Selective ring-opening metathesis polymerization (ROMP) of cyclobutenes. Unsymmetrical ladderphane containing polycyclobutene and polynorbornene strands

• Yuan-Zhen Ke,
• Shou-Ling Huang,
• Guoqiao Lai and
• Tien-Yau Luh

Beilstein J. Org. Chem. 2019, 15, 44–51, doi:10.3762/bjoc.15.4

• ]. Unsymmetrical polynorbornene-based ladderphane is obtained by a replication protocol from a single stranded polynorbornene [19][20]. Alternatively, sequential polymerization of a monomer containing a norbornene moiety and other polymerizable group furnishes an unsymmetrical ladderphane having two structurally

• monomer 9 (Scheme 4). Synthesis of unsymmetrical ladderphane 8 by sequential ROMPs catalyzed by 6 Polymerization of monomer 9 in the presence of 10 mol % of 6 was performed in THF at 0 °C for 4 h, followed by quenching with ethyl vinyl ether to give polymer 14 in 86% yield (Scheme 5). It is worth noting

• first polymerization. These observations are consistent with the results of our preliminary studies that only the cyclobutene moiety, but not norbornene in 9, proceeds 6-catalyzed ROMP under these conditions. The degree of polymerization of 14 was estimated to be 10 based on the 1H NMR integration of

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• intermediates [4][5][6]. Various types of reactions have been studied successfully by ESIMS ranging from Ziegler–Natta polymerization [7] and coupling reactions [8][9] to organic reactions such as the Baylis–Hillman [10][11][12][13][14][15], aldol [16][17][18] or Diels–Alder reactions [19][20]. An advantageous

New standards for collecting and fitting steady state kinetic data

• Kenneth A. Johnson

Beilstein J. Org. Chem. 2019, 15, 16–29, doi:10.3762/bjoc.15.2

• . Free energy profile for DNA polymerization. Free energy profiles for a correct base pair (solid blue line) and a mismatch (dashed green line) were computed from data presented in [21]. Summary of fitted parameters. Synthetic data were generated as described in the text and then fit to derive estimates

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• ). Importantly, later on Grubbs and co-workers utilized this kind of catalysts, featuring a chelating N-to-Ru arm, for the preparation of cyclic polymers from cyclic monomers via a ring-expansion metathesis polymerization (REMP) process [38][39]. With the aim of developing catalysts suitable for covalent

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• medicinal chemistry and biology [19][20], illustrated by the marketed drugs, e.g., alpidem, minodronic acid, olprinone, zolimidine (Figure 1) and some recent examples of the imidazopyridines inhibiting tubulin polymerization [21], NF-κB [22], aldosterone synthase [23], or autotaxin [24]. Whereas many

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• functionalities [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. This concept has also been of particular importance in the field of polymer science, known as reversible addition–fragmentation chain transfer (RAFT) polymerization [15][16]. Mechanistically, the degenerative transfer of xanthates 1 to olefins 2

• absorption [28][29][30][31][32][33][34][35][36][37]. In the area of polymer synthesis, visible-light-induced RAFT polymerization of xanthates with vinyl monomers under blue LED (light-emitting diode) irradiation has been reported [38][39][40][41]. Visible-light-induced single unit monomer insertion of the

• thiocarbonylthio compounds has also been developed for the synthesis of the sequence-controlled oligomers [41][42][43][44][45]. For example, the group of Boyer and Xu developed fac-Ir(ppy)3 (6)-catalyzed polymerization of xanthate 4 with various vinyl monomers such as vinyl acetate, providing polymers of type 5

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• chemistry. Thanks to the development of photoredox catalysts of polymerization, a drastic reduction of the amount of photoinitiators could be achieved, addressing the toxicity and the extractability issues; high performance initiating abilities are still obtained due to the catalytic approach which

