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Aliphatic C-H Functionalization Using Pyridine N-Oxides as H-Atom Abstraction Agents
Marcel Schlegel1, Siran Qian1, David A Nicewicz1
1Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States.
This study demonstrates visible-light-mediated alkylation and heteroarylation of unactivated C(sp3)-H bonds using acridinium catalysts and pyridine N-oxides. The method efficiently functionalizes diverse aliphatic and heteroaromatic compounds via oxygen-centered radical intermediates.
Area of Science:
- Organic Chemistry
- Photocatalysis
- C-H Functionalization
Background:
- C(sp3)-H bond functionalization remains a significant challenge in organic synthesis.
- Developing catalytic methods for direct C-H activation under mild conditions is highly desirable.
Purpose of the Study:
- To develop a novel method for the alkylation and heteroarylation of unactivated C(sp3)-H bonds.
- To utilize visible light photocatalysis for efficient C-H functionalization.
Main Methods:
- Employing an acridinium photoredox catalyst.
- Using pyridine N-oxides as hydrogen atom transfer (HAT) precursors.
- Irradiation with visible light.
Main Results:
- Successful alkylation and heteroarylation of tertiary, secondary, and primary C(sp3)-H bonds.
- Generation of oxygen-centered radicals as key intermediates.
- Broad substrate scope, including diverse aliphatic C-H bonds and heteroarenes.
Conclusions:
- The developed method provides an efficient route for C(sp3)-H functionalization.
- The use of pyridine N-oxides offers tunable reactivity through structural modifications.
- This photocatalytic approach broadens the scope of C-H activation strategies.
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