Reductive samarium (electro)catalysis enabled by Sm^III-alkoxide protonolysis.

Area of Science:

• Organometallic Chemistry
• Catalysis
• Synthetic Organic Chemistry

Background:

• Samarium diiodide (SmI₂) is a potent single-electron reductant widely used in organic synthesis.
• Catalytic turnover of SmI₂ is hindered by the difficulty in cleaving strong samarium(III)-oxygen bonds.
• Previous methods using reactive oxophiles complicate catalyst speciation and limit synthetic scope.

Purpose of the Study:

• To develop generalizable methods for catalytic turnover using samarium diiodide.
• To enable efficient samarium-catalyzed reductive cross-coupling reactions.
• To overcome limitations associated with strong Sm^III-O bond cleavage in catalytic cycles.

Main Methods:

• A mild and selective protonolysis strategy was employed to facilitate catalyst turnover.
• The method involves the intermolecular reductive cross-coupling of ketones and acrylates.
• Control over selectivity was achieved by tuning solvent, pK_a, and the samarium coordination sphere.

Main Results:

• Successful demonstration of samarium-catalyzed, intermolecular reductive cross-coupling with broad substrate scope.
• The protonolysis strategy effectively addresses the challenge of cleaving strong Sm^III-O bonds.
• Modularity of the approach allows for rational control of reaction selectivity.

Conclusions:

• A novel and generalizable catalytic system for samarium diiodide has been established.
• The developed protonolysis strategy offers a mild and selective route for reductive cross-coupling.
• This work lays the foundation for future advancements in catalytic and electrocatalytic lanthanide chemistry.