Keteniminium ion-initiated cascade cationic polycyclization

Area of Science:

• Organic Chemistry
• Synthetic Chemistry

Background:

• Cationic polycyclization is a key strategy for synthesizing complex molecular architectures.
• Developing efficient methods for constructing polycyclic nitrogen heterocycles remains a significant challenge in organic synthesis.

Purpose of the Study:

• To report a novel and efficient keteniminium-initiated cationic polycyclization reaction.
• To demonstrate the utility of ynamides as versatile building blocks for complex molecule synthesis.

Main Methods:

• The study employed keteniminium intermediates generated in situ.
• Triflic acid or bistriflimide were used as promoters for the cationic polycyclization.
• Readily available ynamides served as starting materials.

Main Results:

• A straightforward and efficient synthesis of polycyclic nitrogen heterocycles was achieved.
• The reaction provides access to molecules with up to three contiguous stereocenters and seven fused cycles.
• Complex polycyclic structures were obtained in a single synthetic operation.

Conclusions:

• Keteniminium-initiated cationic polycyclization offers a powerful route to complex nitrogen heterocycles.
• Ynamides are highly effective precursors for multiple, consecutive cationic transformations.
• This methodology provides a streamlined approach to intricate polycyclic scaffolds.