Borane catalysed annulative sulfenylation of internal alkynes: towards the synthesis and study of fused heterocycles

Das, Sampurna, Pramanik, Milan, Westphäling, Johannes, Gupta, Abhishek Kumar, Wirth, Thomas ORCID: https://orcid.org/0000-0002-8990-0667, Buurma, Niklaas J. ORCID: https://orcid.org/0000-0003-0260-5057, Zysman-Colman, Eli, Baik, Mu-Hyun and Melen, Rebecca L. ORCID: https://orcid.org/0000-0003-3142-2831 2026. Borane catalysed annulative sulfenylation of internal alkynes: towards the synthesis and study of fused heterocycles. Chemical Science 17 (23) , pp. 11682-11692. 10.1039/d6sc01123c

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Abstract

Herein, we disclose a B(C6F5)3-catalysed intramolecular cyclisation reaction of N-protected alkynyl anilines and phenols to generate 5-membered heterocycles, including 3-sulfenyl indoles (17 examples, up to 91% yield) and benzo[b]furans (9 examples, up to 90% yield), in good yields with several functional group tolerances. This protocol was adapted into an annulative π-extension (APEX) reaction when using diyne derivatives of aniline and phenol, which effectively led to sulfenylated polyaromatic heterocycles, such as benzo[a]carbazole or naphtho[1,2-b]benzofurans. These products exhibit fluorescence from locally excited states, consistent with their large singlet-triplet energy gaps. Additionally, the cyclisation of aryl propargyl ethers, 4-diphenylbut-1-yne and a tosyl-protected propargylaniline afforded sulfenylated 6-membered products (7 examples, up to 94% yield). Density functional theory (DFT) calculations, corroborated by initial kinetics, helped to understand the order and rate of the reaction and support a mechanism in which thiirenium ions are involved as key intermediates in the formation of the observed products.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Chemistry Research Institutes & Centres > Cardiff Catalysis Institute (CCI)
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/3.0/, Start Date: 2026-04-29
Publisher:	Royal Society of Chemistry
ISSN:	2041-6520
Date of First Compliant Deposit:	15 May 2026
Date of Acceptance:	20 April 2026
Last Modified:	02 Jul 2026 11:28
URI:	https://orca.cardiff.ac.uk/id/eprint/187014

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