Halogen-bonding-induced diverse aggregation of 4,5-diiodo-1,2,3-triazolium salts with different anions

• Xingyu Xu,
• Shiqing Huang,
• Zengyu Zhang,
• Lei Cao and
• Xiaoyu Yan

Beilstein J. Org. Chem. 2020, 16, 78–87, doi:10.3762/bjoc.16.10

• candidates for XB donors, which is mainly due to the ease of preparation via a copper-catalyzed click reaction between azide and alkyne [38][39]. 1,2,3-Triazoles and 1,2,3-triazolium-based XB activators have been found applications in catalytic reactions [40][41] and anion recognition [42]. Recently, we

Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction

• Renata Kaczmarek,
• Dariusz Korczyński,
• James R. Green and
• Roman Dembinski

Beilstein J. Org. Chem. 2020, 16, 1–8, doi:10.3762/bjoc.16.1

• carbon monoxide-releasing properties [27][28] of dicobalt hexacarbonyl alkyne complexes have been noted, and their medicinal potential has been summarized [29][30][31]. Despite developments, the collection of metallo-nucleosides is limited. Hybridization of alkyl and aryl-substituted alkyne cobalt

• -acetate hexacarbonyl dicobalt complexes and a Lewis or Brønsted acid. A range of heteroatom nucleophiles have been incorporated into alkyne dicobalt complexes by this chemistry [34][35][36][37][38][39][40]. However, reactions with carbon-based nucleophiles provide an opportunity to access the structurally

• warranted, which at the same time may provide biologically active compounds. Results and Discussion Preparation of 5-alkynyluridines was carried out from acyl-protected 5-iodouridines (1a,b) [8][63] and the appropriate terminal alkyne in the presence of catalytic amounts of Pd(PPh3)4, copper(I) iodide

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

• Zachary Lee,
• Brandon R. Jones,
• Nyochembeng Nkengbeza,
• Michael Phillips,
• Kayla Valentine,
• Alexis Stewart,
• Brandon Sellers,
• Nicholas Shuber and
• Karelle S. Aiken

Beilstein J. Org. Chem. 2019, 15, 2747–2752, doi:10.3762/bjoc.15.265

• of the α-iodo intermediate, and methodology studies demonstrate that alkyl-capped, asymmetric, internal alkynes undergo a regiospecific hydration, also via the 5-exo-dig NGP pathway. Keywords: α-iodo intermediate; internal alkyne; iodine-mediated hydration; neighboring group participation

• innocuous, water-soluble byproducts, such as iodide and sulfate salts, and uses inexpensive molecular iodine to facilitate the hydration. Moreover, unlike other metal-free alkyne hydration procedures, heat and strong acids are not required [17][18][19][20]. The reaction proceeds under mild conditions at

• intermediate 9, we turned our attention to investigating the reaction of internal alkynes 11 to examine the regioselectivity of the hydration process. Ester, sulfone, and phosphonate substrates were employed and, in all cases, the internal alkyne unit was capped by an ethyl group (Scheme 2). In general

Fluorinated maleimide-substituted porphyrins and chlorins: synthesis and characterization

• Valentina A. Ol’shevskaya,
• Elena G. Kononova and
• Andrei V. Zaitsev

Beilstein J. Org. Chem. 2019, 15, 2704–2709, doi:10.3762/bjoc.15.263

• 1,2,3-triazole heterocycles via the copper-catalyzed azide–alkyne cycloaddition reaction (CuAAC) between alkynes and azides, developed independently by Sharpless [41] and Meldal [42]. In addition to the applications of triazoles as pharmacophores in the potential biologically active molecules, these

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

• to α-pyrones through a consecutive alkynylation–Michael addition–cyclocondensation (AMAC) multicomponent synthesis [23]. The reaction can be rationalized by a Sonogashira coupling between an acid chloride and a terminal alkyne furnishing an alkynone, which is transformed without isolation by addition

AgNTf₂-catalyzed formal [3 + 2] cycloaddition of ynamides with unprotected isoxazol-5-amines: efficient access to functionalized 5-amino-1H-pyrrole-3-carboxamide derivatives

• Ziping Cao,
• Jiekun Zhu,
• Li Liu,
• Yuanling Pang,
• Laijin Tian,
• Xuejun Sun and
• Xin Meng

