Decarboxylative alkylation of alkenes

Area of Science:

• Synthetic Organic Chemistry
• Catalysis
• Functional Group Transformations

Background:

• Alkenes are crucial building blocks in synthesizing polymers, agrochemicals, and pharmaceuticals.
• Traditional alkene functionalization primarily involves addition reactions, limiting direct substitution and alkylation strategies.
• Existing methods for alkene alkylation, such as cross-metathesis, have limitations in scope, diastereoselectivity, and substrate compatibility.

Purpose of the Study:

• To develop a novel method for the direct C-H alkylation of alkenes.
• To enable the synthesis of complex substituted alkenes that are difficult to access via current methodologies.
• To utilize readily available carboxylic acids as a versatile source of alkyl groups.

Main Methods:

• A polar decarboxylative alkylation strategy was developed, deviating from radical-based approaches.
• Persistent alkylzinc intermediates were generated from redox-active esters.
• Palladium-catalyzed cross-coupling of alkylzinc species with alkenyl thianthrenium salts was employed.

Main Results:

• The method achieves regio- and diastereoselective C-H alkylation of a wide range of alkenes, including cyclic, acyclic, terminal, internal, mono-, di-, and tri-substituted types.
• Carboxylic acids serve as diverse and accessible alkylating agents.
• High diastereoselectivity was observed in the formation of substituted alkenes.

Conclusions:

• This work introduces a powerful new transformation for alkene functionalization.
• The developed method expands the synthetic chemist's toolbox for constructing complex molecules containing substituted alkenes.
• The approach offers a versatile and efficient route to diverse alkylated alkenes from readily available starting materials.