Identification of Ti(salen) Complexes for Efficient Catalysis in Single-Electron Steps by Cyclic Voltammetry

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Titanium complexes are widely used in catalysis.
• Radical arylation of epoxides is a key transformation in organic synthesis.
• Developing more efficient and sustainable catalytic systems is crucial.

Purpose of the Study:

• To identify an active titanium(salen) catalyst for radical arylation of epoxides.
• To understand the mechanism-based predictors for catalytic success.
• To compare the new catalyst with existing titanocene systems.

Main Methods:

• Cyclic voltammetry studies to determine redox potentials and E_qC_r-equilibria.
• Synthesis and characterization of titanium(salen) complexes with varying ligand backbones.
• Evaluation of catalytic activity in the radical arylation of epoxides.

Main Results:

• An active Ti(salen) catalyst featuring a tetrasubstituted ligand backbone was identified.
• The tetrasubstituted ligand reduces chloride binding to Ti(III), enhancing substrate binding and activity.
• Catalysis is efficient in ethyl acetate and can be initiated electrochemically or with base metals.
• The new catalyst system offers milder conditions, broader substrate scope, and tunable properties compared to titanocene catalysis.

Conclusions:

• The developed Ti(salen) catalyst represents a significant advancement in radical arylation of epoxides.
• This catalyst enables more sustainable and versatile synthetic routes.
• The findings provide a foundation for designing next-generation titanium-based catalysts.