Beilstein J. Org. Chem. 2019, 15, 2623–2630, doi:10.3762/bjoc.15.255

• attracted much attention over the past decade [1][2]. As a powerful π-activator, silver can promote various reactions of alkynes in high efficiencies [3][4][5][6][7][8]. Generally speaking, the proceeding of these reactions involves the activation of alkyne bond by coordination of [Ag] and then the

• carbene pathway presumed by mechanistic studies and theoretical calculations. Following our ongoing interest in the alkyne chemistry [36][37][38], we recently envisaged that the reaction of ynamides with isoxazoles could proceed under silver catalysis conditions, involving the generation of α-imino silver

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• resulting rhodamine 28c could be a possible substrate for the conversion into an azide and follow-up click reactions with alkyne-substituted tumor vectors. While heating of amine 28a to the corresponding boroxine 28b lead to formation of a brown solid (presumably due to degradation), the reaction of

Formation of alkyne-bridged ferrocenophanes using ring-closing alkyne metathesis on 1,1’-diacetylenic ferrocenes

• Celine Bittner,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2019, 15, 2534–2543, doi:10.3762/bjoc.15.246

• Celine Bittner Dirk Bockfeld Matthias Tamm Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, 38102 Braunschweig, Germany 10.3762/bjoc.15.246 Abstract Novel alkyne-bridged ferrocenophanes [fc{CO2(CH2)nC≡}2] (2a: n = 2; 2b: n = 3) were synthesized

• from the corresponding terminal diacetylenic ferrocenes [fc{CO2(CH2)nC≡CH}2] (1a: n = 2; 1b: n = 3) through ring-closing alkyne metathesis (RCAM) utilizing the highly effective molybdenum catalyst [MesC≡Mo{OC(CF3)2CH3}3] (MoF6; Mes = 2,4,6-trimethylphenyl). The metathesis reaction occurs in short time

• isolated from THF solution. Keywords: alkyne metathesis; ferrocene; homogeneous catalysis; molybdenum; terminal alkynes; Introduction Alkyne metathesis, the reversible making and breaking of carbon–carbon triple bonds, is clearly gaining more attention. Not only could a great number of active catalysts

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• latter one. One of the main reasons is that an azobenzene has a relatively simple structure that can resemble various biaryl moieties of bioactive compounds: two aromatic rings linked with a bridge (e.g., amide, ether, alkane or alkyne) [8]. In the case of azobenzene the bridge is a diazene group (also

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• catalysis has proved its effectiveness for numerous transformations involving unsaturated bond activation (allene, alkyne, alkene) [11][12][13][14][15][16][17], radical-based reactions [18][19][20] and several applications in asymmetric reactions [21][22]. This successful chemistry was usually conducted in

• . In our control experiment, alkyne 2 was converted into product 4 in high yield (88 %) using AgOTf at 5 mol % (Table 1, entry 1). Interestingly, 1-methoxyisochromene 4 can also be isolated in 89% yield, using a AgOTf catalytic loading of 1 mol % (Table 1, entry 2). All silver complexes 1a–d (1 mol

• slowly added to afford a precipitation. After filtration, the isolated solid was washed with diethyl ether and dried under vacuum. General procedure for the acetalization/cycloisomerization of alkyne 2: An oven-dried Schlenk tube was charged with the silver(I) catalyst (0.5–5 mol %), then degassed and

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• moiety. The effect of the R1 substituent at the tetrazole ring and the aryl substituents of the alkyne (Ar, Scheme 1) on the efficiency of the annulation reaction were also evaluated. As shown in Scheme 4, the system is tolerant to a variety of substituents R1 (originating from the isocyanide component

• ), isocyanide (1.1 equiv) and TMSN3 (1.1 equiv) in EtOH at 100 °C (MW radiation, two cycles of 15 min each). Influence of substituents R and R2 on the reaction outcome. For compounds 4k–m the overall yield in parentheses refers to the mixture of regioisomers. Influence of the alkyne and R1 substituent on the

Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation

• Andreas Boelke,
• Yulia A. Vlasenko,
• Mekhman S. Yusubov,
• Boris J. Nachtsheim and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2019, 15, 2311–2318, doi:10.3762/bjoc.15.223

