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

J. Pahl, E. Noone, M. Uzelac, K. Yuan, Michael Ingleson

Research output: Contribution to journalArticlepeer-review

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 HNTf 2 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
JournalAngewandte Chemie International Edition
Early online date10 Jun 2022
DOIs
Publication statusE-pub ahead of print - 10 Jun 2022

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