• light exposure. These photochemical processes offer potential advantages compared to thermal polymerization. First, it is a greener technology, i.e., the system does not need to be heated and no (or low content of) volatile organic compounds are released. Secondly, mild conditions can be employed. It is

• : these processes are usually slow, expensive by requiring high temperature and high energy and release solvent (VOC). As an alternative of thermal polymerizations, polymerization upon light irradiation offers a good alternative. In both cases, polymerization occurs by the action of an initiating system

Nucleofugal behavior of a β-shielded α-cyanovinyl carbanion

• Rudolf Knorr and
• Barbara Schmidt

Beilstein J. Org. Chem. 2018, 14, 3018–3024, doi:10.3762/bjoc.14.281

• Rudolf Knorr Barbara Schmidt Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5–13 (Haus F), 81377 München, Germany 10.3762/bjoc.14.281 Abstract Sterically well-shielded against unsolicited Michael addition and polymerization reactions, α-metalated α-(1,1,3,3

A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts

• Daniel S. Müller,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2018, 14, 2999–3010, doi:10.3762/bjoc.14.279

• Blechert modification (Ru-6) initiates much faster with (E)-2-hexenyl acetate compared to the parent catalyst Ru-3. 4 Selected applications The synthetic usefulness of ruthenium dithiolate catalysts was demonstrated in numerous synthetic applications such as ring-opening metathesis polymerization (ROMP

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• metathesis constitutes the rearrangement of C=C double bonds in the presence of transition metal catalysts based on V, Mo, W, Re, Ru, and Os together with alkylating co-catalysts. This transformation is widely used in organic synthesis as well as in polymerization of various unsaturated monomers [1

• , and Ru [1]. Initially, these complexes were considered to be sensitive towards air and moisture. Nevertheless, adding Ru, Os and Ir salts to an aqueous solution or emulsion of a norbornene derivative led to ring-opening metathesis polymerization to give the corresponding polymer [5][6]. Through

• catalyst and carbohydrate or small polyethylene glycol (PEG) groups were attached [11]. As another strategy to modify a protein surface with olefin metathesis, Isarov and Pokorski introduced a Grubbs 3rd generation catalyst on the surface of lysozyme and performed ring-opening metathesis polymerization

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• significant attention owing to their good biocompatibility and biodegradability [1][2][3][4]. These attractive features allow them to be applied in medical and ecological materials as well as in commodity materials. The conventional way of synthesizing polyesters is the step-growth polymerization of diacids

• . However, there are some burdensome requisites, such as a precise stoichiometric balance between the carboxy and hydroxy groups and an efficient removal of small molecule byproducts, for the high conversion. Another conventional method for polyester synthesis is the chain-growth ring-opening polymerization

• (ROP) of lactones and cyclic diesters [5][6][7][8][9][10]. In contrast to the step-growth polymerization, the ROP does not give any small molecule byproducts and proceeds under mild conditions. In addition, high molecular weight polyesters with narrow polydispersity can be prepared even at a low

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• sulfonated polynaphthalene can be achieved in two steps: (a) polymerization of naphthalene (119) in nitrobenzene using FeCl3 as reagent (b) sulfonation of polynaphthalene (120) with chlorosulfonic acid in dichloromethane (Scheme 22). Amidoalkylnaphthol derivatives 50 were synthesized using catalyst 121 under

Comparative cell biological study of in vitro antitumor and antimetastatic activity on melanoma cells of GnRH-III-containing conjugates modified with short-chain fatty acids

• Eszter Lajkó,
• Sarah Spring,
• Rózsa Hegedüs,
• Beáta Biri-Kovács,
• Sven Ingebrandt,
• Gábor Mező and
• László Kőhidai

Beilstein J. Org. Chem. 2018, 14, 2495–2509, doi:10.3762/bjoc.14.226

• (i) expression of cell adhesion molecules (e.g., α3 integrin [25], non-integrin laminin receptor [56]) and (ii) regulate the actin polymerization by interacting with small GTPases (e.g., Rac1, CdC24 [54]) or (iii) interfere with the expression/activity of matrix-degrading enzymes (e.g., MMP-2 [25