• of group-transfer reactions. Prominent examples include ethynyl benziodoxolones (EBX, L1 = alkyne) [12], the Zhdankin reagent azidobenziodoxole (ABX, L1 = N3) [13], cyanobenziodoxole (CBX, L1 = CN) [14] or Togni’s reagent (L1 = CF3) [15]. Even though the transferable ligand (L1) has been varied

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• electron-rich unsaturated bonds (arene, alkene, or alkyne), or a substrate having a nucleophilic and labile bond (e.g., C−Si, C−Sn, and C−B), while the electrophile is the fluorination reagent (Scheme 1b). As shown in Scheme 1d, many nucleophilic and electrophilic fluorination reagents have been developed

Click chemistry towards thermally reversible photochromic 4,5-bisthiazolyl-1,2,3-triazoles

• Chenxia Zhang,
• Kaori Morinaka,
• Mahmut Kose,
• Takashi Ubukata and
• Yasushi Yokoyama

Beilstein J. Org. Chem. 2019, 15, 2161–2169, doi:10.3762/bjoc.15.213

• century, Sharpless and co-workers proposed the concept of “click chemistry” [14], which stands for the secure, quick, selective, general and facile reaction between two organic functional groups. In click chemistry, the Huisgen cyclization, which occurs between an organic azide and a terminal alkyne

• important difference is that Ru(I) catalysts work on the disubstituted alkynes to give 1,4,5-trisubstituted triazoles (Scheme 1) [18][19]. When both substituents of an internal alkyne are aromatic groups, the triazoles thus formed include the hexatriene motif in the structure. Although a number of

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• (iodine, bromine) and chalcogens (selenium and tellurium) [18]. While there are several strategies for the synthesis of triazoles, the Cu(II)-catalyzed azide–alkyne cycloaddition reaction (CuAAC click reaction) is considered as one of the most efficient, simple and mild approaches towards the preparation

• of 1,4-disubstituted 1,2,3- triazole units [19][20][21][22][23][24]. Macrocyclic ring closure can be achieved by the CuAAC of building blocks functionalized with both azide and alkyne, using [1 + 1], [2 + 2], [n + n] strategies depending on how much triazoles are needed to be included in the

Archangelolide: A sesquiterpene lactone with immunobiological potential from Laserpitium archangelica

• Silvie Rimpelová,
• Michal Jurášek,
• Lucie Peterková,
• Jiří Bejček,
• Vojtěch Spiwok,
• Miloš Majdl,
• Michal Jirásko,
• Miloš Buděšínský,
• Juraj Harmatha,
• Eva Kmoníčková,
• Pavel Drašar and
• Tomáš Ruml

Beilstein J. Org. Chem. 2019, 15, 1933–1944, doi:10.3762/bjoc.15.189

• studied by us and others, there are only scarce reports on the biological activity of archangelolide. Here we present the preparation of its fluorescent derivative based on a dansyl moiety using azide–alkyne Huisgen cycloaddition having obtained the two sesquiterpene lactones from the seeds of Laserpitium

• these compounds for further work including synthetic modifications using azide–alkyne Huisgen cycloaddition. We previously showed the preparation of fluorescent trilobolide conjugates [8] that retained the activity of the parental compounds and proved to be useful for live-cell imaging. In this article

Synthesis of a [6]rotaxane with singly threaded γ-cyclodextrins as a single stereoisomer

• Jason Yin Hei Man and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2019, 15, 1829–1837, doi:10.3762/bjoc.15.177

• azide–alkyne cycloaddtion (CBAAC) with the anthracene-derived propagylamine stopper 2. In CBAAC, the strong ammonium–CB[6] binding places the alkyne and azide in a close proximity inside the CB[6] cavity and facilitates the cycloaddition [40][41][42]. Since CB[6] binding is required for the covalent

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• react with aldehydes 1 in the presence of NaHSO4·SiO2 and the product obtained was refluxed with phenylacetylene (as terminal alkyne, 2) in the presence of CuI to obtain the product, however, in the second pathway, 1 and 2 were taken together in the presence of CuI and the product obtained was treated

• ). However, the reaction was unsuccessful with aliphatic and low-boiling aldehydes (as the reaction was taking place at high temperature). The reaction mechanism involved a Cu-NPs-mediated C–H bond activation of the alkyne which further reacted with the iminium ion to form propargylamine 45 and Cu NPs were

