Borylation Directed Borylation of Indoles Using Pyrazabole Electrophiles: A One-Pot Route to C7-Borylated-Indolines

Jürgen Pahl, Emily Noone, Marina Uzelac, Kang Yuan, Michael J. Ingleson

Research output: Contribution to journalArticlepeer-review

14 Citations (SciVal)

Abstract

Pyrazabole (1) is a readily accessible diboron compound that can be transformed into ditopic electrophiles. In 1 (and derivatives), the B⋅⋅⋅B separation is ca. 3 Å, appropriate for one boron centre bonding to N and one to the C7 of indoles and indolines. This suitable B⋅⋅⋅B separation enables double E−H (E=N/C) functionalisation of indoles and indolines. Specifically, the activation of 1 with HNTf2 generates an electrophile that transforms N−H indoles and indolines into N/C7-diborylated indolines, with N−H borylation directing subsequent C7−H borylation. Indole reduction to indoline occurs before C−H borylation and our studies indicate this proceeds via hydroboration—C3-protodeboronation to produce an intermediate that then undergoes C7 borylation. The borylated products can be converted in situ into C7-BPin-N-H-indolines. Overall, this represents a transient directed C−H borylation to form useful C7-BPin-indolines.

Original languageEnglish
Article numbere202206230
JournalAngewandte Chemie - International Edition
Volume61
Issue number32
DOIs
Publication statusPublished - 8 Aug 2022

Bibliographical note

Funding Information:
This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No 769599). We acknowledge SIRCAMS at University of Edinburgh for performing mass spectrometry and Dr. G. Nichol for collecting X‐ray diffraction data for . 2 [30]

Data Availability Statement
The data that support the findings of this study are available in the Supporting Information of this article

Keywords

  • Boranes
  • C−H Borylation
  • Electrophilic Substitution
  • Indoles
  • Transient Directing Group

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry

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