Unveiling the regioselectivity of rhodium(I)-catalyzed [2 + 2 + 2] cycloaddition reactions for open-cage C₇₀ production

• Cristina Castanyer,
• Anna Pla-Quintana,
• Anna Roglans,
• Albert Artigas and
• Miquel Solà

Beilstein J. Org. Chem. 2024, 20, 272–279, doi:10.3762/bjoc.20.28

• holds significant promise for applications in the fields of medicinal chemistry, materials science, and photovoltaics. In this study, we investigate the regioselectivity of the rhodium(I)-catalyzed [2 + 2 + 2] cycloaddition reactions between diynes and C70 as a novel procedure for generating C70 bis

• reaction between diynes and C60, followed by a cage-opening through a Rh‐catalyzed di‐π‐methane rearrangement (Scheme 1). It is well-known that [6,6]-bonds (the bonds at the junction between two six-membered rings, Figure 1, left) are more reactive than [5,6]-bonds in C60 [36][37][38], and, not

• explore, both experimentally and computationally, the Rh-catalyzed intermolecular [2 + 2 + 2] cycloaddition reaction between diynes and C70 as a new procedure to generate C70 bis(fulleroids). We are particularly interested in the analysis of the regioselectivity of this [2 + 2 + 2] cycloaddition. Results

Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• of bisanilino-end-capped buta-1,3-diynes with TCNE, simultaneous [2 + 2] CA–RE reactions proceed for each of the two alkyne moieties of the buta-1,3-diyne skeletons, forming octacyano[4]dendralene molecules corresponding to TCBD dimers [87][88]. A well-recognized potent electron acceptor, 2,3

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• , including naphthalene cores, butadiyne and acetylene linkers. The main structural parameters of diynes 5 that characterize the degree of this distortion are presented in Table 2, where ϕ1 is the angle between the planes of the benzene ring and the neighboring naphthalene system, ϕ2 is the angle between the

• formally symmetrical structure of diynes 5, naphthalene rings A and B of molecules 5b and 5d differ in their structural parameters. At the same time, the monomer fragments of the nitro derivative 5e are identical. In the case of 5e, the naphthalene rings lie in parallel planes, while in crystals of 5b and

• noticeable difference in the absorption maxima of diynes 5a–c and the corresponding monomers 6a–c. Moreover, the absorption maxima of compounds 5a (R = H), 5b (R = OMe), and 5c (R = CF3) are rather close to diyne 1. Figure 8 clearly demonstrates that in these cases the profiles of the long-wavelength maximum

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

• of Cu(I). As an alternative route, we also surmise that Cu–acetylide E attacks intermediate A to produce intermediate D. Although this reaction was performed under aerobic conditions, Glaser-type homocoupling of terminal alkynes did not occur, and no diynes were observed as byproducts. Moreover, the

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• -forming reaction [74]. As a notable exception, in 2016, Hwang’s group [75] reported the novel synthesis of unsymmetrical 1,3-conjugated diynes 31 from terminal alkynes under LED irradiation. The reaction mechanism involved a bipolar heterodimeric copper phenylacetylide species that showed similar

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

• -cyclotrimerization reaction catalyzed by a cobalt/zinc reagent [40]. With regard to substituted anthracenes, this method consisted of a [2 + 2 + 2] cycloaddition reaction of 1,6-diynes 27 with 4-aryl-2-butyn-1-ols 28 (Scheme 6). The authors converted the resulting benzylic alcohols 29 to the corresponding aldehydes

Ring-closing metathesis of prochiral oxaenediynes to racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans

• Viola Kolaříková,
• Markéta Rybáčková,
• Martin Svoboda and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2020, 16, 2757–2768, doi:10.3762/bjoc.16.226

• ., Flemingovo nám. 2, 166 10 Prague 6, Czech Republic 10.3762/bjoc.16.226 Abstract The prochiral 4-(allyloxy)hepta-1,6-diynes, optionally modified in the positions 1 and 7 with an alkyl or ester group, undergo a chemoselective ring-closing enyne metathesis yielding racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H

Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts

• Faïma Lazreg,
• Marie Vasseur,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2020, 16, 482–491, doi:10.3762/bjoc.16.43

• substrate, solvent-free conditions lead to 78% isolated yield at 40 °C. Diynes were also investigated and excellent isolated yields were achieved (92% and 85% for 11j and 11k, respectively). Regarding the alkyl-alkynes, longer reactions times as well as higher temperature were required to reach high

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

• of conjugated diynes (DYCM) is promoted by the benzylidyne tungsten complex II with silanolate ligands (X = OSi(Ot-Bu)3) [21][22]; this catalyst is also active in classical alkyne metathesis [23]. Complex III with chelating phenoxide ligands [24][25][26][27] is mostly applied in supramolecular

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles

• Takashi Go,
• Akane Morimatsu,
• Hiroaki Wasada,
• Genzoh Tanabe,
• Osamu Muraoka,
• Yoshiharu Sawada and
• Mitsuhiro Yoshimatsu

Beilstein J. Org. Chem. 2018, 14, 2722–2729, doi:10.3762/bjoc.14.250

• -diynes with secondary amines resulted in the formation of 3-sulfanylmethyl-4-aminomethylpyrroles (Scheme 1) [32][33]. The sulfanyl group of pyrroles is easily oxidised to produce their corresponding sulfoxides. When we performed the Pummerer reaction and cyclization of pyrrolesulfoxides to obtain their

• -bromobenzenesulfonyl derivative, which was expected to act as a good substrate for the isolation of crystals, and performed the same sequential process of sulfanyl-1,6-diynes to the oxazine derivatives (Scheme 7). Hydroamination–cyclisation of diyne 1 with N-allyl-p-bromobenzenesulfonamide 3g and the successive

• 1,7-Se shift reactions by investigating the synthesis of pyrroloazepines through amination–cyclisation of 1,6-diynes, followed by the Pummerer reaction and TBAH hydrolysis. We are now investigating the syntheses of pyrroloazepines using 4-heteroarylmethyl-3-sulfanylpyrroles, which could be easily

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• [2 + 2 + 2] cycloaddition of diynes and CO2 proceeds to afford pyrones. Keywords: carbon dioxide; carboxylation; cobalt; homogeneous catalysts; rhodium; Introduction Carbon dioxide (CO2) is one of the most important materials as renewable feedstock [1][2][3][4]. However, the thermodynamic and

• hydrocarboxylation of styrene derivatives has been achieved. Furthermore, the formation of pyrones from diynes and CO2 can be effectively catalyzed by Rh complexes. Review Cobalt catalysts Carboxylation of propargyl acetates Allyl and propargyl electrophiles, such as halides and esters, are well known as efficient

• (Scheme 38). [2 + 2 + 2] Cycloaddition of diynes with CO2 The [2 + 2 + 2] cycloaddition of diynes with CO2 is an important reaction in the field of CO2 fixation. In these reactions, cyclic esters such as pyrones can be obtained, which are classically catalyzed by Ni complexes [76][77][78]. Tanaka et al

Efficient catalytic alkyne metathesis with a fluoroalkoxy-supported ditungsten(III) complex

• Henrike Ehrhorn,
• Janin Schlösser,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2018, 14, 2425–2434, doi:10.3762/bjoc.14.220

• triphenylsiloxide ligands (type II) introduced by A. Fürstner and co–workers is frequently used in the total synthesis of natural products [23][24][25][26][27]. A unique catalytic reactivity towards conjugated diynes was observed for the tungsten benzylidyne complex with OSi(Ot-Bu)3 ligands (type III) [28][29][30

• and terminal alkynes and diynes”). The authors wish to thank Dr. M. Freytag for the crystal structure determination of W2F3·(NHMe2).

