The selective functionalization of remote C–H bonds via intramolecular hydrogen atom transfer (HAT) is transformative for organic synthesis. This radical-mediated strategy provides access to novel reactivity that is complementary to closed-shell pathways. As modern methods for mild generation of radicals are continually developed, inherent selectivity paradigms of HAT mechanisms offer unparalleled opportunities for developing new strategies for C–H functionalization. This review outlines the history, recent advances, and mechanistic underpinnings of intramolecular HAT as a guide to addressing ongoing challenges in this arena. 1 Introduction 2 Nitrogen-Centered Radicals 2.1 sp3 N-Radical Initiation 2.2 sp2 N-Radical Initiation 3 Oxygen-Centered Radicals 3.1 Carbonyl Diradical Initiation 3.2 Alkoxy Radical Initiation 3.3 Non-alkoxy Radical Initiation 4 Carbon-Centered Radicals 4.1 sp2 C-Radical Initiation 4.2 sp3 C-Radical Initiation 5 Conclusion 
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                            C–H functionalization reactions enabled by hydrogen atom transfer to carbon-centered radicals
                        
                    
    
            Selective functionalization of ubiquitous unactivated C–H bonds is a continuous quest for synthetic organic chemists. In addition to transition metal catalysis, which typically operates under a two-electron manifold, a recent renaissance in the radical approach relying on the hydrogen atom transfer (HAT) process has led to tremendous growth in the area. Despite several challenges, protocols proceeding via HAT are highly sought after as they allow for relatively easy activation of inert C–H bonds under mild conditions leading to a broader scope and higher functional group tolerance and sometimes complementary reactivity over methods relying on traditional transition metal catalysis. A number of methods operating via heteroatom-based HAT have been extensively reported over the past few years, while methods employing more challenging carbon analogues have been less explored. Recent developments of mild methodologies for generation of various carbon-centered radical species enabled their utilization in the HAT process, which, in turn, led to the development of remote C(sp 3 )–H functionalization reactions of alcohols, amines, amides and related compounds. This review covers mostly recent advances in C–H functionalization reactions involving the HAT step to carbon-centered radicals. 
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                            - Award ID(s):
- 1955663
- PAR ID:
- 10273986
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 11
- Issue:
- 48
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 12974 to 12993
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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