1,6-Carbene transfer: gold-catalyzed oxidative diyne cyclizations

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Metal-catalyzed cyclization reactions are crucial in organic synthesis.
• Existing methods for synthesizing functionalized indenones often involve hazardous reagents like diazo compounds.
• Development of efficient and safer synthetic routes is an ongoing challenge.

Purpose of the Study:

• To develop a novel gold-catalyzed oxidative cyclization of diynes.
• To explore a new reaction cascade initiated by oxygen transfer from N-oxides.
• To synthesize highly substituted functionalized indenones via a carbene intermediate.

Main Methods:

• Utilizing a gold catalyst for the oxidative cyclization of diynes.
• Employing N-oxides as oxygen transfer agents.
• Investigating reaction mechanisms involving α-oxo carbene and vinyl carbene intermediates.

Main Results:

• An unprecedented oxidative cyclization of diynes was achieved using a gold catalyst.
• The reaction proceeds via an oxygen transfer from N-oxide to a gold-activated alkyne, forming an α-oxo carbene.
• Highly substituted functionalized indenones were synthesized through alkyl migration or sp(3)-CH insertion, potentially involving a 1,6-carbene shift.

Conclusions:

• The developed gold-catalyzed protocol offers an efficient and unprecedented route to functionalized indenones.
• This method provides a safer alternative to traditional syntheses relying on diazo compounds.
• The study expands the scope of gold catalysis in oxidative cyclization reactions.