Recent Advances in Reactions of Heteroatom-Centered Radicals

Abstract

Heteroatom-centered radicals show versatile reactivity and offer useful synthetic methods in organic chemistry. The development of new approaches for forming heteroatom-centered radicals has recently expanded the practicality of radical chemistry for synthesis. This review focuses on recent advances in reactions of representative heteroatom-centered radicals.1 Introduction2 Group 17 Elements: Chlorine and Bromine Radicals3 Group 15 and Group 16 Elements3.1 Nitrogen- and Oxygen-Centered Radicals3.2 Phosphorus- and Sulfur-Centered Radicals3.3 Other Radicals4 Group 14 Elements: Silicon-Centered Radicals5 Group 13 Elements: Boron-Centered Radicals6 Conclusion

Photogenerated Neutral Nitrogen Radical Catalyzed Bifunctionalization of Alkenes

“…Recently, the MacMillan group has revealed that thiyls, generated in situ from thiols by visible light photoredox catalysis, could serve as a general type of hydrogen‐atom‐transfer (HAT) catalysts to selectively activate benzylic ether C−H bonds . Despite these ground‐breaking contributions, other types of heteroatom‐centered radical catalysts remain largely unexplored …”

Addition of Heteroatom Radicals to endo-Glycals †

“…The reaction of phosphorus-centered radicals is well-established and has many synthetic applications, summarized in several reviews [28,51,52]. Because phosphorus can exist in different oxidation states, it is possible to generate phosphinyl, phosphinoyl, or phosphonyl radicals.…”

“…Sulfur-centered radicals can be easily generated from thiols by chemical or photochemical processes, because the S-H bond is much weaker than the corresponding O-H bond [28]. Subsequent addition to alkenes can initiate efficient chain reactions by hydrogen atom abstraction (thiol-ene reaction) or polymerizations.…”

“…During the last 25 years, we developed C-C bond formations by the addition of electrophilic radicals, mainly derived from malonates, to glycals 2 with various further synthetic transformations [24][25][26][27]. However, the addition of heteroatom radicals to glycals is very attractive as well, since such radicals exhibit the required electrophilic character [22,28]. On the other hand, heteroatom radicals are prone to undergo H atom abstraction, which is problematic in carbohydrate chemistry with various functional groups.…”

Radical‐Mediated Formal C(sp2)–H Functionalization of Aldehyde‐Derived N,N‐Dialkylhydrazones

“…The recent development of new strategies for generating heteroatom‐centered radicals has greatly expanded the practicality of radical chemistry for carbon–heteroatom bond formation . New methods for C(sp 2 )–H functionalization of hydrazones are expected to benefit from these advances.…”