Recent Advances in Benzannulation Approaches to Aromatic Frameworks.

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Catalysis

Background:

• Substituted arenes are crucial building blocks in pharmaceuticals, agrochemicals, and materials science.
• Conventional arene functionalization methods are often limited by the starting material's substitution pattern.

Purpose of the Study:

• To review recent advancements (last 5 years) in benzannulation strategies for synthesizing substituted arenes.
• To compare transition-metal-catalyzed and metal-free approaches for benzannulation.
• To provide guidance on selecting and designing benzannulation routes for complex arene synthesis.

Main Methods:

• Exploration of metal-catalyzed cascades (e.g., transition-metal catalysis).
• Investigation of metal-free cyclization processes (e.g., pericyclic reactions, radical cyclizations, benzyne chemistry).
• Comparative analysis of different benzannulation methodologies.

Main Results:

• Benzannulation enables the construction of aromatic cores from acyclic or nonaromatic precursors.
• Recent developments offer improved control over regioselectivity and functional-group tolerance.
• Both metal-catalyzed and metal-free strategies present distinct advantages in bond-forming logic and mechanism.

Conclusions:

• Benzannulation is a powerful strategy to access complex substituted arenes, overcoming limitations of traditional methods.
• Recent advances focus on step economy and sustainability in benzannulation route design.
• This review provides practical insights for synthetic chemists utilizing benzannulation.