Lithium-Mediated Mechanochemical Cyclodehydrogenation.

Area of Science:

• Organic Synthesis
• Materials Chemistry
• Nanotechnology

Background:

• Cyclodehydrogenation is crucial for synthesizing polycyclic aromatic hydrocarbons (PAHs), heteroaromatic compounds, and nanographenes.
• Anionic cyclodehydrogenation using potassium(0) is effective for creating rylene structures but suffers from poor practicality, pyrophoricity, and scalability.
• Existing methods present significant challenges for widespread synthetic application.

Purpose of the Study:

• To develop a novel, practical, and scalable method for anionic cyclodehydrogenation.
• To establish a user-friendly protocol for synthesizing PAHs and nanographenes.
• To synthesize novel nanographenes, including the longest nonsubstituted molecular rylene.

Main Methods:

• Development of a lithium(0)-mediated mechanochemical anionic cyclodehydrogenation reaction.
• Utilizing conventional lithium(0) wire at room temperature and under air.
• Investigating reaction scope, mechanism, and gram-scale synthesis via computational and NMR analyses.

Main Results:

• Achieved efficient synthesis of perylene from 1,1'-binaphthyl in 30 min with 94% yield.
• Demonstrated the reaction's practicality, air tolerance, and room-temperature operation.
• Successfully synthesized novel nanographenes through multiple cyclodehydrogenations, including quinterrylene ([5]rylene).

Conclusions:

• The lithium(0)-mediated mechanochemical protocol offers significant advantages in practicality and applicability over existing methods.
• This user-friendly approach enables the synthesis of complex nanographenes, expanding synthetic capabilities.
• The study provides a comprehensive understanding of the reaction's scope, mechanism, and limitations, paving the way for future applications.