CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

Hydrazides in the reaction with hydroxypyrrolines: less nucleophilicity – more diversity

• Dmitrii A. Shabalin,
• Evgeniya E. Ivanova,
• Igor A. Ushakov,
• Elena Yu. Schmidt and
• Boris A. Trofimov

Beilstein J. Org. Chem. 2021, 17, 319–324, doi:10.3762/bjoc.17.29

• saturated pyridazine scaffolds is both highly topical and necessary. Recently, we have developed a convenient approach to the 1,4-dihydropyridazine core based on the Brønsted acid-catalyzed regioselective recyclization of 5-hydroxypyrrolines (assembled in a one-pot manner from ketoximes and acetylene gas [8

• formation of 1,4-dihydropyridazine 4. Conclusion In summary, an acid-catalyzed recyclization of hydroxypyrrolines (easily synthesized from ketoximes and acetylene) with hydrazides was studied. The reduced nucleophilicity of the hydrazides in comparison with other hydrazine derivatives constitutes the basis

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• , and diisopropylethylamine in the presence of quinidine TMS ether (TMSQD) according to Nelson’s procedures [53][54][55] provided the enantioenriched β-lactone (−)-79b in 85% yield. The desired terminal acetylene (−)-82b was synthesized from β-lactone (−)-79b following a three-step sequence as shown in

• -catalyzed hydroboration of the terminal acetylene in 127 gave (E,E)-128 in good yield and with complete stereocontrol (Scheme 18). To accomplish the key Suzuki coupling of dienylboronic ester 128, the necessary alkenyl iodides (Z)- and (E)-130 were prepared from the propargyl alcohol (14) in good yields

Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

• Vladimir Ilkin,
• Vera Berseneva,
• Tetyana Beryozkina,
• Tatiana Glukhareva,
• Lidia Dianova,
• Wim Dehaen,
• Eugenia Seliverstova and
• Vasiliy Bakulev

Beilstein J. Org. Chem. 2020, 16, 2937–2947, doi:10.3762/bjoc.16.243

• corresponding amides 4a–d by treatment with phosphorus decasulfide (Scheme 1). It is worth noting that amides of 1-alkyl-1,2,3-triazole-4-carboxylic acids are poorly represented in the literature and the methods of their preparation require the addition of alkyl azides to acetylene carboxylic esters and

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• ppm in the 13C NMR spectrum were attributed to the acetylene protons and carbons, respectively. The electrospray ionization (ESI) mass spectrum showed the most intense peak at m/z 641.1923, which corresponds to the [M + Na]+ molecular adduct ion and matches well with the calculated value (m/z 641.1935

Formation of an exceptionally stable ketene during phototransformations of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores

• Asitanga Ghosh

Beilstein J. Org. Chem. 2020, 16, 2297–2303, doi:10.3762/bjoc.16.190

• ][18] and dibenzoyl acetylene (9) followed by hydrolysis of the silyloxy adduct (Scheme 4). Both 7a and 7b showed an enhanced (n,π*) absorption band near 300 nm (log ε ≈ 3.5) along with an additional weak band near 343 nm (log ε ≈ 2.5) in their UV spectra as expected for δ-keto-α,β-enone [7

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• derivatives 3a–d/g–k/m–q in a yield of 70–88%. Distinctively, the cyano acrylate-substituted MBH adduct stereoselectively afforded the (Z)-cinnamyl-1,4-disubstituted 1,2,3-triazole derivatives 3e/f/l in a yield of 82–92%. Irrespective of the acetylene moiety, the MBH adducts derived from acrylonitrile

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• displays a Cethynyl–H···π interaction (2.530 Å) between the acetylene proton of 8j and the N-phenyl ring of the N-phenylmaleimide (7c) (Table 7, and Figure 4d and Figure 5c). Such an interaction may explain the greater stabilization of the endo approach to give 9p as the major isomer. Due to the scarce X

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• released. Alkali salts of acetylene dicarboxylic acid can also be used as precursor for the preparation of carbon spheres. The structure and morphology of the carbon spheres can be influenced by the used alkali salts [80]. Activated carbon preparation The following chapter summarizes the different

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

• complexity, by essentially using a Ru-catalyzed alkene–alkyne (Ru-AA) coupling reaction and a macrolactonization step (Scheme 8). In this carefully designed total synthesis, after applying a Marshall coupling reaction aimed at installing a propargyl group into the initial acetylene component, an enyne

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• two-component or three-component “click” reactions. In the two-component reaction, acetylene compounds and organic azides were stirred in dimethylformamide or in a mixture of t-BuOH/H2O, 3:1, v/v as the solvent using diethylisopropylamine and SiO2–Cu. In the three-component example, acetylene species

