Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• polymerization. Extensive optimization led us to a set of conditions that routinely provided 4-nitro[2.2]paracyclophane (4) in good yields regardless of the scale of reaction (nitration has been performed on scales ranging from 0.5 g to 30 g). The 1H NMR of the crude reaction mixture invariably shows two other

• . Reaction of 1 with nitric acid alone led to a surprisingly clean, nitration, albeit by a very slow reaction. As stated earlier, nitration is normally a messy reaction. Presumably, the low concentration of nitronium ion present in equilibrium with the acid promotes a clean reaction without polymerization or

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

• Cansu Esen and
• Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

• , ascorbic acid/hydrogen peroxide, respectively. The mixture was immediately placed in a Petri dish to complete the gelation via free radical polymerization under dark conditions. After 3 hours, the resulting hydrogel was purified with water to remove the unreacted species (monomers and redox mediators

• modification platform [49]. The as-prepared hydrogel network (HGCM) was immersed in various acrylic monomers. Following that, photoinduced free radical polymerization of employed monomers performed under visible light irradiation by taking advantage of embedded g-CN nanosheets in HGCM. According to literature

• , g-CN as an organic semiconductor is utilized in polymerization processes as a photoinitiator by generation of reactive radical species (O2−•, HO•, HO2•) under convenient light illumination. The ability of g-CN to initiate polymerization and act as a polymerization locus for a covalent polymer growth

Highly regio- and stereoselective phosphinylphosphination of terminal alkynes with tetraphenyldiphosphine monoxide under radical conditions

• Dat Phuc Tran,
• Yuki Sato,
• Yuki Yamamoto,
• Shin-ichi Kawaguchi,
• Shintaro Kodama,
• Akihiro Nomoto and
• Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 866–872, doi:10.3762/bjoc.17.72

• [38][42]. The ratio of V-40/2a was important to depress the formation of self-polymerization of 2a (Table 1, entries 5–7). The results showed that the best amount of V-40 toward 2a was 10 mol %. Besides, the side product 3a’ is found up to 8% yield under photoirradiation. Considering that in our

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

1,2,3-Triazoles as leaving groups: S_NAr reactions of 2,6-bistriazolylpurines with O- and C-nucleophiles

• Dace Cīrule,
• Irina Novosjolova,
• Ērika Bizdēna and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 410–419, doi:10.3762/bjoc.17.37

• deprotonated acetylacetone and diphenylmethane. Even there are reports on SNAr reactions of acetylacetone with purines and pyrimidines [56][80], in our hands only polymerization of acetylacetone was observed. On the other hand, the diphenylmethane anion (pKa 32; DMSO [81]) apparently is too basic and

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

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• ]. The radical ring-opening polymerization (RROP) provides a synthetic route to fluoropolymers, which are useful materials [91]. The RROP of gem-difluorovinylcyclopropane (90) gave mainly the polymer with an unsymmetrical repeating unit, by the cleavage of the C2–C3 bond in the ring (Scheme 44, path a

A sustainable strategy for the straightforward preparation of 2H-azirines and highly functionalized NH-aziridines from vinyl azides using a single solvent flow-batch approach

• Michael Andresini,
• Leonardo Degannaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2021, 17, 203–209, doi:10.3762/bjoc.17.20

• isolate 3-(perfluorophenyl)-2H-azirine (2k) due to its rapid polymerization in the crude mixture. Interestingly, aliphatic vinyl azides 1h–j were found less reactive, and the corresponding azirines 2h–j were obtained in just 74–77% yield, in mixtures with unreacted starting materials. However, when the

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• ultrahigh molecular weight (≈106 g⋅mol−1) and a reasonably low dispersity (Đ ≥ 1.33) by using various monomers. Triethanolamine (TEOA) was used as an electron donor to initiate the photoinduced electron transfer to the PDI–CB[7] system, and thus to start the polymerization reaction. In addition, the rate of

• macrocycle has inherent chromophores that can function as photosensitizers, the efficiency of the energy transfer will be higher and the systems will be simplified. 3) Other kinds of macrocycle-based catalysis need to be explored, such as esterification, polymerization, redox reaction, etc. 4) Hyperbranched

• supramolecular PDI–CB[7] complex and structures of monomers and the chain transfer agent. Republished with permission of The Royal Society of Chemistry from [48] (“Visible light induced aqueous RAFT polymerization using a supramolecular perylene diimide/cucurbit[7]uril complex” by Y. Yang et al., Polym. Chem

Supramolecular polymers with reversed viscosity/temperature profile for application in motor oils

• Jan-Erik Ostwaldt,
• Christoph Hirschhäuser,
• Stefan K. Maier,
• Carsten Schmuck and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2021, 17, 105–114, doi:10.3762/bjoc.17.11

