1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• alkylations. Herein, the lithiated sulfur-heterocycles act as a cis-vinyl anion equivalent, a strategy that was developed by Palumbo and co-workers. The method shows some complementarity to the more classical acetylene alkylations, followed by partial hydrogenation to the cis-olefin (see Scheme 10 and Scheme

• simple linear vinyl disulfone (Scheme 8a), and by intermolecular competition experiments it was shown to be about as reactive as maleic anhydride. Benzo-1,4-dithiin-1,1,4,4-tetraoxide (7) also serves as an excellent acetylene equivalent through desulfonylation with sodium amalgam. The non-benzo-fused

Preparation of an advanced intermediate for the synthesis of leustroducsins and phoslactomycins by heterocycloaddition

• Anaïs Rousseau,
• Guillaume Vincent and
• Cyrille Kouklovsky

Beilstein J. Org. Chem. 2022, 18, 1385–1395, doi:10.3762/bjoc.18.143

• alcohol. Studies in fragment coupling We have previously reported the synthesis of the lactone fragment by catalytic asymmetric [2 + 2] cycloaddition followed by ring extension [18]. The initial product was the TMS-acetylene 18 which could be easily desilylated to give 21. However, model studies for

Synthesis of novel alkynyl imidazopyridinyl selenides: copper-catalyzed tandem selenation of selenium with 2-arylimidazo[1,2-a]pyridines and terminal alkynes

• Mio Matsumura,
• Kaho Tsukada,
• Kiwa Sugimoto,
• Yuki Murata and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 863–871, doi:10.3762/bjoc.18.87

• , under an argon atmosphere, the reaction yield decreased by approximately half. This reaction, without Na2CO3 as base, also afforded 4aa in 85% yield (Scheme 1, reaction 1). Although bis(imidazo[1,2-a]pyridin-3-yl)monoselenides 5 could form in situ [32], the reaction of 5 with acetylene 3a under the

Thiophene/selenophene-based S-shaped double helicenes: regioselective synthesis and structures

• Mengjie Wang,
• Lanping Dang,
• Wan Xu,
• Zhiying Ma,
• Liuliu Shao,
• Guangxia Wang,
• Chunli Li and
• Hua Wang

Beilstein J. Org. Chem. 2022, 18, 809–817, doi:10.3762/bjoc.18.81

• and diselenopheno[3,2-b:6,7-b′]fluorene through the cyclization of terminal acetylene as well as six types of biselenophene-based fused tricyclic derivatives [25][26]. In 2017, we reported the first member of diselenoselenophenes (DSSs), 2,5-di(trimethylsilanyl)diseleno[2,3-b:3′,2′-d]selenophene ((TMS

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• cooperative effect resulting from an additional η2-binding of the second copper(I) at the acetylene unit at which the second click reaction would take place. In case of distance mismatch, it is the formation of this copper–alkyne η2-complex that compensates for the build-up of strain as demonstrated by DFT

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• polyacetylene, with a special focus on the different possible co-conformations of the rotaxane (see Figure 7) [54]. The synthesis of the acetylene monomers 31, containing a chiral rotaxane side-chain, was achieved by tributylphosphane-catalyzed esterification. Two different macrocycles having either one BINOL

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• @PEG/Cu-Co catalyst transfers an electron from Co(III) to Cu(I). As the next step, a π complex B is formed between the metal center and the acetylene groups. A copper acetylide intermediate C is formed from complex B. The hydrophilicity of the catalyst could be increased by the use of polyethylene

• -substituted iodobenzenes catalyzed by in situ-generated α-Fe2O3 nanoparticles. One-pot synthesis of 2-arylbenzo[b]furans via tandem Sonogashira coupling–cyclization protocol. Suggested mechanism of the Fe(III) catalyzed coupling of o-iodophenol with acetylene derivatives. Fe3O4@SiO2/Schiff base/Fe(II

