A Modular Cascade Synthetic Strategy Toward Structurally Constrained Boron-Doped Polycyclic Aromatic Hydrocarbons

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Structurally constrained boron-doped polycyclic aromatic hydrocarbons (sc-B-PAHs) are challenging to synthesize.
• Existing methods often lack efficiency and broad applicability for complex PAH structures.

Purpose of the Study:

• To develop a novel synthetic strategy for constructing difficult-to-access sc-B-PAHs.
• To explore the synthesis of B-doped and BN-doped [4]helicenes and double [4]helicenes.
• To investigate the structural, photophysical, and electrochemical properties of the synthesized compounds.

Main Methods:

• A cascade reaction involving borylative cyclization, boron migration, and electrophilic borylation.
• Utilized readily available ortho-aryl-substituted diarylalkynes as starting materials.
• Characterization of synthesized sc-B-PAHs using X-ray crystallography, spectroscopy (UV/Vis, fluorescence), and cyclic voltammetry.

Main Results:

• Successfully synthesized various B-doped and BN-doped [4]helicenes and double [4]helicenes.
• Demonstrated broad substrate scope (18 examples) with versatile functional group tolerance.
• Observed unique supramolecular structures, including alternating π-stacked dimers and 2D lamellar π-stacking in BN-doped derivatives.

Conclusions:

• The developed cascade reaction is a powerful tool for the rapid generation of novel sc-B-PAHs.
• The synthesized sc-B-PAHs exhibit good stability and interesting structural motifs.
• These findings are valuable for structure-property relationship studies and potential optoelectronic applications.