Copper Hydride Catalyzed Reductive Claisen Rearrangements

Area of Science:

• Organic Chemistry
• Catalysis
• Reaction Mechanisms

Background:

• The Claisen rearrangement is a fundamental carbon-carbon bond-forming reaction in organic synthesis.
• Developing efficient and stereoselective variants remains a key challenge in synthetic chemistry.
• Copper-catalyzed reactions offer unique reactivity and selectivity profiles.

Purpose of the Study:

• To develop a novel reductive Claisen rearrangement protocol.
• To achieve high yields and diastereoselectivities in the rearrangement.
• To elucidate the reaction mechanism and identify key intermediates.

Main Methods:

• In situ generation of copper hydride catalyst.
• Use of diethoxymethylsilane as a stoichiometric reductant.
• Analysis of reaction products using NMR spectroscopy and chiral chromatography.
• Mechanistic investigations including kinetic studies and computational modeling.

Main Results:

• An efficient reductive Claisen rearrangement was successfully developed.
• Yields up to 95% with good to excellent diastereoselectivities were achieved.
• Mechanistic studies confirmed a stereospecific rearrangement via a chair transition state involving (E)-silyl ketene acetals as intermediates.

Conclusions:

• The developed method provides a powerful new tool for stereoselective synthesis.
• The reaction proceeds through a distinct mechanism involving silyl ketene acetals, differing from copper enolate pathways.
• This work expands the scope of copper-catalyzed rearrangements and offers insights into their mechanisms.