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

• loading of 0.125 mol %. In 2008, Blechert and Buchmeiser et al. introduced a ruthenium complex featuring an unsymmetrical, chiral NHC ligand 44 and its pyridine derivative 45 (Figure 12) [26]. Both complexes revealed as efficient systems to promote the alternating copolymerization of norbornene (NBE, 46

• catalysts 61, 64, 65, 67 and 68 (Figure 16) were also investigated in the model asymmetric ring-opening cross metathesis (AROCM) of cis-5-norbornene-endo-2,3-dicarboxylic anhydride (75) with styrene (Scheme 8, Table 3) [32]. In this reaction complex 68 showed the highest selectivity for the formation of the

• -hexene, giving no conversion at room temperature and dimerization at 85 °C. Exchanging the chloride ligands for iodide ligands led to catalysts 80 and 82 with superior latent behavior that allowed for the latent ROMP of norbornene derivatives (e.g., 83, Scheme 9). In order to improve the selectivities in

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

• (Table 2, entry 11), implicating that the redox process is partially operating along with the main radical chain process. Norbornene (2m) was found reactive for degenerative transfer of xanthate 1a (Table 2, entry 12). The reaction was also applied to dienes 2n and 2o, which led the formation of

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

• (Scheme 2a). Both catalysts Ru-1 and Ru-2 achieved excellent selectivities and good yields for the ROMP of norbornene (1) with catalyst loadings as low as 20 ppm (Scheme 2a) [2]. The ROMP of cyclooctadiene 3 was equally efficient with catalysts Ru-1 and Ru-2 [2]. It should be noted that the ROMP of

• norbornadiene was also investigated by Hoveyda [16]. A highly syndiotactic polymer was obtained by fine tuning of the steric and electronic characteristics of the catalyst (not depicted in this review) [16]. ROCM reactions of norbornene (1) with styrene (5) could be carried out with only one mole percent of

• catalyst loading Scheme 2b) [2]. Allylic alcohol (7) reacted cleanly with norbornene (1), albeit with lower stereoretention (8; 88:12 Z/E) [17]. Cyclobutenes (e.g., 9) and cyclopropenes also delivered the corresponding products with good yields and excellent selectivity (Scheme 2b) [17]. It should also be

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

• , 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

• (ROMP) on the protein surface employing a PEGylated norbornene derivative as substrate [13]. This led to proteins modified with PEG chains. These two examples illustrate the potential applications of olefin metathesis in protein modification. Further applications would be the implementation of olefin

• was subjected to conjugation of catalysts Ru-4/5/6. Indeed, all catalysts underwent covalent anchoring with high conjugational yield (confirmed via ICP–OES and ESIMS) [62]. Upon catalysis, Ru-5@NB4exp as well as Ru-6@NB4exp showed high activity in the ROMP of norbornene 7 with TONs up to 10,000. For

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

• Ritabrata Datta Subrata Ghosh School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India 10.3762/bjoc.14.248 Abstract The metathesis of norbornene derivatives with alkynyl side-chain with Grubbs’ ruthenium alkylidine as catalyst has been

• investigated with the objective of constructing condensed polycyclic structures. This investigation demonstrated that the generally observed domino reaction course involving a ring-opening metathesis of the norbornene unit and a ring-closing enyne metathesis is influenced to a great extent by the nature of the

• metathesis; natural products; polycarbocycles; Introduction The metathesis of norbornene derivatives having an alkene side-chain on the norbornene nucleus with Grubbs’ ruthenium catalysts has been extensively investigated. Generally the reaction proceeds through a domino process involving a ring opening of

Design and synthesis of C₃-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

• Sambasivarao Kotha,
• Saidulu Todeti and
• Vikas R. Aswar

Beilstein J. Org. Chem. 2018, 14, 2537–2544, doi:10.3762/bjoc.14.230

• product 11 (64%). Having the trimerized product 11, we attempted to open the norbornene system due to the fact that not all norbornene rings open up during RCM to generate propellane derivative. After allylation, RCM is not a clean reaction and it gave a mixture of the C3-symmetrical compounds. Therefore

• it is desirable to open the norbornene double bond before the trimerization sequence. To this end, the trimerized product 11 was treated with Grubbs first generation (G-I) catalyst in CH2Cl2 under ethylene atmosphere but, we were unable to get the ring-opened product 12 (Scheme 1). Later, we

• considered an alternate route to synthesize compound 12. In this regard, we employed different ruthenium-based catalysts (Figure 2) and reaction conditions to obtain the ring-opening metathesis (ROM) product 13 from norbornene derivate 10. Under these conditions the starting material was not consumed

Continuous-flow retro-Diels–Alder reaction: an efficient method for the preparation of pyrimidinone derivatives