• develop such novel VIIs, we envisaged the use of ditopic building blocks, which are able to reversibly form supramolecular polymers at higher temperatures. Supramolecular polymerization should increase the hydrodynamic radius and thus was expected to lead to increased viscosities [9]. There are different

• mechanisms for the formation of supramolecular polymers from molecular building blocks: The isodesmic, the cooperative and the ring–chain-mediated supramolecular polymerization [10]. For an application in viscosity improvement, a higher degree of polymerization is desired at elevated temperatures, which can

• be achieved by a ring–chain-based polymerization [11]. In this context, Sijbesma and Meijer reported an early example of a low-molecular weight VII using a ditopic monomer which undergoes supramolecular polymerization at elevated temperatures (Figure 1) [12][13]. The system consists of two self

Supramolecular polymerization of sulfated dendritic peptide amphiphiles into multivalent L-selectin binders

• David Straßburger,
• Svenja Herziger,
• Katharina Huth,
• Moritz Urschbach,
• Rainer Haag and
• Pol Besenius

Beilstein J. Org. Chem. 2021, 17, 97–104, doi:10.3762/bjoc.17.10

• ionic strength on the supramolecular polymerization was probed via circular dichroism spectroscopy and cryogenic transmission electron microscopy. Physiological salt concentrations efficiently screen the charges of the dendritic building block equipped with eight sulfate groups and trigger the formation

• , post-functionalization using a subsequent copper-catalyzed azide–alkyne cycloaddition reaction became accessible [35][36]. At the same time the other two unmodified side arms of the dendritic amphiphile make sure that the fidelity of the β-sheet motifs and directed supramolecular polymerization remains

• polymerization strongly relies on the formation of secondary structure elements, leading to ordered domains that lead to characteristic CD band spectra. By probing aqueous solutions of I at different concentrations in H2O, a strongly negative CD band at around λ ≈ 220 nm became apparent (Figure 1A). In the past

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• electroactive materials [52][53][54]. Carbazole-based [6]helicenes [42] and [7]helicenes [50] showed deep blue electroluminescence and have been investigated in OLED devices. Some carbazole-based [5]- and [6]helicenes have been used as visible light photoinitiators for cationic and radical polymerization [41

Amine–borane complex-initiated SF₅Cl radical addition on alkenes and alkynes

• Audrey Gilbert,
• Pauline Langowski,
• Marine Delgado,
• Laurent Chabaud,
• Mathieu Pucheault and
• Jean-François Paquin

Beilstein J. Org. Chem. 2020, 16, 3069–3077, doi:10.3762/bjoc.16.256

• recently, it has been shown that some of these common amine–borane complexes can also be used as radical initiators for atom transfer radical addition of alkyl halides to alkenes [48]. They were also used in the free-radical polymerization of alkene-containing monomers such as methyl methacrylate or

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• polymerization reaction between polydiacetylene. PDA liposomes turn colorless to red upon formation of cross-linked liposomes. The fluorescence of the naphthimide is completely quenched due to the energy transfer from the fluorophore to the cross-linked polymer. However, addition of LPS restores the fluorescence

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

• reactions of unsaturated compounds, e.g., alkene and enyne cross metathesis (CM [1] and EYCM [2][3][4]), alkene and enyne ring-closing metathesis (RCM and RCEYM) [5][6], ring-opening metathetic polymerization (ROMP) [7], etc., the CM and RCM are the most popular in organic synthesis [8]. Furthermore, the

• be too unstable and prone to polymerization. On the other hand, the reactivity of oxaenediyne 3 was too sluggish. Hence, 4-(allyloxy)hepta-1,6-diyne (2a) and its derivatives became the framework of choice. The key starting compound for the synthesis of oxaenediyne 2a and its derivatives was hepta-1,6

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• 27 in a single step. They also pointed out that when ethylene gas was used as an alkene source for the ring-opening step, diluted reaction conditions were necessary to dissolve the ethylene in dichloromethane to avoid polymerization. Therefore, after several experimentations, they noticed that liquid

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• sequence. On the other hand, the successful thermal iminium-ion induced SE(Ar) reactions shown in Scheme 2 were not applicable to the iminium-substituted norbornadiene 2, which suffered undefined polymerization on moderate heating in various solvents. In contrast to so far unknown 9‑amino-9

Three new O-isocrotonyl-3-hydroxybutyric acid congeners produced by a sea anemone-derived marine bacterium of the genus Vibrio

• Dandan Li,
• Enjuro Harunari,
• Tao Zhou,
• Naoya Oku and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1869–1874, doi:10.3762/bjoc.16.154

