Issue 23, 2021

Visible-light photocatalytic preparation of alkenyl thioethers from 1,2,3-thiadiazoles and Hantzsch esters: synthetic and mechanistic investigations

Abstract

Herein, we disclose a protocol to synthesize trisubstituted alkenyl thioethers through a direct S-alkylation of 1,2,3-thiadiazoles with C-radical precursors, 4-alkyl-1,4-dihydropyridines (DHPs), driven by visible-light photocatalysis. A broad range of primary, secondary, and tertiary C-radical precursors, DHPs, are suitable for this reaction and the desired products can be obtained in good to excellent yields under mild conditions. Remarkably, high stereoselectivity with Z-alkenyl thioethers was achieved in the presence of a Cu(OAc)2 catalyst. Synergistic experimental and computational studies were carried out to shed light on the mechanisms of this reaction, in which the quenching pathway of an excited photocatalyst (*RuII) could be altered in the presence of the Cu(OAc)2 catalyst. A reductive quenching pathway (RuII/*RuII/RuI/RuII) is proposed in the absence of the Cu(OAc)2 catalyst while an oxidative quenching pathway (RuII/*RuII/RuIII/RuII) is suggested with the assistance of the Cu(OAc)2 catalyst. In addition, the origin of the Z-selectivity of the product is discussed.

Graphical abstract: Visible-light photocatalytic preparation of alkenyl thioethers from 1,2,3-thiadiazoles and Hantzsch esters: synthetic and mechanistic investigations

Supplementary files

Article information

Article type
Research Article
Submitted
27 Jul 2021
Accepted
04 Oct 2021
First published
05 Oct 2021

Org. Chem. Front., 2021,8, 6499-6507

Visible-light photocatalytic preparation of alkenyl thioethers from 1,2,3-thiadiazoles and Hantzsch esters: synthetic and mechanistic investigations

Z. Liang, K. Lv, S. Zhou, C. Zhu and X. Bao, Org. Chem. Front., 2021, 8, 6499 DOI: 10.1039/D1QO01076J

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