• Imane Nekkaa,
• Márta Palkó,
• István M. Mándity and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2018, 14, 318–324, doi:10.3762/bjoc.14.20

• confirm the viability of preparing the desired pyrimidinones in short reaction times. Yields typically higher than those published earlier using conventional batch or microwave processes were achieved. Keywords: continuous-flow; desulfurisation; norbornene-fused heterocycles; pyrimidinones; retro-Diels

• di-exo- or di-endo-amino acids or esters with ethyl p-chlorobenzimidate resulted in tricyclic pyrimidinones 1, 2a and 2b [26][45][46][47][48][49]. Methanopyrrolo-, methanopyrido- and methanoazepino[2,1-b]quinazolinones 3–6 were prepared by ring enlargement of di-exo-norbornene-fused azetidinones with

Synthetic mRNA capping

• Fabian Muttach,
• Nils Muthmann and
• Andrea Rentmeister

Beilstein J. Org. Chem. 2017, 13, 2819–2832, doi:10.3762/bjoc.13.274

• ]. Recently, we revealed that the N7-cap methyltransferase Ecm1 from Encephalitozoon cuniculi is highly promiscuous. Sterically very demanding AdoMet analogues bearing for example a norbornene or 4-vinylbenzyl moiety were efficiently converted [92][93]. The pronounced promiscuity can be attributed to the

Mechanochemical N-alkylation of imides

• Anamarija Briš,
• Mateja Đud and
• Davor Margetić

Beilstein J. Org. Chem. 2017, 13, 1745–1752, doi:10.3762/bjoc.13.169

• Discussion The reaction of the norbornene endo-succinimide 1 [25] with 1,3-dibromopropane (2) was used as a model system for the optimization of the reaction conditions [26]. Here, imide 1 is a solid, while dibromopropane is a liquid reagent. It was found that during the ball-milling process (Retsch MM400

Bridgehead vicinal diallylation of norbornene derivatives and extension to propellane derivatives via ring-closing metathesis

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2016, 12, 1877–1883, doi:10.3762/bjoc.12.177

• Sambasivarao Kotha Rama Gunta Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai, India 10.3762/bjoc.12.177 Abstract Here, we report a simple synthetic strategy to the bridgehead vicinal diallylation of norbornene derivatives. These substrates are useful to generate

• propellanes via ring-closing metathesis. Single-crystal X-ray diffraction analysis of four compounds led to the realization of configurational correction of earlier reported molecules. Keywords: norbornene; propellane derivatives; ring-closing metathesis; single-crystal X-ray diffraction; vicinal

• diallylation; Introduction The norbornene moiety is a useful template and also a versatile synthon in organic synthesis [1]. The double bond present in the norbornene frame is strained and therefore participates in cycloaddition sequences as a C2-synthon [2][3]. It was reported that the norbornene system is

Recent advances in metathesis-derived polymers containing transition metals in the side chain

• Ileana Dragutan,
• Valerian Dragutan,
• Bogdan C. Simionescu,
• Albert Demonceau and
• Helmut Fischer

Beilstein J. Org. Chem. 2015, 11, 2747–2762, doi:10.3762/bjoc.11.296

• important for the polymer properties. They found that polymer 6 was soluble in water and various organic solvents when the counteranion was chloride. Subsequently, these authors copolymerized 6 with norbornene-2-carboxylic acid, using Grubbs 3rd generation catalyst, to prepare diblock copolymer 7, in which

• application of metallopolymers as heterogeneous macromolecular catalysts for living radical polymerizations, Tang et al. [51] produced the cobalt-containing polymer 10 by ROMP of the norbornene monomer 9, derivatized with triazolyl and cyclopentadienylcobalt-1,3-cyclopentadiene moieties (Scheme 5). The

• triazolyl unit was first attached to the η4-cyclopentadiene CpCo(I) complex by click reaction of the corresponding alkyne precursor and then the triazolyl-Co scaffold was incorporated into the norbornene monomer 9 by conventional esterification. It is important to note that the cyclopentadienyl-cobalt-1,3

Computational study of productive and non-productive cycles in fluoroalkene metathesis

• Markéta Rybáčková,
• Jan Hošek,
• Ondřej Šimůnek,
• Viola Kolaříková and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2015, 11, 2150–2157, doi:10.3762/bjoc.11.232

• alkenes to hydrofluoroalkenes. Moreover, just recently a successful cross metathesis of perfluoroalkenes with vinyl ethers has been published [35]. The reported computations dealing with the metathesis of fluoroalkenes are also extremely scarce. Thus, the mechanism of the cross metathesis of norbornene

• , where the relative stability of the latter was by 100 kJ/mol higher compared to the anti coordination. These results are in agreement with the previous computations of a norbornene derivative with fluoroalkenes [36][37], but are suprisingly contradictory to the experimental observations of the reaction

Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• the use of 81 in the living ROMP of a hydrophilic norbornene monomer in air, leading to the formation of hydrogels [71]. Despite the living character of this reaction, the propagating catalyst was found to be inactive after 1 hour. Indenylidene complexes The indenylidene-bearing family of complexes

Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

• Shawna L. Balof,
• K. Owen Nix,
• Matthew S. Olliff,
• Sarah E. Roessler,
• Arpita Saha,
• Kevin B. Müller,
• Ulrich Behrens,
• Edward J. Valente and
• Hans-Jörg Schanz

Beilstein J. Org. Chem. 2015, 11, 1960–1972, doi:10.3762/bjoc.11.212

• norbornene (NBE) at 80 °C in microemulsion (91% conversion) [54]. The same conditions failed to polymerize significant amounts of the far less reactive monomers cyclooctene (COE) or cyclooctadiene (COD) with yields below 10%. Later, Heroguez et al. synthesized the 1st generation Grubbs-type macroinitiator 3

New aryloxybenzylidene ruthenium chelates – synthesis, reactivity and catalytic performance in ROMP

• Patrycja Żak,
• Szymon Rogalski,
• Mariusz Majchrzak,
• Maciej Kubicki and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2015, 11, 1910–1916, doi:10.3762/bjoc.11.206

• ) and a single selected norbornene derivative. Keywords: chemoactivation; latent catalysts; metathesis; ROMP; ruthenium; Introduction Olefin metathesis is nowadays one of the most important methods for the formation of carbon–carbon bonds in organic and polymer chemistry [1][2]. The availability of

• have also been independently studied by Skowerski and Grela [10]. Phenoxybenzylidene complexes have been demonstrated to behave like latent catalysts in common testing reactions involving ring opening metathesis polymerisation (ROMP) of COD, norbornene derivative and dicyclopentadiene as well as cross

• synthesized complexes were tested in ROMP of COD and a single selected norbornene derivative. Results and Discussion Synthesis Complexes containing triphenylphosphine ligands and substituted triphenylphosphine ligands were isolated in high yields (95–98%) according to the methodology described by Grubbs

Stereochemistry of ring-opening/cross metathesis reactions of exo- and endo-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitriles with allyl alcohol and allyl acetate

• Piotr Wałejko,
• Michał Dąbrowski,
• Lech Szczepaniak,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 1893–1901, doi:10.3762/bjoc.11.204

• resulted mixtures were easier to work-up and to separate from ROMP oligomers by simple filtration (see Figure 2). A different isomeric products distribution was observed in the mixtures of type A products (1-2 and 1-3). In reactions of exo- and endo-norbornene 1 and 2, with the acetate 3, approximately a

• references substances. RI values for phases type DB-5 and MS spectra for derivatives 5–12, realized at an ionization energy of 70 eV are shown in Supporting Information File 1. General ROCM procedure To a mixture of norbornene 1 or 2 and alkene (for details see Table 1 and Table 2) in anhydrous DCM a

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• systems Banti and co-workers have reported a tandem metathesis sequence with the aid of catalysts 1 and 2 starting with cyclohexene and norbornene systems containing allylamino moieties [19]. When the reaction was carried out in the presence of catalyst 2; RRM product 79 was observed in 29% yield along

• dimerized 16-membered ring product 101 in 57% yield, which was generated by a RRM–dimerization sequence and its monomer 100 in 14% yield along with 99 in 26% yield (Scheme 20). Bicyclo[2.2.1]heptene derivatives Holtsclaw and Koreeda [25] have explored a chemoselective RRM of the enone containing norbornene

• system such as 102. To this end, the spironorbornene 102 was subjected to a RRM sequence under the influence of catalyst 1 to deliver the RRM product 103 and the RCM product 104 in a 99:1 ratio. When norbornene derivative 102 was treated with catalyst 2 tricyclic compound 103 and spironorbornene

Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

• Yulia I. Denisova,
• Maria L. Gringolts,
• Alexander S. Peregudov,
• Liya B. Krentsel,
• Ekaterina A. Litmanovich,
• Arkadiy D. Litmanovich,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2015, 11, 1796–1808, doi:10.3762/bjoc.11.195

• achieve a random copolymer of norbornene and cyclooctene. Its rate is limited by the interaction of polyoctenamer-bound carbenes with polynorbornene units, which is hampered, presumably due to steric reasons. Polynorbornene-bound carbenes are detected in very low concentrations throughout the whole

• way to unsaturated multiblock statistical copolymers. Their structure can be controlled by the amount of catalyst, mixture composition, and reaction time. It is remarkable that this goal can be achieved with a catalyst that is not suitable for ring-opening metathesis copolymerization of norbornene and

