Tribromoisocyanuric acid as a useful oxidant for the synthesis of 1,3-diynes via Glaser coupling
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RIGINAL PAPER
Tribromoisocyanuric acid as a useful oxidant for the synthesis of 1,3‑diynes via Glaser coupling Vitor S. C. de Andrade1 · Marcio C. S. de Mattos1 Received: 10 June 2020 / Accepted: 10 August 2020 / Published online: 10 September 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract A simple method has been developed for homocoupling of terminal alkynes bearing different functional groups by reaction with CuI/tribromoisocyanuric acid/piperidine in acetonitrile at room temperature. A telescoped approach based on Hunsdiecker/Cadiot–Chodkiewicz reactions for C(sp)-C(sp) cross-coupling was also presented. Graphic abstract
Keywords Alkynes · One-pot synthesis · Oxidative coupling · Cross-coupling · Hunsdiecker reaction
Introduction Polyynes are a unique class of compounds in organic chemistry [1]. A subset of this large group, the 1,3-diyne moiety is fairly common in a variety naturally occurring molecules with biological properties [2, 3]. In addition to being useful synthetic building blocks, especially in polymer and supramolecular chemistry [4], these compounds have been used for the preparation of a wide range of other functionalities [5, 6]. Traditional preparation of 1,3-diynes involves the oxidative Glaser [7] and related [8–10] coupling reactions of Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00706-020-02673-8) contains supplementary material, which is available to authorized users. * Marcio C. S. de Mattos [email protected] 1
Departamento de Química Orgânica, Instituto de Química, Universidade Federal Do Rio de Janeiro, Rio de Janeiro CEP 21941‑590, Brazil
terminal alkynes through copper acetylides [11], as shown in Scheme 1. Due to the importance of carbon–carbon bond formation, many attempts have been made to improve the Glaser coupling reaction [12]. Solvent-free reactions [13] or environmentally benign solvents [14] gained considerable attention and have been increasingly reported. Other interesting approaches involve the use of different oxidants (e.g. I2 [15], NBS [16], α,α-dibromo-β-dicarbonyl compounds [17], 3,4-dihalo-2(5H)-furanones [18], among others), different metal catalysts, ligands and also utilization of alternative substrates [19]. Tribromoisocyanuric acid (1,3,5-tribromo-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, TBCA, Fig. 1) is an effective and stable electrophilic brominating reagent that can be easily prepared from readily accessible material (cyanuric acid, KBr, Oxone) [20]. From the green chemistry point of view, it presents a higher atom economy as being able to transfer up to three bromine atoms to a substrate corresponding to 66% of its mass [20]. In addition, in reactions involving TBCA,
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V. S. C. de Andrade, M. C. S. de Mattos
Scheme 1
Fig. 1 Tribromoisocyanuric acid (TBCA)
Br N
O Br
N
O N
Table 1 Optimization studies for the Glaser homocoupling of ethynylbenzene
Br
O
Base
Time
Yield / %
-
24 h
trace
Na2CO3
24 h
trace
NaOH
24 h
tra
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