Issue 37, 2020
From the journal:

Chemical Science

Synthesis of pentasubstituted 2-aryl pyrroles from boryl and stannyl alkynes via one-pot sequential Ti-catalyzed [2 + 2 + 1] pyrrole synthesis/cross coupling reactions†

Yukun Cheng, ORCID logo a   Channing K. Klein ORCID logo a  and  Ian A. Tonks ORCID logo *a  

* Corresponding authors

a Department of Chemistry, University of Minnesota – Twin Cities, 207 Pleasant St SE, Minneapolis, Minnesota 55455, USA
E-mail: itonks@umn.edu

Abstract

Multisubstituted pyrroles are commonly found in many bioactive small molecule scaffolds, yet the synthesis of highly-substituted pyrrole cores remains challenging. Herein, we report an efficient catalytic synthesis of 2-heteroatom-substituted (9-BBN or SnR3) pyrroles via Ti-catalyzed [2 + 2 + 1] heterocoupling of heteroatom-substituted alkynes. In particular, the 9-BBN-alkyne coupling reactions were found to be very sensitive to Lewis basic ligands in the reaction: exchange of pyridine ligands from Ti to B inhibited catalysis, as evidenced by in situ11B NMR studies. The resulting 2-boryl substituted pyrroles can then be used in Suzuki reactions in a one-pot sequential fashion, resulting in pentasubstituted 2-aryl pyrroles that are inaccessible via previous [2 + 2 + 1] heterocoupling strategies. This reaction provides a complementary approach to previous [2 + 2 + 1] heterocouplings of TMS-substituted alkynes, which could be further functionalized via electrophilic aromatic substitution.

Graphical abstract: Synthesis of pentasubstituted 2-aryl pyrroles from boryl and stannyl alkynes via one-pot sequential Ti-catalyzed [2 + 2 + 1] pyrrole synthesis/cross coupling reactions

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Article information

DOI
https://doi.org/10.1039/D0SC01576H
Article type
Edge Article
Submitted
16 Mar 2020
Accepted
06 Sep 2020
First published
08 Sep 2020
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2020,11, 10236-10242

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Synthesis of pentasubstituted 2-aryl pyrroles from boryl and stannyl alkynes via one-pot sequential Ti-catalyzed [2 + 2 + 1] pyrrole synthesis/cross coupling reactions

Y. Cheng, C. K. Klein and I. A. Tonks, Chem. Sci., 2020, 11, 10236 DOI: 10.1039/D0SC01576H

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