Copper-Catalyzed Regiodivergent Internal Allylic Alkylations

Area of Science:

• Organic Chemistry
• Catalysis
• Organometallic Chemistry

Background:

• Allylic alkylation is a fundamental transformation in organic synthesis.
• Controlling regioselectivity and stereospecificity in allylic alkylation remains a challenge, especially with internal substrates.
• Functionalized Grignard reagents offer versatile nucleophiles for carbon-carbon bond formation.

Purpose of the Study:

• To develop a copper-catalyzed method for the regioselective and stereospecific alkylation of unbiased internal allylic carbonates.
• To explore the preparation of a broad range of functionalized alkyl and aryl products.
• To elucidate the mechanistic origins of regioselectivity using computational methods.

Main Methods:

• Copper-catalyzed reaction of internal allylic carbonates with alkyl and aryl Grignard reagents.
• Employing two distinct catalytic conditions to access different reaction pathways (S_N2 and S_N2').
• Utilizing Density Functional Theory (DFT) calculations to investigate reaction mechanisms.

Main Results:

• Achieved high regioselectivity and stereospecificity in the alkylation of internal allylic carbonates.
• Demonstrated the ability to selectively form either S_N2 or S_N2' products based on catalytic conditions.
• Synthesized a diverse array of functionalized alkyl and aryl substituted alkenes with high E-alkene selectivity.
• DFT calculations revealed that the regioselectivity is governed by the distinct behaviors of homo- and heterocuprates.

Conclusions:

• The developed copper-catalyzed system provides a powerful and selective method for allylic alkylation.
• The methodology enables access to valuable E-alkene products with predictable stereochemical outcomes.
• Understanding the mechanistic role of cuprates offers insights for further catalyst design and reaction optimization.