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

• , living ring-opening alkyne metathesis polymerization (ROAMP) has been intensely studied for different molybdenum alkylidyne complexes by the group of F. R. Fischer, who was able to monitor the influence of both the alkylidyne moiety as well as the ancillary ligands [44][45][46][47][48]. More recently, we

• leads to polymerization initiated by intermediate deprotiometallacyclobutadiene species [55][60][61][65][66][67]. Moreover, the bimetallic [(t-BuO)3W≡W(Ot-Bu)3] complex has not been directly employed in catalytic alkyne metathesis. A. Mortreux and his group found that the alkyne metathesis selectivity

Nucleoside macrocycles formed by intramolecular click reaction: efficient cyclization of pyrimidine nucleosides decorated with 5'-azido residues and 5-octadiynyl side chains

• Jiang Liu,
• Peter Leonard,
• Sebastian L. Müller,
• Constantin Daniliuc and
• Frank Seela

Beilstein J. Org. Chem. 2018, 14, 2404–2410, doi:10.3762/bjoc.14.217

• . Conclusion The synthesis of a macrocycle is often described as an intramolecular cyclization of a bifunctional precursor molecule. However, in many cases competition exists with dimerization and polymerization. Therefore, we were delighted to see that the intramolecular cyclization, utilizing dU and dC

Hypervalent iodine compounds for anti-Markovnikov-type iodo-oxyimidation of vinylarenes

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Mikhail A. Syroeshkin,
• Alexander A. Korlyukov,
• Pavel V. Dorovatovskii,
• Yan V. Zubavichus,
• Gennady I. Nikishin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2018, 14, 2146–2155, doi:10.3762/bjoc.14.188

• electrochemical synthesis [2], and as mediators of living polymerization [10][11]. In organic synthesis more stable types of N-oxyl radicals can be used as carbon-centered radical scavengers [12], oxidation catalysts, mainly for conversion of alcohols to carbonyl compounds [11][13][14][15][16][17]. Less stable

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• film hydration method. To identify an optimal calixarene–AEPCDA ratio a series of PDA vesicles containing 1, 5, 10, 50 mol % of 10b was prepared. Polymerization of AEPCDA–calixarene vesicles was performed under UV irradiation using 254 nm light in quartz cuvettes of 1 cm path length. The absorbance

• ). Vesicle preparation and polymerization procedure In a similar manner as described before [22], concentrated dichloromethane solutions of N-(2-aminoethyl)pentacosa-10,12-diynamide (AEPCDA) and the appropriate amounts of calixarene were mixed together and the organic solvent was removed by expulsion with N2

• solution was filtered through a 1.2 µm filter and kept at 4 °C for 12 h. Polymerization was carried out by irradiating the solutions with 254 nm UV light (1 mW/cm2) for 15 min under vigorous stirring in 10 mm quartz cuvettes, placed in a thermostat holder at 25 °C. Quantum chemical calculations Quantum

Direct electrochemical generation of organic carbonates by dehydrogenative coupling

• Tile Gieshoff,
• Vinh Trieu,
• Jan Heijl and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2018, 14, 1578–1582, doi:10.3762/bjoc.14.135

• mixed carbonates [33]. Electrolysis experiments were conducted in undivided 5 mL beaker-type cells. Initial studies with benzene as the aromatic compound in acetonitrile in the presence of the described methyl carbonate salt did not result in the desired organic carbonate. Polymerization of the benzene

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• activities were evaluated [102]. A molecular docking study has revealed that GRA interacts with ct-DNAs via hydrogen bonding interactions between the oxygen atoms of GRA and adenine bases of DNA and van der Waals interactions. Moreover, GRA significantly reduces the polymerization activity of DNA polymerase

On the design principles of peptide–drug conjugates for targeted drug delivery to the malignant tumor site

