molecules Article Synthesis of 4-Arylselanyl-1H-1,2,3-triazoles from Selenium-Containing Carbinols Francesca Begini 1, Renata A. Balaguez 2, Allya Larroza 2, Eric F. Lopes 2 , Eder João Lenardão 2 , Claudio Santi 1 and Diego Alves 2,* 1 Group of Catalysis, Synthesis and Organic Green Chemistry, Department of Pharmaceutical Sciences University of Perugia Via del Liceo 1, 06123 Perugia, Italy; [email protected] (F.B.); [email protected] (C.S.) 2 LASOL-CCQFA, Universidade Federal de Pelotas-UFPel, P.O. Box 354, 96010-900 Pelotas, Brazil; [email protected] (R.A.B.); [email protected] (A.L.); [email protected] (E.F.L.); [email protected] (E.J.L.) * Correspondence: [email protected]; Tel.: +55-53-32757533 Abstract: In this work, we present a simple way to achieve 4-arylselanyl-1H-1,2,3-triazoles from selenium-containing carbinols in a one-pot strategy. The selenium-containing carbinols were used as starting materials to produce a range of selanyl-triazoles in moderate to good yields, including a quinoline and Zidovudine derivatives. One-pot protocols are crucial to the current concerns about waste production and solvent consumption, avoiding the isolation and purification steps of the reactive terminal selanylalkynes. We could also isolate an interesting and unprecedented by-product with one alkynylselenium moiety connected to the triazole. Keywords: selenium; 1,2,3-triazoles; click chemistry; cycloaddition; carbinols; heterocycles Citation: Begini, F.; Balaguez, R.A.; Larroza, A.; Lopes, E.F.; Lenardão, E.J.; Santi, C.; Alves, D. Synthesis of 1. Introduction 4-Arylselanyl-1H-1,2,3-triazoles from Selenium-Containing Carbinols. Triazoles are a significant class of heterocycles which have received considerable Molecules 2021, 26, 2224. https:// attention because of their application in materials science, medicinal chemistry and or- doi.org/10.3390/molecules26082224 ganic synthesis [1–3]. Particularly, 1,2,3-triazoles derivatives exhibit a broad spectrum of biological properties, such as anti-inflammatory, antifungal, antibacterial, anticancer, Academic Editor: Georg Manolikakes antivirus and antituberculosis [4–13]. 1,2,3-Triazoles derivatives are an important con- necting group, linking a broad range of substituted substrates in a simple fashion, being Received: 25 March 2021 used as peptide mimetics [14,15]. Inspired in the Huisgen [3 + 2] cycloaddition reaction of Accepted: 9 April 2021 an organic azide and a terminal alkyne [16], a number of catalytic strategies employing Published: 12 April 2021 transition metals have been used to address the reactivity and selectivity issues inherent to the seminal strategy [17–26]. In addition, recent studies have been directed toward the de- Publisher’s Note: MDPI stays neutral velopment of metal-free methodologies for triazole synthesis. Organocatalytic approaches with regard to jurisdictional claims in involving [3 + 2] cycloaddition have been reported for the synthesis of functionalized published maps and institutional affil- 1,2,3-triazoles [27–34]. iations. Despite the significant advances toward the synthesis of highly substituted 1,2,3- triazoles, the need of a deep study on the combinations of substrates for the synthe- sis of highly functionalized and complex structures is still an open issue. In this sense, organoselanyl-triazoles constitute an interesting class of molecules, which combine the Copyright: © 2021 by the authors. importance of a triazole nucleus [1–3] with an organoselenium moiety [35–38]. Selenium is Licensee MDPI, Basel, Switzerland. an essential nutrient for mammals, playing important roles in metabolic pathways [39,40], This article is an open access article and the interest in selenium pharmacology [41–46] and chemistry [47–49] has increased in distributed under the terms and this century. conditions of the Creative Commons Several methodologies have been reported for the selective synthesis of a range of Attribution (CC BY) license (https:// 1,2,3-triazole scaffolds containing an organoselenium moiety [50–52]. However, only a few creativecommons.org/licenses/by/ procedures to directly prepare 5-arylselanyl- and 4-arylselanyl-1H-1,2,3-triazoles have been 4.0/). Molecules 2021, 26, 2224. https://doi.org/10.3390/molecules26082224 https://www.mdpi.com/journal/molecules Molecules 2021, 26, x FOR PEER REVIEW 2 of 11 Molecules 2021, 26, 2224 2 of 11 few procedures to directly prepare 5-arylselanyl- and 4-arylselanyl-1H-1,2,3-triazoles have been described (Figure 1). For example, Cui et al. developed a simple and efficient describedmethod (Figurefor the1 ).preparation For example, of Cui 5-arylselanyl-1 et al. developedH-1,2,3-triazoles a simple and efficient from methodpropiolic for acids, the preparationdiselenides of and 5-arylselanyl-1 