• “click” reactions of alkyl halide, NaN3, and acetylene were performed successfully in the presence of 100 (1.0 mol %) as the catalyst and 10 mol % of sodium ascorbate as a reducing agent in water at 50 °C (Scheme 22). Further, the nanocatalyst 100 was durable and could be recycled eight times without any

Palladium-catalyzed Sonogashira coupling reactions in γ-valerolactone-based ionic liquids

• László Orha,
• József M. Tukacs,
• László Kollár and
• László T. Mika

Beilstein J. Org. Chem. 2019, 15, 2907–2913, doi:10.3762/bjoc.15.284

• iodide (Table 3, entries 2–7). Under identical conditions, 2-iodothiophene, and iodopyridine derivatives could also easily be converted to the corresponding acetylene with good or even excellent isolated yields (3i–n). When 2-amino-3-iodopyridine (1i) was converted no C–N bond formation was detected

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

• solid. The metathesis reactions were performed in the presence of molecular sieves with a pore size of 5 Å (MS 5 Å) to absorb acetylene which is formed during the reaction. The products of the metathesis reactions could be obtained as orange solids. The RCAM of the butynyl system 1a afforded the desired

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

• peptides and the formation of isoquinolones; so it is expected that in intermediate B the substrate behaves as a tridentate ligand for the Rh(III) center [37][62][63][64][65]. However, such a complexation must be reversible to allow a further ligand exchange with the acetylene to form intermediate C. The

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• ][150][159][164][175][211] derivatives [174][183][200][229] are often used as the complementary dienophiles (Scheme 14, reaction pathways (i), (ii) and (iii), respectively), as well as mono- and disubstituted acetylene derivatives, such as methyl propiolate [229] and dibenzoylacetylene [150]. Conversely

Nanopatterns of arylene–alkynylene squares on graphite: self-sorting and intercalation

• Tristan J. Keller,
• Joshua Bahr,
• Kristin Gratzfeld,
• Nina Schönfelder,
• Marcin A. Majewski,
• Marcin Stępień,
• Sigurd Höger and
• Stefan-S. Jester

Beilstein J. Org. Chem. 2019, 15, 1848–1855, doi:10.3762/bjoc.15.180

• other sides of the square is based on the Glaser coupling of acetylene-terminated precursor structures. These side chains give macrocycles with reduced symmetry. They cannot be obtained by the cyclization of small building blocks, but require the stepwise formation of more complex precursors, where the

• protective groups [28]. Subsequently, 1a/b were prepared by Pd-catalyzed oxidative cyclodimerization of the respective acetylene-terminated precursors under high-dilution conditions [29][30]. The separation of the crude products by recycling gel permeation chromatography (recGPC) yielded the monodisperse

Norbornadiene-functionalized triazatriangulenium and trioxatriangulenium platforms

• Roland Löw,
• Talina Rusch,
• Tobias Moje,
• Fynn Röhricht,
• Olaf M. Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1815–1821, doi:10.3762/bjoc.15.175

• the mechanisms of bulk metal catalysis and open new ways to design new catalytic systems. Towards this end, and following the “platform concept”, we designed a cyano-substituted norbornadiene, which is functionalized with an acetylene spacer on a TATA platform to investigate an eventual “spin

• triazatriangulenium ion 6 was synthesized according to a procedure of Laursen and Krebs [13]. The platform 6 was functionalized with norbornadiene 5 by deprotection of the acetylene with potassium hydroxide and in situ formation of the C–C bond between the acetylene and the central C atom of the platform 6 to yield

• ) crossection along the white line in (a). Syntheses of the norbornadiene TATA platform 1 and TOTA platform 3. a) TMS-acetylene, Pd(PPh3)4, Cu(I)I, Et3N, toluene, N2, 60 °C, 1.3 h; b) KOH, THF, N2, reflux, 5 h; c) sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBArF4), DCM, rt, 2 h; d) n-BuLi, THF, N2

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• dyes. Synthetic scheme of the selected materials. a) hydroxylamine hydrochloride, NaHCO3, DMSO, 60 °C then acetylene, KOH, DMSO, 110 °C, 24% over the two steps; b) 4-iodobenzoyl chloride, DCM, rt then DDQ, DCM, rt then NEt3, BF3·OEt2, 0 °C to rt, 35%; c) piperidine, cat. PTSA, toluene, 130 °C, 5: 35