Stereoselective total synthesis and structural revision of the diacetylenic diol natural products strongylodiols H and I

• Pamarthi Gangadhar,
• Sayini Ramakrishna,
• Ponneri Venkateswarlu and
• Pabbaraja Srihari

Beilstein J. Org. Chem. 2018, 14, 2313–2320, doi:10.3762/bjoc.14.206

• alkyne 19 provided the corresponding diynes 25 and 25a in a 1:1 ratio. Though we had an option to proceed further with the mixture of 25 and 25a affording both enantiomers that could be separated later, we focused our attention towards the synthesis of the required chiral compound. Thus, the mixture of

Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds

• M. Fernanda N. N. Carvalho,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2017, 13, 1230–1238, doi:10.3762/bjoc.13.122

• ], occasionally accompanied by a Wagner–Meerwein rearrangement [23]. However, no such products were found with any of the diynes 4. Our first attempts to employ 4a as a ligand with Ti(IV) resulted, somewhat surprisingly, in the addition of HCl under simultaneous annulation (three-carbon expansion [24][25]) of a

• depend on the nature of the substituents at the alkyne groups, it would be of interest to explore the course of the reaction when the two substituents are different. In this article, we develop reasonable synthetic procedures for the starting diynes, and present the first result of a catalytic Pt(II

• ) reaction of such mixed substituted compounds. Results and Discussion For the preparation of the diynes 4, a 2:1 ratio (or slightly larger for complete reaction) of the lithium salt of a terminal alkyne and of the oxoimide 3 is applied. The ratio should, however, not be increased too much. For instance

Stereodynamic tetrahydrobiisoindole “NU-BIPHEP(O)”s: functionalization, rotational barriers and non-covalent interactions

• Golo Storch,
• Sebastian Pallmann,
• Frank Rominger and
• Oliver Trapp

Beilstein J. Org. Chem. 2016, 12, 1453–1458, doi:10.3762/bjoc.12.141

• preparation of “NU-BIPHEPs” [23] and related biaryls [24]. Doherty et al. reported the use of various diynes yielding for instance tetrahydrobiindene 1a and N-tosyl-protected tetrahydrobiisoindole 1b as the only N-heterocyclic compound (Figure 1A). Aiming at facile deprotection and enabling subsequent

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• deuterium kinetic isotope effect of 2.34 was seen for C–H insertion with gold catalysis. Hashmi demonstrated the viability of dual gold catalysis for carbene/alkyne cascades with diynes like 109, which gave products from either a 1,2-methyl shift (not shown) or a C–H bond insertion to form enone 112 (Scheme

Asymmetric 1,4-bis(ethynyl)bicyclo[2.2.2]octane rotators via monocarbinol functionalization. Ready access to polyrotors

• Cyprien Lemouchi and
• Patrick Batail

Beilstein J. Org. Chem. 2015, 11, 1881–1885, doi:10.3762/bjoc.11.202

• scale. These limitations are lifted by our novel strategy. Hence, 5 is obtained in a better yield and a higher purity. Besides, this novel approach delivers the monosubstituted BCOs 1 and 8 and, in turn, the alcohol and carboxylate-functionalized dirotor diynes, 3 and 9. It is important to note that 8

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• -workers [96] demonstrated a macrocylization, with an inbuilt conformation control element to form rigid cyclophanes through the Glaser–Hay coupling. In this regard, diynes 59a–c were treated with CuCl2 and TMEDA in the presence of oxygen to afford the cyclized products 61a–c (Scheme 9). Intramolecular

• differently substituted diynes 120a–c. Deprotection of silyl groups in 120a–c using TBAF furnished the key intermediates 121a–c in moderate to good yields. Treatment of 121a–c with Pd(PPh3)4 and copper iodide in THF in the presence of diisopropylamine gave the desired macrocycles 122a–c (Scheme 17). Suzuki

• applicable to synthesize various polyether-based cyclophanes. In this report, they have synthesized various polyether containing cyclophanes by a cross-cyclotrimerization catalyzed by a cationic rhodium(I)/H8-BINAP complex as a key step. The ether linked α,ω-diynes and dimethyl acetylenedicarboxylate were