azides, in whichH-1,2,3-triazoles a selanylalk fromyne propiolicwas firstly acids, formed diselenides via decarboxylative and azides, inreactions, which a selanylalkynefollowed by wasthe intermolecular firstly formed via copper-catalyzed decarboxylative azide-alkyne reactions, followed cycloaddition by the intermolecularreaction (CuAAC) copper-catalyzed to afford the azide-alkyne desired produc cycloadditionts [53]. Wang reaction et al. (CuAAC) described to affordthe use the of desiredPhSO2SePh products as an [53 electrophile]. Wang et al. in described the copper the use(I)-catalyzed of PhSO2SePh interrupted as an electrophile click reaction in the of copperphenylacetylene (I)-catalyzed with interrupted benzylaz clickide, reactiongiving of5-arylselanyl-1 phenylacetyleneH-1,2,3-triazole with benzylazide, in 71% giving yield 5-arylselanyl-1[54]. ManarinH et-1,2,3-triazole al. developed in a 71%general yield me [54thod]. Manarin for the synthesis et al. developed of 4-arylselanyl-1 a general methodH-1,2,3- fortriazoles the synthesis via a ofCuAAC 4-arylselanyl-1 reactionH between-1,2,3-triazoles organic via azides a CuAAC and reactiona terminal between selanylalkyne, organic azidesgenerated and aby terminal the in situ selanylalkyne, deprotection generatedof the silyl by group the in[55]. situ The deprotection synthesis of of 1-benzyl-4- the silyl group(phenylselanyl)-1 [55]. The synthesisH-1,2,3-triazole of 1-benzyl-4-(phenylselanyl)-1 was described byH -1,2,3-triazoleSaraiva et wasal., described in which by Saraivaethynyl(phenyl)selenide et al., in which ethynyl(phenyl)selenide underwent CuAAC with underwent benzylazide CuAAC to give with the benzylazide product in 84% to giveyield the [56]. product However, in 84% for yield the [synthesis56]. However, of ethy fornyl(phenyl)selenide, the synthesis of ethynyl(phenyl)selenide, the protocol available theat the protocol time to available achieve atsuch the starting time to material achieve was such described starting materialby Braga was et al., described dating from by Braga1994 et[57]. al., Recently, dating from we 1994have [57developed]. Recently, an wealternative have developed way to prepare an alternative these wayterminal to preparealkynes these containing terminal selenium alkynes containingand sulfur, selenium starting andfrom sulfur, chalcoge startingn-containing from chalcogen- alkynyl containingcarbinols [58]. alkynyl In this carbinols study, during [58]. In the this preparation study, during of the the terminal preparation selanylalkynes, of the terminal it was selanylalkynes,observed that in it air was without observed solvent, that inthese air compounds without solvent, showed these signals compounds of decomposition. showed signalsFurthermore, of decomposition. we observed Furthermore, that in a hexane we observed solution, that inthe a hexaneterminal solution, selanylalkynes the terminal were selanylalkynesstable in the werepresence stable of in air. the presenceWith these of air.observations With these in observations mind, we inwondered mind, we if wonderedselanylalkynylcarbinols if selanylalkynylcarbinols could serve could as starting serve asmaterials starting for materials the synthesis for the of synthesis a rangeof ofa 4- rangearylselanyl-1 of 4-arylselanyl-1H-1,2,3-triazolesH-1,2,3-triazoles in a one-pot in aprocedure. one-pot procedure. FigureFigure 1. 1.Previous Previous protocols protocols to to prepare prepare 5-arylselanyl- 5-arylselanyl- and and 4-arylselanyl-1 4-arylselanyl-1HH-1,2,3-triazoles.-1,2,3-triazoles. InIn view view of theof above,the above, and in and continuation in continua to ourtion research to our endeavors research in endeavors the development in the ofdevelopment efficient and selectiveof efficient methods and selective to access methods functionalized to access selanyl-1,2,3-triazoles, functionalized selanyl-1,2,3- we report hereintriazoles, a one-pot we report strategy herein to preparea one-pot 4-arylselanyl-1 strategy to prepareH-1,2,3-triazoles, 4-arylselanyl-1 startingH-1,2,3-triazoles, from easily availablestarting from and bench-stable easily available selanylalkynylcarbinols and bench-stable selanylalkynylcarbinols and organic azides (Scheme and organic1). azides (Scheme 1). Molecules 2021, 26, x FOR PEER REVIEW 3 of 11 Scheme 1. Synthesis of 4-arylselanyl-1H-1,2,3-triazoles from selenium-containing carbinols. 2. Results and Discussion Molecules 2021, 26, 2224 3 of 11 Molecules 2021, 26, x FOR PEER REVIEW Initial experiments to optimize the reaction conditions were carried out using3 of 2-11 methyl-4-(phenylselanyl)but-3-yn-2-ol 1a and 1-azido-4-chlorobenzene 3a as standard reaction substrates (Table 1). The key step of the protocol involved the deprotection of the hydroxypropargyl