• Eirinaios I. Vrettos,
• Gábor Mező and
• Andreas G. Tzakos

Beilstein J. Org. Chem. 2018, 14, 930–954, doi:10.3762/bjoc.14.80

• kinases. Gemcitabine diphosphate (dFdCDP) and gemcitabine triphosphate (dFdCTP) are the active metabolites which inhibit processes required for DNA synthesis [91]. The incorporation of dFdCTP into DNA during polymerization, which causes DNA polymerases unable to proceed, is the major mechanism by which

• , promoting mitotic halt and consequently cell death [93]. The difference with other known drugs that act on microtubules (vinca alkaloids) is that paclitaxel does not induce the disassembly of microtubules but boosts the polymerization of tubulin [94]. Sites available in PTX for the formation of PDCs are

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• recycling. Polymeric nanoreactors were also used to perform ring-opening polymerization (ROP) in water. Nallani et al. reported on the enzymatic polymerization of lactones using CalB, which was immobilized in both the polymersome lumen and bi-layer [21]. Nanoreactors for ROP were prepared from polystyrene

• -polyisocyanopeptide (PS-PIAT) and CalB was incorporated within either the lumen or polymer membrane (Figure 5). ROP is usually performed in organic solvent so that hydrolysis reactions can be avoided [17]. However, when nanoreactors were used, polymerization proceeded efficiently in water and without formation of any

• encapsulated in the lumen of the polymersome Pickering emulsion (right). Adapted with permission from [79]. Cross-linked polymersomes with Cu(OTf)2 catalyst. Reprinted with permission from [15]. Schematic representation of enzymatic polymerization in polymersomes. (A) CALB in the aqueous compartment (B) CALB

Enzyme-free genetic copying of DNA and RNA sequences

• Marilyne Sosson and
• Clemens Richert

Beilstein J. Org. Chem. 2018, 14, 603–617, doi:10.3762/bjoc.14.47

• the presence of poly(U) as template [12]. Polymerization of nucleotides with in situ activation had also been attempted with the aid of montmorillonite, a clay mineral, but had led mostly to dimers and pyrophosphate [54]. For DNA, ligations starting from unactivated starting materials were known [10

• via untemplated polymerization of the nucleotides [63]. This was a welcome side reaction, as it helps to explain how RNA may have been formed and copied under prebiotic conditions. In fact, when oligomerization assays were performed with any of the four natural ribonucleotides, oligomers of mixed

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• 57, which were used to connect with site-directing ligands [89] (Scheme 9). As reactive intermediates, o-QMs can also play the role of monomers in polymerization reactions. Ishida et al. reported the ring-opening polymerization of monofunctional alkyl-substituted aromatic amine-based benzoxazines [90

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• photoredox-catalyzed radical thiol–ene reaction for polymer postfunctionalization and step-growth addition polymerization (Scheme 4a) [33]. In contrast to Yoon’s conditions, they used [Ru(bpy)3]Cl2 as photocatalyst and N-methyl-2-pyrrolidone as solvent and were able to efficiently couple polybutadiene and

• poly(allyl methacrylates) with a series of functionalized thiols. Step-growth addition polymerization for the preparation of linear polymers also was achieved using dithiols and dienes for the reaction. Recently, Chung and co-workers were successful in functionalizing natural lignin by applying Yoon’s

Acid-catalyzed ring-opening reactions of a cyclopropanated 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with alcohols

• Katrina Tait,
• Alysia Horvath,
• Nicolas Blanchard and
• William Tam

Beilstein J. Org. Chem. 2017, 13, 2888–2894, doi:10.3762/bjoc.13.281

• most cases, the starting material was completely consumed, the yields of these ring-opening reactions were only moderate (26–61%). This may be due to the decomposition or polymerization of the cyclopropanated 3-aza-2-oxabicyclic alkene under the reaction conditions. Through X-ray crystallography [20