AlBr₃-Promoted stereoselective anti-hydroarylation of the acetylene bond in 3-arylpropynenitriles by electron-rich arenes: synthesis of 3,3-diarylpropenenitriles

• Yelizaveta Gorbunova,
• Dmitry S. Ryabukhin and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2021, 17, 2663–2667, doi:10.3762/bjoc.17.180

• , benzene and its polymethylated derivatives) under the action of aluminum bromide (AlBr3, 6 equiv) at room temperature for 0.5–2 h result in the stereoselective formation of 3,3-diarylpropenenitriles (Ar(Ar′)C=CHCN) in yields of 20–64%, as products of mainly anti-hydroarylation of the acetylene bond. The

• obtained 3,3-diarylpropenenitriles in triflic acid CF3SO3H (TfOH) at room temperature for 1 h are cyclized into 3-arylindenones in yields of 55–70%. Keywords: aluminum bromide; hydroarylation; indenones; propenenitriles; propynenitriles; Introduction Conjugated acetylene nitriles (propynenitriles, R–C≡C

• –C≡N) are versatile building blocks in organic synthesis for the preparation of a plethora of functionalized compounds and heterocycles. The presence of conjugated acetylene and nitrile bonds in these compounds leads to an enhancement of reactivity of both functional groups. Thus, propynenitriles

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation

• Azra Kocaarslan,
• Zafer Eroglu,
• Önder Metin and
• Yusuf Yagci

Beilstein J. Org. Chem. 2021, 17, 2477–2487, doi:10.3762/bjoc.17.164

• phenylacetylene (Alk-3) in the presence of copper(II) chloride/ N,N,N’,N’,N’’-pentamethyldiethylenetriamine (CuIICl2/PMDETA) and exfoliated BPNs under the white LED irradiation was performed (Figure 3). The reaction was followed by 1H NMR spectroscopy during the click process. The decrease of the acetylene proton

• reaction mixture was stirred at room temperature 24 h, then precipitated in 10-fold excess of methanol, filtered and dried in vacuum to yield PS-N3. Yield 95% (Mn,GPC: 1589 g·mol−1, Mw/Mn: 1.13). FTIR: 2096 cm−1. Synthesis of acetylene-terminated poly(ε-caprolactone) (PCL-Alk) Acetylene-terminated PCL-Alk

• acetylene proton around 4.42 ppm. a) 1H NMR spectrum of chain end modified PCL-Anth; b) UV–vis spectra of (azidomethyl)anthracene (black) and PCL-Anth (red); c) fluorescence emission spectrum of PCL-Anth. a) GPC traces of PS-Az, PCL-Alk and block copolymer (Ps-b-PCL) b) 1H NMR spectrum of the block

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• ][28][29]. In industry, pyrrole mainly comes from the extraction of coal tar, the condensation reaction of furan and ammonia under high temperature, or the cascade cyclization reaction of acetylene, formaldehyde, and ammonia. In the laboratory, there are many efficient methods for the synthesis of

Synthesis of 5-arylacetylenyl-1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions

• Andrey I. Puzanov,
• Dmitry S. Ryabukhin,
• Anna S. Zalivatskaya,
• Dmitriy N. Zakusilo,
• Darya S. Mikson,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2021, 17, 2417–2424, doi:10.3762/bjoc.17.158

• Acetylene derivatives of 1,2,4-oxadiazoles, i.e., 5-(2-arylethynyl)-3-aryl-1,2,4-oxadiazoles, have been obtained, for the first time reported, from 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles by their bromination at the carbon–carbon double bond followed by di-dehydrobromination with NaNH2 in liquid NH3. The

• reaction of the acetylenyl-1,2,4-oxadiazoles with arenes in neat triflic acid TfOH (CF3SO3H) at room temperature for 1 h resulted in the formation of E/Z-5-(2,2-diarylethenyl)-3-aryl-1,2,4-oxadiazoles as products of regioselective hydroarylation of the acetylene bond. The addition of TfOH to the acetylene

