Aromatic Metamorphosis: Skeletal Editing of Aromatic Rings.

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Materials Science

Background:

• Aromatic rings are core structures in numerous vital compounds, yet modifying their fundamental frameworks is challenging.
• Existing methods primarily focus on peripheral transformations, leaving core skeletal modifications underexplored.
• Novel strategies are needed to access diverse molecular architectures from common aromatic precursors.

Purpose of the Study:

• To introduce and demonstrate the concept of "aromatic metamorphosis" for skeletal transformations of aromatic rings.
• To develop efficient synthetic routes for novel molecular architectures with diverse element compositions.
• To showcase the application of aromatic metamorphosis in constructing molecular libraries for pharmaceuticals and materials science.

Main Methods:

• Stepwise conversion of dibenzothiophenes and dibenzofurans into triphenylenes using palladium and nickel catalysts.
• Oxidation to sulfones followed by nucleophilic aromatic substitution (S_NAr) reactions for constructing carbazoles, fluorenes, and heterohelicenes.
• Nickel-catalyzed boron insertion into benzofurans to form benzoxaborins, and manganese-catalyzed/lithium-promoted methods for diverse heterocycle synthesis.
• Reductive dilithiation of thiophenes for accessing nonbiogenic heteroles like boroles, phospholes, and siloles.

Main Results:

• Demonstrated stepwise conversion of dibenzothiophenes/dibenzofurans to triphenylenes via C-S/C-O bond activation.
• Developed efficient S_NAr-based routes to optoelectronic materials and a heterohelicene library.
• Achieved scalable synthesis of benzoxaborins via nickel-catalyzed boron insertion, highlighting practical utility.
• Expanded methods for diverse heterocycle synthesis through various catalytic and metal-promoted transformations.

Conclusions:

• Aromatic metamorphosis provides a powerful platform for skeletal modification of aromatic rings, enabling access to novel molecular scaffolds.
• This strategy significantly expands chemical space and facilitates the rapid construction of diverse molecular libraries.
• Aromatic metamorphosis offers new retrosynthetic disconnections and a paradigm shift in molecular design for pharmaceuticals and materials.