• )-configured 3-hydroxy fatty acids [13], and 3-hydroxybutyric acid in 3 and 4 and 3-hydroxyhexanoic acid in 2 are the most common two building blocks for PHAs [14]. However, degrees of polymerization as low as for 1–4 and the dehydrative modifications are unprecedented, besides for 5 [9]. Because PHAs are by

Synthesis, docking study and biological evaluation of ᴅ-fructofuranosyl and ᴅ-tagatofuranosyl sulfones as potential inhibitors of the mycobacterial galactan synthesis targeting the galactofuranosyltransferase GlfT2

• Marek Baráth,
• Jana Jakubčinová,
• Zuzana Konyariková,
• Stanislav Kozmon,
• Katarína Mikušová and
• Maroš Bella

Beilstein J. Org. Chem. 2020, 16, 1853–1862, doi:10.3762/bjoc.16.152

• decaprenyl-P-P-GlcNAc-Rha, (glycolipid 2, GL2), which serves as a lipid carrier for arabinogalactan polymerization [7][8]. The latter enzyme, GlfT2, extends the product of GlfT1-catalyzed reaction, decaprenyl-P-P-GlcNAc-Rha-Galf2 (glycolipid 4, GL4), producing the lipid-linked galactan polymer [8]. Both

• -up of lipid-linked galactan precursors. The crude enzymes used in the assay allow for in situ synthesis of the acceptor for galactan polymerization, decaprenyl-P-P-GlcNAc-Rha (GL2), from endogenous decaprenyl phosphate and sugar nucleotides UDP-GlcNAc and TDP-Rha supplied in the reaction mixture

One-pot synthesis of oxazolidinones and five-membered cyclic carbonates from epoxides and chlorosulfonyl isocyanate: theoretical evidence for an asynchronous concerted pathway

• Esra Demir,
• Ozlem Sari,
• Yasin Çetinkaya,
• Ufuk Atmaca,
• Safiye Sağ Erdem and
• Murat Çelik

Beilstein J. Org. Chem. 2020, 16, 1805–1819, doi:10.3762/bjoc.16.148

• polymerization of the compounds containing cyclic carbonates such as methyl 4,6-O-benzylidene-2,3-O-carbonyl-α-ᴅ-glucopyranoside (MBCG) (5) [19][20] and glycerol carbonate (6) [21] were also reported (Scheme 1). Therefore, numerous synthetic approaches have been developed to date for the preparation of

Mechanochemical green synthesis of hyper-crosslinked cyclodextrin polymers

• Alberto Rubin Pedrazzo,
• Fabrizio Caldera,
• Marco Zanetti,
• Silvia Lucia Appleton,
• Nilesh Kumar Dhakar and
• Francesco Trotta

Beilstein J. Org. Chem. 2020, 16, 1554–1563, doi:10.3762/bjoc.16.127

• catalyst, if necessary. The solvents of choice were usually organic polar aprotic liquids, for example, N,N-dimethylformamide or dimethyl sulfoxide (DMSO). An alternative synthetic route relied on interfacial polymerization, where two immiscible solutions, one consisting of CDs dissolved in an alkaline

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• used in the development of organic magnetic materials [1], organic batteries [2][3][4], in the preparation of polymers by living polymerization [5][6], in the studies of biomolecules and living systems by EPR [7] and NMR [8] techniques. Stable N-oxyl radicals occupy a central place in organic chemistry

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

• . Poly(propiolate) salts are formed by polymerization of the starting materials after heating. The different cations of the propiolates cause changes in the thermal behavior of the starting materials since different temperatures are required for the decomposition or different amounts of gases are

• structures in the carbon source [6]. Diamadopoulos and co-workers observed also the production of smaller surface areas by H3PO4 activation of bagasse and rice husk due to a reaction of the activating reagent with the carbon precursor. Thereby, phosphate esters or polymerization byproducts are formed, which

• conform to the LaMer model and starts with a polymerization step of the carbohydrate monomers and followed by a carbonization step when the nucleation is caused by the supersaturation of the solution. The resulting nuclei grow uniformly until the final size is obtained depending on the growth parameters

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

Synthesis of esters of diaminotruxillic bis-amino acids by Pd-mediated photocycloaddition of analogs of the Kaede protein chromophore

• Esteban P. Urriolabeitia,
• Pablo Sánchez,
• Alexandra Pop,
• Cristian Silvestru,
• Eduardo Laga,
• Ana I. Jiménez and
• Carlos Cativiela

Beilstein J. Org. Chem. 2020, 16, 1111–1123, doi:10.3762/bjoc.16.98

• applications as internal donors in Ziegler–Natta catalysts for polymerization [14] or as building blocks in polymer chemistry [15]. A very closely related group of cyclobutanes are the 1,3-diaminotruxillic ester derivatives (Figure 1b). This type of bis-amino esters also shows remarkable pharmacological