• might be due to the formation of Cu(II)-mediated propargylamine 68 from the alkyne and Schiff base-copper complex that was cyclized and aromatized to form the target compound 67 (Scheme 24). Kumar et al. have described a Cu(OTf)2-catalyzed three-component reaction for the synthesis of imidazo[1,2-a

One-pot activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazolines in a consecutive three-component fashion

• Christina Görgen,
• Katharina Boden,
• Guido J. Reiss,
• Walter Frank and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 1360–1370, doi:10.3762/bjoc.15.136

• multicomponent reactions [43][44][45][46][47]. Particularly interesting are alkynediones, because, as densely functionalized trielectrophiles, the alkyne, ynone and dicarbonyl functionalities can be selectively addressed. We have established two complementary one-pot pathways to alkynediones, a glyoxylation

Remarkable effect of alkynyl substituents on the fluorescence properties of a BN-phenanthrene

• Alberto Abengózar,
• David Sucunza,
• Patricia García-García and
• Juan J. Vaquero

Beilstein J. Org. Chem. 2019, 15, 1257–1261, doi:10.3762/bjoc.15.122

• impressive effect of the presence of alkynyl substituents on the fluorescence quantum yield, which improved from 0.01 in the parent compound to up to 0.65 in derivatives containing a triple bond. Keywords: alkyne; BN-phenanthrene; cross-coupling; fluorescence; heterocycles; Introduction BN-polycyclic

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• as the conjugation of steroids to amino acids, peptides and carbohydrates. We demonstrate that steroids are available with almost all types of MCR reactive functionalities, e.g., carbonyl, carboxylic acid, alkyne, amine, isocyanide, boronic acid, etc., and that steroids are suitable starting

Insertion of [1.1.1]propellane into aromatic disulfides

• Robin M. Bär,
• Gregor Heinrich,
• Martin Nieger,
• Olaf Fuhr and
• Stefan Bräse

Beilstein J. Org. Chem. 2019, 15, 1172–1180, doi:10.3762/bjoc.15.114

• as bioisosters of para-substituted benzene and alkyne moieties. The most promising precursor for BCPs is [1.1.1]propellane (1). The available methods to synthesize BCPs are quite limited and many groups contribute to the development of novel methods. The insertion of 1 into disulfide bonds is known

• materials science and medicinal chemistry [1]. Often referred to as bioisosteres, small strained hydrocarbons are used to replace phenyl [2][3][4] or alkyne groups [5] in well-known compounds, e.g., imatinib [3] and tazarotene [5]. The increase of the three-dimensionality and the disruption of the π-system

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• similar way to that described in Scheme 3. In this case, the coupled alkyne moiety is again activated by Cu(I) and then base-promoted cyclization occurs. A new copper complex formation with the alkene analogue to 13 (see Scheme 3) facilitates the aromatic nucleophilic substitution by indole or pyrrole

• , leading to final lactams 20. This mechanism is partially corroborated by the following multicomponent synthesis where benzamide 21, ortho-functionalized with a terminal alkyne group (Scheme 5), a secondary amine 22 and carbon monoxide (23) react to produce 3-methyleneisoindolinones 24 [80]. A palladium

• conjugate addition of benzamide nitrogen onto the 2-ynamide generates the final cyclization product 24 through allene intermediate 28. Taking into account that the reaction does not take place with internal alkynes, the authors conclude that a terminal alkyne is necessary for the formation of the first

A three-component, Zn(OTf)₂-mediated entry into trisubstituted 2-aminoimidazoles

• Alexei Lukin,
• Anna Bakholdina,
• Anna Kryukova,
• Alexander Sapegin and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2019, 15, 1061–1064, doi:10.3762/bjoc.15.103

• propargylureas (leading to 2-imidazolones) and extend the range of Lewis acid-catalyzed azole syntheses based on N-carbonyl propargylamines. Keywords: alkyne hydroamination; cyclocondensation; Lewis acid catalysis; multicomponent reactions; propargylurea; Introduction The pioneering publications of Beller and

• the mechanistic prospective, the reaction probably proceeds via Zn(OTf)2-catalyzed alkyne hydroamination followed by cyclodehydration as depicted in Figure 3, in full analogy with the previously proposed mechanism [2][3]. Conclusion In summary, we have successfully employed propargylureas in the

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102