From C-H to C-N Bonds: Three Challenges, Three Catalysts, Three Solutions

Area of Science:

• Organic Chemistry
• Catalysis
• Medicinal Chemistry

Background:

• N-heterocycles are crucial structural motifs in numerous pharmaceutical agents.
• Intramolecular C-H amination offers an efficient and sustainable synthetic route to N-heterocycles.
• Developing robust and active iron-based catalysts is essential for advancing this methodology.

Purpose of the Study:

• To address key challenges in iron-catalyzed intramolecular C-H amination: catalyst accessibility, mechanistic insight, and catalyst performance.
• To introduce and evaluate novel iron catalysts for C-H amination reactions.
• To enhance the scope and efficiency of synthesizing N-heterocyclic compounds.

Main Methods:

• Utilized commercially available iron(II) iodide (FeI2) for initial catalytic studies.
• Employed bis(hexamethyldisilazide)iron(II) [Fe(HMDS)2] to conduct detailed mechanistic investigations.
• Developed and tested iron catalysts featuring mesoionic carbene ligands for enhanced activity and substrate scope.

Main Results:

• FeI2 demonstrated good activity but was limited to substrates with activated C-H bonds.
• Mechanistic studies with Fe(HMDS)2 elucidated key intermediates in the C-H amination pathway.
• Iron catalysts with mesoionic carbene ligands exhibited unprecedented activity, enabling the amination of diverse C-H bonds.

Conclusions:

• The study presents a multi-faceted approach to advancing iron-catalyzed intramolecular C-H amination.
• Different iron catalysts were developed to overcome specific limitations in accessibility, mechanistic understanding, and catalytic efficiency.
• The findings provide a foundation for the development of more robust and versatile iron catalysts for sustainable N-heterocycle synthesis in drug discovery.