Direct Cyclopropanation of α-Cyano β-Aryl Alkanes by Light-Mediated Single Electron Transfer Between Donor–Acceptor Pairs

Jing Li, Martin J. Lear, Yujiro Hayashi

Research output: Contribution to journalArticlepeer-review

Abstract

Cyclopropanes are traditionally prepared by the formal [2+1] addition of carbene or radical based C1 units to alkenes. In contrast, the one-pot intermolecular cyclopropanation of alkanes by redox active C1 units has remained unrealised. Herein, we achieved this process simply by exposing β-aryl propionitriles and C1 radical precursors (N-oxy esters) to base and blue light. The overall process is redox-neutral and a photocatalyst, whether metal- or organic-based, is not required. Our findings support that single electron transfer (SET) from the α-cyano carbanion of the propionitrile to the N-oxy ester is facilitated by blue-light via their electron donor–acceptor (EDA) complex. The α-cyano carbon radical thus formed can then lose a β-proton to form a π-resonance stabilised radical anion that preferentially couples at the benzylic β-position with a decarboxylated C1 radical unit. This new transition metal-free chemistry tolerates both electron rich and electron deficient (hetero)aryl systems, even sulfide or alkene functionality, to afford a range of cis-aryl/cyano cyclopropanes bearing congested tetrasubstituted quaternary carbons.

Original languageEnglish
Pages (from-to)5901-5905
Number of pages5
JournalChemistry - A European Journal
Volume27
Issue number19
DOIs
Publication statusPublished - 2021 Apr 1
Externally publishedYes

Keywords

  • alkane
  • cyclopropanation
  • decarboxylation
  • radical
  • single electron transfer

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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