Synthesis of antibacterial 1,3-diyne-linked peptoids from an Ugi-4CR/Glaser coupling approach

• Martin C. N. Brauer,
• Ricardo A. W. Neves Filho,
• Bernhard Westermann,
• Ramona Heinke and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2015, 11, 25–30, doi:10.3762/bjoc.11.4

• -libraries of homo- and heterodimers verified by ESI-MS and HPLC. In a preliminary evaluation, some compounds display moderate activity against the Gram-positive bacterium Bacillus subtilis. Keywords: antibacterial; combinatorial; diynes; homodimerization; multicomponent reactions; peptoids; Ugi reaction

• -diynes because it does not require expensive catalysts, ligands, or additives (Table 1) [34]. The coupling reaction was clean without notable side product formation as confirmed by TLC analysis, and the desired peptoid dimers 8a–j could be obtained in high to quantitative yields. Aromatic as well as

Copper-promoted hydration and annulation of 2-fluorophenylacetylene derivatives: from alkynes to benzo[b]furans and benzo[b]thiophenes

• Yibiao Li,
• Liang Cheng,
• Xiaohang Liu,
• Bin Li and
• Ning Sun

Beilstein J. Org. Chem. 2014, 10, 2886–2891, doi:10.3762/bjoc.10.305

• annulation of 1,3-diynes, which have great synthetic potential in medicine and materials sciences [38][39][40]. For extensions, we used 1,4-bis(2-fluorophenyl)buta-1,3-diyne as a substrate to investigate the possibility of this transformation. Similar to (2-(2-fluorophenyl)ethynyl)benzene, 1,4-bis(2

Selenium halide-induced bridge formation in [2.2]paracyclophanes

• Laura G. Sarbu,
• Henning Hopf,
• Peter G. Jones and
• Lucian M. Birsa

Beilstein J. Org. Chem. 2014, 10, 2550–2555, doi:10.3762/bjoc.10.266

• substructure. The reactions have been found to be sensitive to the substitution of the ethynyl group. The formation of dienes with a zig-zag configuration is related to that observed for non-conjugated cyclic diynes of medium ring size. Keywords: acetylenes; dienes; [2.2]paracyclophane; selenium halides

• synthetic procedure involves an addition/elimination protocol of selenium derivatives, the formation of isomeric endo-exo-dienes 2, 3 and 5, 6 resembles the zig-zag cyclizations of nonconjugated cyclic diynes of medium ring size reported by Gleiter [31][32]. In order to check the limits of these selenium

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• (I) oxidation state in aqueous solution [14][64]. This is important as Cu(II) ions are harmful to this experiment in two ways: on the one hand, Cu(II) ions catalyze the oxidative coupling of the alkyne substrates to give diynes as undesired byproducts (Glaser coupling [9][10][11], Eglinton coupling

Flexible synthesis of anthracycline aglycone mimics via domino carbopalladation reactions

• Markus Leibeling and
• Daniel B. Werz

Beilstein J. Org. Chem. 2013, 9, 2194–2201, doi:10.3762/bjoc.9.258

• envisioned. Respective silyl-substituted diynes 16 can be traced back to phthalide (17). To differentiate between the insertion of two differently substituted silylacetylenes, the lactone 17 had to be first converted into a monoprotected diol for further transformations. Synthesis of dialkyne building blocks

Gold(I)-catalyzed formation of furans from γ-acyloxyalkynyl ketones

• Marie Hoffmann,
• Solène Miaskiewicz,
• Jean-Marc Weibel,
• Patrick Pale and
• Aurélien Blanc

Beilstein J. Org. Chem. 2013, 9, 1774–1780, doi:10.3762/bjoc.9.206

• catalysts with their carbophilic character have emerged as a new tool for furan preparation. As summarized in Scheme 1, furans could now be obtained by either gold(I) or gold(III) catalysis from various types of substrates such as allenyl ketones [8][9][10][11][12][13][14], enynes or diynes [15][16][17