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

• groups (EDGs) at different positions on the phenyl ring. However, the use of aliphatic aldehydes such as 3-methylbutanal and cyclohexanecarbaldehyde and aliphatic acetylene viz., hex-1-yne resulted in a comparatively lower yield of 66, 70 and 60%, respectively. Heteroaromatic aldehydes such as thiophene

Synthesis of ([1,2,4]triazolo[4,3-a]pyridin-3-ylmethyl)phosphonates and their benzo derivatives via 5-exo-dig cyclization

• Aleksandr S. Krylov,
• Artem A. Petrosian,
• Julia L. Piterskaya,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2019, 15, 1563–1568, doi:10.3762/bjoc.15.159

• , hypervalent iodine reagents, etc. The synthetic methods towards diverse [1,2,4]triazolo[3,4-a]pyridines have been reviewed in detail [12][13]. It should be noted that the use of acetylene species to create this heterocycle (including triazole ring) is presented only by few examples. There has been reported

• one method for the formation of a [1,2,4]triazolo[4,3-a]pyridine ring with participation of an acetylene triple bond; an oxidative cyclization during the reaction of terminal phenylacetylenes with 2-hydrazinylpyridines [14]. However, data on phosphorus-containing triazolopyridines are scarce, although

Different reactivity of phosphorylallenes under the action of Brønsted or Lewis acids: a crucial role of involvement of the P=O group in intra- or intermolecular interactions at the formation of cationic intermediates

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1491–1504, doi:10.3762/bjoc.15.151

• considered (Scheme 10). The required catalytic amount of such superacid may be formed due to the presence of traces of HCl (byproduct in acetylene–allene rearrangement step) in the reaction mixture. Next, the protonaton of complex 13 occurs, leading to allylic cation 22. As analogue of cation 16 (Scheme 9

Diazocine-functionalized TATA platforms

• Roland Löw,
• Talina Rusch,
• Fynn Röhricht,
• Olaf Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1485–1490, doi:10.3762/bjoc.15.150

• platform (triazatriangulenium (TATA)) which adsorbs on the gold surface, with an acetylene spacer standing upright, like a post in the middle of the platform and the azobenzene unit mounted on top. The rate acceleration is due to a very peculiar thermal singlet–triplet–singlet mechanism mediated by bulk

• to the trans-form, which slowly returns back to the stable cis-isomer. To investigate the thermal trans→cis isomerization as a function of the conjugation to the metal surface, we connected the acetylene spacer in meta (weak conjugation) and in para (strong conjugation) position. Both isomers form

• a function of electronic coupling (conjugation) of the azo unit to gold. The para-diazocine-TATA 1 was synthesized in a 5-step synthesis route (Scheme 1). Bromotoluene 3 was synthesized as described [26]. In a Sonogashira cross-coupling reaction acetylene-substituted toluene 5 was prepared from

Synthesis of dipolar molecular rotors as linkers for metal-organic frameworks

• Sebastian Hamer,
• Fynn Röhricht,
• Marius Jakoby,
• Ian A. Howard,
• Xianghui Zhang,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1331–1338, doi:10.3762/bjoc.15.132

• Sonogashira reactions [53]. In the reported procedure, a bulky substituted acetylene derivative was used, probably supressing the formation of the phthalocyanine byproduct to some extent. Indeed, 5,6-dicyano-4,7-bis-(2-trimethylsilylethynyl)-2,1,3-benzothiadiazole (12a) could be synthesized by Sonogashira

• polymerisation of the acetylides. No deprotected terminal acetylene was observed. To avoid polymerization, the solvent was changed to acetonitrile and the temperature was lowered to 0 °C. Additionally, carbon dioxide was not just used as the reaction atmosphere, but directly bubbled through the solution

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• followed by acetylene–allene rearrangement was used to prepare (arylsulfinyl)allenes 1 according to the literature procedure [24][25]. The latter were in situ oxidized to (arylsulfonyl)allenes 2 (see X-ray structure of 2h in Figure 1). Allenes 1a,b were specially isolated to compare their reactivity with

Domino ring-opening–ring-closing enyne metathesis vs enyne metathesis of norbornene derivatives with alkynyl side chains. Construction of condensed polycarbocycles

• Ritabrata Datta and
• Subrata Ghosh

Beilstein J. Org. Chem. 2018, 14, 2708–2714, doi:10.3762/bjoc.14.248

• polycycles from metathesis of norbornene derivatives with alkynyl side-chain. This investigation demonstrated that domino metathesis of norbornene derivatives with alkynyl side-chain requires metathesis initiation at the acetylene unit. Further, the nature of functional groups as well as the substrate