Alkene isomerization-hydroarylation tandem catalysis: Indole c2-alkylation with aryl-substituted alkenes leading to 1,1-diarylalkanes

Takeshi Yamakawa, Naohiko Yoshikai

Research output: Contribution to journalArticlepeer-review

53 Citations (Scopus)

Abstract

A cobalt-N-heterocyclic carbene catalyst generated from CoBr2, imidazolium salt, and cyclohexylmagnesium bromide was found to promote the imine-directed C2-alkylation of indoles with nonconjugated arylalkenes through a tandem alkene isomerization-hydroarylation process, affording 1,1-diarylalkanes with exclusive regioselectivity. The feasibility of the tandem catalysis was demonstrated for allyl-, homoallyl-, and bishomoallylbenzene derivatives. The catalytic system is also applicable to a variety of β-substituted styrene derivatives. Mechanistic experiments using deuterium-labeled indole substrate and Grignard reagent provided insight into the cobalt-mediated C -H activation step, which likely involves exchange of the C2-hydrogen atom of the former and the β-hydrogen atoms of the latter. ...? but thats secondary: A catalytic system consisting of CoBr2, N-heterocyclic carbene, and cyclohexylmagnesium bromide promotes the imine-directed addition of indoles to nonconjugated aryl-substituted alkenes through tandem alkene isomerization-hydroarylation, affording 1,1-diarylalkane derivatives with exclusive regioselectivity. Deuterium-labeling experiments revealed the involvement of the secondary alkyl Grignard reagent in the cobalt-mediated C -H activation process.

Original languageEnglish
Pages (from-to)1242-1246
Number of pages5
JournalChemistry - An Asian Journal
Volume9
Issue number5
DOIs
Publication statusPublished - 2014 May
Externally publishedYes

Keywords

  • alkenes
  • alkylation
  • C -H functionalization
  • cobalt
  • indoles

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry

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