Photoinduced Palladium Catalysis Enables Dynamic Kinetic Asymmetric Allylic Imidation

Area of Science:

• Organic Chemistry
• Catalysis
• Asymmetric Synthesis

Background:

• Palladium-catalyzed dynamic kinetic asymmetric transformation (DYKAT) is crucial for synthesizing enantiomerically enriched molecules.
• Existing DYKAT methods face challenges with unsymmetrical 1,3-disubstituted allylic substrates.

Purpose of the Study:

• To develop a general and efficient method for the DYKAT of unsymmetrical 1,3-disubstituted allylic electrophiles.
• To achieve high regio- and enantioselectivity in the synthesis of chiral allylic amines and amino alcohols.

Main Methods:

• Photoinduced palladium-catalyzed dynamic kinetic asymmetric transformation (DYKAT).
• Utilized unsymmetrical 1,3-disubstituted allylic electrophiles such as allyl esters, vinyl epoxides, and vinyl carbonates.
• Investigated reaction mechanisms using mechanistic studies.

Main Results:

• Achieved highly regio- and enantioselective imidation of unsymmetrical allylic electrophiles.
• Delivered chiral allylamines and amino alcohols with regioselectivity ratios up to >20:1 and enantiomeric excess up to 99%.
• Identified a visible-light-promoted interconversion of diastereomeric π-allyl Pd(II) intermediates via a Pd species/allyl radical equilibrium.

Conclusions:

• The developed photoinduced Pd-catalyzed DYKAT offers a powerful and general solution for challenging allylic substrates.
• The method provides mild and efficient access to valuable chiral allylic amines and amino alcohols.
• Mechanistic insights highlight the role of visible-light excitation and radical intermediates in enantioconvergent synthesis.