Multifunctional Ligands for Enhanced Catalysis

Introduction

Transition metal-catalyzed C-H functionalization replaces an inert carbon-hydrogen bond with a functional group, expediently altering the properties of the parent molecule to access new classes of compounds. Although C-H functionalization represents a green chemistry approach as it precludes the need for pre-functionalized starting materials, there are still two main sustainability shortcomings with most current methodologies.

Challenges in C-H Functionalization

Selectivity of Functionalization

The first challenge is achieving functionalization of specific C-H bonds without affecting other C-H sites in the molecule. A widely employed strategy to control the selectivity of metal-catalyzed C-H bond functionalization reactions has relied upon the covalent attachment of directing groups (i.e., pyridine, oxime, diazo) to the parent molecule.

The requisite installation and removal of directing groups make the overall transformation less appealing from an atom- and step-economy perspective.

Use of Precious Metals

The second challenge is to substitute commonly used precious transition metals with more benign earth-abundant alternatives.

Proposed Research Program

The proposed research program will address these shortcomings by developing an innovative and more efficient way for selective metal-catalyzed functionalization of aromatic and aliphatic C-H bonds without pre-attaching a directing group.

Innovative Strategies

The proposed strategies will rely on the design of multifunctional ligands capable of simultaneous binding to the substrate and the transition metal catalyst. The proposed approach will take advantage of the ability of Cr(0) to form a π-arene complex and activate the aromatic and benzylic C-H bonds.

Potential Impact

Addressing these challenges associated with C-H activation technology would have the power to unlock many industrial applications, such as:

• Valorizing fine chemicals
• Modifying complex natural products
• Developing drug leads
• Enhancing polymers