Intermolecular Double C-H Annulation via 1,4-Pd Migration: A Modular Strategy for Heteropolycycle Construction

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Palladium-catalyzed reactions are crucial for C-H functionalization.
• Constructing complex heteropolycycles remains a challenge in organic synthesis.

Purpose of the Study:

• To develop a novel intermolecular double C-H annulation strategy.
• To synthesize diverse heteropolycyclic compounds using readily available starting materials.

Main Methods:

• The study utilizes a 1,4-palladium (Pd) migration mechanism.
• It involves a cascade sequence including Heck cyclization, Pd migration, double alkyne insertion, and C-H activation.

Main Results:

• The reaction successfully couples alkene-tethered aryl halides with 1,n-diynes.
• Structurally diverse tetracyclic and hexacyclic heteropolycycles were synthesized.
• The method demonstrated broad substrate scope and excellent regioselectivity.

Conclusions:

• A novel and efficient palladium-catalyzed intermolecular double C-H annulation has been established.
• This methodology provides a powerful tool for constructing complex heteropolycycles.
• The reaction's broad scope and selectivity make it valuable for synthetic chemists.