• at the cross-metathesis stage [14]. In our previous communication [15] we reported the obtaining of a copolymer of norbornene (NB) and cis-cyclooctene (COE) by the cross-metathesis of polynorbornene (poly(1,3-cyclopentylenevinylene), PNB) with polyoctenamer (poly(1-octenylene), PCOE). It is

Grubbs–Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids

• Maximilian Koy,
• Hagen J. Altmann,
• Benjamin Autenrieth,
• Wolfgang Frey and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 1632–1638, doi:10.3762/bjoc.11.178

• unsubstituted norbornene (M1) and cis-cyclooctene (M6) but also with M4. However, in turn it allows for the synthesis of high molecular weight polymers. The most striking feature, however, is related to the Ru content of the resulting polymers, which were all obtained as white powders. Unlike in many other Ru

Synthesis of a tricyclic lactam via Beckmann rearrangement and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha,
• Ongolu Ravikumar and
• Jadab Majhi

Beilstein J. Org. Chem. 2015, 11, 1503–1508, doi:10.3762/bjoc.11.163

• demonstrated the RRM strategy with the norbornene derivative 2 to deliver the tricyclic compound 1 involving a short synthetic sequence. However, a similar compound 10a did not deliver the RRM product. For the first time, we have demonstrated that BR in combination with RRM is a useful strategy to generate

Thermal properties of ruthenium alkylidene-polymerized dicyclopentadiene

• Yuval Vidavsky,
• Yotam Navon,
• Yakov Ginzburg,
• Moshe Gottlieb and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2015, 11, 1469–1474, doi:10.3762/bjoc.11.159

• of suitable strained cycloolefins. DCPD is a common byproduct in the naphtha cracking process [19] and has two carbon–carbon double bonds, which readily undergo ROMP reactions with ruthenium alkylidenes. By adding the appropriate initiator, the highly strained and reactive norbornene double bond can

Design and synthesis of fused polycycles via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Ongolu Ravikumar

Beilstein J. Org. Chem. 2015, 11, 1259–1264, doi:10.3762/bjoc.11.140

• used to design new polycycles. In this regard, ruthenium alkylidene catalysts are effective in realizing the RRM of bis-norbornene derivatives prepared by DA reaction and Grignard addition. Here, fused polycycles are assembled which are difficult to produce by conventional synthetic routes. Keywords

• are well suited. Here, we demonstrate that an endocyclic bis-norbornene system undergoes an RRM with a suitably placed olefin moiety to generate complex polycyclic compounds. RRM of norbornene derivatives are common, however, reports dealing with RRM of bis-norbornene derivatives are rare [21][22

• ]. Herein, we report two unique examples where the synthesis of hexacyclic systems containing 10 stereocenters have been generated by the application of RRM of readily available bis-norbornene derivatives using Grubbs’ catalysts (Figure 1). The higher analogue related to the bicyclo[2.2.2] system is also

Intermolecular addition reactions of N-alkyl-N-chlorosulfonamides to unsaturated compounds

• Gerold Heuger and
• Richard Göttlich

Beilstein J. Org. Chem. 2015, 11, 1226–1234, doi:10.3762/bjoc.11.136

• , sterically not hindered alkene like 1-decene (Table 3, entry 1) still gave reasonable yields of the addition product. The yield is lower in addition to norbornene and cyclooctene, both of which are more sterically hindered and do not allow any mesomeric stabilization of the intermediate radical (Table 3

Superoxide chemistry revisited: synthesis of tetrachloro-substituted methylenenortricyclenes

• Basavaraj M. Budanur and
• Faiz Ahmed Khan

Beilstein J. Org. Chem. 2014, 10, 2531–2538, doi:10.3762/bjoc.10.264

• of the superoxide ion as a reagent in organic synthesis is still underexplored. A very few and scattered reports appeared in the literature for the conversion of bicyclic norbornene to substituted nortricyclenes (Scheme 1). In 1966 Kempter and co-workers [26] have synthesized nortricyclenes from

• nortricyclenes using palladium and zinc powder from norbornadiene. The bromination of norbornene [30][31][32] is another route to the nortricyclenes. Here, in this study we report an efficient method for the synthesis of aryl- and vinyl-substituted tetrachloromethylenenortricyclenes from the Diels–Alder (DA

Investigations of thiol-modified phenol derivatives for the use in thiol–ene photopolymerizations

• Sebastian Reinelt,
• Monir Tabatabai,
• Urs Karl Fischer,
• Norbert Moszner,
• Andreas Utterodt and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 1733–1740, doi:10.3762/bjoc.10.180

• ], adaptable thiol–ene networks [29], thiol–yne photopolymerizations [30][31][32], and thiol–norbornene materials [33] only to mention a few of them. However, the design of new monomers – both ene and thiol monomers – for thiol–ene polymerization is a sustained necessity in order to improve the mechanical