagents.
• Fluorine-substituted aryl and heteroaryl boron compounds are particularly susceptible to protodeborylation.

Purpose of the Study:

• To develop a direct SMC method using novel naphthalene-1,8-diaminato (dan)-substituted aryl boron compounds (Ar-B(dan)).
• To overcome the challenge of protodeborylation in SMC reactions.

Main Methods:

• Utilized naphthalene-1,8-diaminato (dan)-substituted aryl boron compounds (Ar-B(dan)) with diminished boron-Lewis acidity.
• Employed a weak base and a palladium/copper cooperative catalyst system for direct SMC.
• Investigated the stability of Ar-B(dan) reagents towards protodeborylation.

Main Results:

• Achieved direct SMC of Ar-B(dan) reagents with remarkable stability against protodeborylation.
• Enabled efficient incorporation of perfluoroaryl- and heteroaryl-B(dan) reagents with high functional group tolerance.
• Demonstrated sequential cross-coupling via chemoselective reactions of other metallic moieties, leading to protection-free synthesis of oligoarenes.

Conclusions:

• Developed a robust SMC strategy using Ar-B(dan) compounds that bypasses the need for strong bases and avoids protodeborylation.
• The B(dan) moiety's stability allows for controlled, sequential cross-coupling reactions, offering a streamlined route to complex molecules.