Iron-Catalyzed Photoinduced LMCT: A 1° C–H Abstraction Enables Skeletal Rearrangements and C(sp3)–H Alkylation

Herein we disclose an iron-catalyzed method to access skeletal rearrangement reactions akin to the Dowd–Beckwith ring expansion from unactivated C­(sp3)–H bonds. Photoinduced ligand-to-metal charge transfer at the iron center generates a chlorine radical, which abstracts electron-rich C­(sp3)–H bond...

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Bibliographic Details
Published inACS catalysis Vol. 11; no. 12; pp. 7442 - 7449
Main Authors Kang, Yi Cheng, Treacy, Sean M, Rovis, Tomislav
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 18.06.2021
Subjects
LMCT
iron catalysis
skeletal rearrangement
Dowd−Beckwith
photocatalysis
primary C(sp3)−H alkylation
primary C(sp3)-H alkylation
Dowd-Beckwith
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Summary:Herein we disclose an iron-catalyzed method to access skeletal rearrangement reactions akin to the Dowd–Beckwith ring expansion from unactivated C­(sp3)–H bonds. Photoinduced ligand-to-metal charge transfer at the iron center generates a chlorine radical, which abstracts electron-rich C­(sp3)–H bonds. The resulting unstable alkyl radicals can undergo rearrangement in the presence of suitable functionality. Addition to an electron deficient olefin, recombination with a photoreduced iron complex, and subsequent protodemetalation allow for redox-neutral alkylation of the resulting radical. Simple adjustments to the reaction conditions enable the selective synthesis of the directly alkylated or the rearranged-alkylated products. As a radical clock, these rearrangements also enable the measurement of rate constants of addition into various electron deficient olefins in the Giese reaction.
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ISSN:2155-5435
2155-5435
DOI:10.1021/acscatal.1c02285