• bond of these oxadiazoles quantitatively resulted in E/Z-vinyl triflates. The reactions of the cationic intermediates have been studied by DFT calculations and the reaction mechanisms are discussed. Keywords: acetylene-oxadiazoles; Friedel–Crafts reaction; hydroarylation; superelectrophilic activation

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• furylmercurials 91 via syn-addition of acetylene, which on carbonylation yielded the furan-containing carbonyl compound 92 (Scheme 30) [83]. It was proposed that initially mercuration of acetylene bonds via mercurinium like ions or π-complex takes place. Then the structure was stabilized through hydrogen bonding

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• to 2-bromoazulene (147) and subsequently to the TMS acetylene derivative 148 suitable for the ‘click’ reaction [46] to obtain the triazole 149, which was eventually transformed into the triazole-containing azulene methacrylate monomer 150 (Scheme 25B). The monomers 146 and 150 were then subjected to

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• obtain 2,3- and 2,3,6,7-halogenated anthracenes 26 by using CpCo(CO)2 as catalyst (Scheme 5) [39]. This synthesis started with a cobalt-catalyzed cyclotrimerization of previously prepared bis(propargyl)benzenes 22 and bis(trimethylsilyl)acetylene (23), affording the TMS-substituted cyclotrimerization

• ] cyclotrimerization reactions with bis(trimethylsilyl)acetylene (23). [2 + 2 + 2] Alkyne-cyclotrimerization reactions catalyzed by a CoCl2·6H2O/Zn reagent. Pd(II)-catalyzed sp3 C–H alkenylation of diphenyl carboxylic acids with acrylates. Pd(II)-catalyzed sp3 C–H arylation with o-tolualdehydes and aryl iodides

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• nucleoside 102 with N1-benzoyl-5-ethynyluracil followed by desilylation produced the double-headed nucleoside 104, whereas the reaction of the azido nucleoside 102 with trimethylsilylacetylene (TMS-acetylene) followed by desilylation produced the nucleoside 105 (Scheme 23) [14]. Christensen et al. [31

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Structural effects of meso-halogenation on porphyrins

• Keith J. Flanagan,
• Maximilian Paradiz Dominguez,
• Zoi Melissari,
• Hans-Georg Eckhardt,
• René M. Williams,
• Dáire Gibbons,
• Caroline Prior,
• Gemma M. Locke,
• Alina Meindl,
• Aoife A. Ryan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2021, 17, 1149–1170, doi:10.3762/bjoc.17.88

• obtained structures of the free base bromo derivative 1 and discuss the nickel(II) bromo derivative 2 [27] and the free base iodo derivative 3 [22] from the CSD [25]. Additionally, we have included the substituted derivative of 2 with an acetylene moiety (2A) to investigate the differences observed between

• large increase in the contribution of the B1u OOP mode. While the differences between halogen size and metal insertion are apparent, we were fortunate to obtain the structure of the acetylene-substituted derivative of compound 2 (2A). In this structure, we can look at the changes between 2A and its

• effects 5,10-di-halo-substitution that contain either a p-tolyl or 3,5-di-tert-butylphenyl group in the 15,20-positions (compounds 16–19) (Figure 19). The structure of compound 16A is a TMS-acetylene derivative of compound 16 which is included to analyze the difference in halogen and alternative

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• . Fullerene–acetylene derivatives 218 and 219 obtained by the tosylhydrazone method (Scheme 47) are also reported in the literature [164][165]. First, orthogonally protected diethinylmethanofullerene 216 was obtained and then converted to 217 by protodesilylation. Finally, blocks 218 and 219 were obtained by

• fullerene array 213. The synthetic route to conjugates 214 of fullerene with benzothiadiazole. The synthetic route to conjugates 215 of fullerene with diketopyrrolopyrrole. The synthetic route to fullerene–acetylene hybrids. [60]PCBM derivatives containing various aromatic and alkyl groups bound to the C60

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