Enantioselective Contrathermodynamic Olefin Isomerization

Area of Science:

• Organic Chemistry
• Photochemistry
• Catalysis

Background:

• Contrathermodynamic positional isomerization of olefins is challenging.
• Enantioselective synthesis of olefins is crucial for pharmaceuticals and materials.

Purpose of the Study:

• To develop a light-driven method for enantioselective contrathermodynamic olefin isomerization.
• To achieve high regio- and enantioselectivity in olefin synthesis.

Main Methods:

• Excited-state electron transfer initiated reaction.
• Sequential oxidation and deprotonation of enol ethers.
• Utilizing a chiral chromium(II) cocatalyst with a bioxazoline (BiOX) ligand.
• Regio- and enantioselective protodemetalation using methanol.

Main Results:

• Successful enantioselective contrathermodynamic positional isomerization of olefins.
• Generation of an allylic radical intermediate captured by a chiral chromium complex.
• Production of terminal olefin products with up to 95:5 er.
• Identification of enantiodetermining protodemetalation and two primary kinetic isotope effects (KIEs).

Conclusions:

• The developed method offers a novel pathway for enantioselective olefin synthesis.
• The findings provide insights into the mechanism of enantioselective catalysis involving radical intermediates.
• This work expands the toolkit for asymmetric synthesis using photochemistry.