A new highly asymmetric chelation-controlled heck arylation

Area of Science:

• Organic Chemistry
• Asymmetric Catalysis
• Synthetic Methodology

Background:

• Traditional methods for cyclic ketone functionalization often require strong bases or protecting groups.
• Achieving high enantioselectivity in alpha-alkylation of cyclic ketones remains a challenge.
• Direct coupling to ketone enolates can suffer from regioselectivity issues.

Purpose of the Study:

• To develop a novel, highly asymmetric chelation-controlled Heck arylation methodology.
• To enable the efficient synthesis of enantiomerically enriched 2-aryl-2-methyl cyclopentanones.
• To circumvent the limitations of existing methods, such as the need for strong bases or blocking groups.

Main Methods:

• Development of a new chelation-controlled Heck arylation reaction.
• Utilizing N-methyl pyrrolidin enol ethers as substrates.
• Optimization of reaction conditions for yield and enantioselectivity.

Main Results:

• Successful formation of 2-aryl-2-methyl cyclopentanones with good to very good two-step yields (45-78%).
• Achieved excellent chiral enrichment, with enantiomeric excess (ee) ranging from 90-98%.
• The method operates without requiring strong bases or blocking of alternative alpha-carbons.

Conclusions:

• The developed asymmetric Heck arylation is a powerful tool for synthesizing chiral cyclopentanones.
• A proposed chelated pi-intermediate effectively explains the high level of chiral induction observed.
• This methodology offers a more efficient and milder alternative to existing synthetic routes.