Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

• Andrzej Tracz,
• Mateusz Matczak,
• Katarzyna Urbaniak and
• Krzysztof Skowerski

Beilstein J. Org. Chem. 2015, 11, 1823–1832, doi:10.3762/bjoc.11.198

• Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM) and cross metathesis (CM) reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the

• vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities. Keywords: green solvents; macrocyclization; metathesis

• ; ruthenium; Introduction Olefin metathesis (OM) is a mild and versatile catalytic method which allows the formation of carbon–carbon double bonds [1]. Understanding the key events in ruthenium-catalyzed olefin metathesis [2] and developing efficient and selective catalysts [3] provides opportunities for

Preparation of conjugated dienoates with Bestmann ylide: Towards the synthesis of zampanolide and dactylolide using a facile linchpin approach

• Jingjing Wang,
• Samuel Z. Y. Ting and
• Joanne E. Harvey

Beilstein J. Org. Chem. 2015, 11, 1815–1822, doi:10.3762/bjoc.11.197

• . Although fragment syntheses vary, the late-stage fragment assembly of the dactylolide macrocycle has centred mostly around construction of the C1–C5 dienoate by Wittig-type olefination reactions followed by ester hydrolysis and esterification with the C19 hydroxy group, combined with metathesis to form the

• aldehyde fragment 6 by asymmetric alkynylation, and form the pyran using an oxa-Michael addition, in a manner reminiscent of that employed by Uenishi and co-workers [34]. Finally, macrocyclisation will be achieved through the well-established strategy of ring-closing metathesis at C8–C9. Results and

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

• Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova str. 28, 119991 Moscow, Russia Chemistry Department, Moscow State University, Leninskie gory 1, build. 3, 119991 Moscow, Russia 10.3762/bjoc.11.195 Abstract The cross-metathesis of polynorbornene and polyoctenamer in d

• 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

• cis-cyclooctene because of their substantially different monomer reactivities. Keywords: cross-metathesis; 1st generation Grubbs’ catalyst; interchange reactions; kinetics; multiblock copolymer; Introduction A desired sequence of monomer units in a polymer chain can be achieved not only in the

A comprehensive study of olefin metathesis catalyzed by Ru-based catalysts

• Albert Poater and
• Luigi Cavallo

Beilstein J. Org. Chem. 2015, 11, 1767–1780, doi:10.3762/bjoc.11.192

• species is also discussed, with either pyridine or phosphine ligands to dissociate. Keywords: cis; density functional theory (DFT); N-heterocyclic carbene; olefin metathesis; ruthenium; Introduction Organic synthesis is based on reactions that drive the formation of carbon–carbon bonds [1]. Olefin

• metathesis represents a metal-catalyzed redistribution of carbon–carbon double bonds [2][3][4][5][6] and provides a route to unsaturated molecules that are often challenging or impossible to prepare by any other means. Furthermore, the area of ruthenium-catalyzed olefin metathesis reactions is an outstanding

• halogen group to a trans position (side path in Scheme 2). Bearing the general acceptance [39][40][41][42][43][44][45] that olefin metathesis with Ru-catalysts starts from a bottom-bound olefin complex because of energetics, i.e., reporting higher energies for the possible side-bound olefin complexes

Design and synthesis of propellane derivatives and oxa-bowls via ring-rearrangement metathesis as a key step

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1727–1731, doi:10.3762/bjoc.11.188

• Sambasivarao Kotha Rama Gunta Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai-400 076, India 10.3762/bjoc.11.188 Abstract Various intricate propellane derivatives and oxa-bowls have been synthesized via a ring-rearrangement metathesis (RRM) as a key step starting

• from readily accessible starting materials such as p-benzoquinone, 1,4-naphthoquinone and 1,4-anthraquinone. Keywords: allylation; propellane derivatives; quinones; ring-rearrangement metathesis; Introduction The synthesis of complex target structures requires bond-disconnection analysis of the

• , the ring-rearrangement metathesis (RRM) [8][9][10][11][12] is useful and moreover, the stereochemical information can be transferred from the starting material to the final product during the RRM. In continuation of our interest to design novel molecules via metathesis [13][14][15][16][17][18][19][20

Progress in metathesis chemistry II

• Karol Grela

Beilstein J. Org. Chem. 2015, 11, 1639–1640, doi:10.3762/bjoc.11.179

• Karol Grela Biological and Chemical Research Centre, Faculty of Chemistry, University of Warsaw, Żwirki i Wigury 101, 02-089 Warsaw, Poland Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland 10.3762/bjoc.11.179 Keywords: olefin metathesis;   Joseph

• Conrad – The Shadow-Line Five years have passed since the first publication of the Thematic Series on Olefin Metathesis in the Beilstein Journal of Organic Chemistry [1]. During these years the research continued to progress at full speed. Astute readers of this Thematic Series, as well as readers of the

• recent books devoted to olefin metathesis [2][3], can easily see that a great number of studies in this field have advanced from the basic research phase to the commercial application stage. While new, active and more selective catalysts that solve some longstanding limitations are still being developed

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

• , Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany Institut für Textilchemie und Chemiefaser (ITCF) Denkendorf, Körschtalstr. 26, D-73770 Denkendorf, Germany 10.3762/bjoc.11.178 Abstract The novel dicationic metathesis catalyst [(RuCl2(H2ITapMe2)(=CH–2-(2-PrO)-C6H4))2+ (OTf−)2] (Ru-2

• , H2ITapMe2 = 1,3-bis(2’,6’-dimethyl-4’-trimethylammoniumphenyl)-4,5-dihydroimidazol-2-ylidene, OTf− = CF3SO3−) based on a dicationic N-heterocyclic carbene (NHC) ligand was prepared. The reactivity was tested in ring opening metathesis polymerization (ROMP) under biphasic conditions using a nonpolar organic

• solvent (toluene) and the ionic liquid (IL) 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [BDMIM+][BF4−]. The structure of Ru-2 was confirmed by single crystal X-ray analysis. Keywords: biphasic catalysis; ionic initiators; recycling; ROMP; ruthenium; Introduction Ionic metathesis catalysts offer

Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

• Thibault E. Schmid,
• Florian Modicom,
• Adrien Dumas,
• Etienne Borré,
• Loic Toupet,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 1541–1546, doi:10.3762/bjoc.11.169

• -diisopropylphenyl)imidazolidin-2-ylidene) demonstrated excellent latent behaviour in ring closing metathesis (RCM) reaction and could be activated in the presence of a Brønsted acid. The versatility of the catalyst 4a was subsequently demonstrated in RCM, cross-metathesis (CM) and enyne metathesis reactions

• . Keywords: latent catalyst; olefin metathesis; picolinate ligand; ruthenium indenylidene; Introduction Olefin metathesis has witnessed tremendous development in the last decades and has emerged as a powerful tool with dramatic impact on both organic chemistry and materials science [1][2]. Intensive

• in model ring closing metathesis and cross-metathesis transformations. Results and Discussion With the objective to develop an attractive strategy for the synthesis of indenylidene-picolinic ruthenium complexes, we initially attempted their preparation using a silver-free methodology. In fact, silver

Ruthenium indenylidene “1^st generation” olefin metathesis catalysts containing triisopropyl phosphite

• Stefano Guidone,
• Fady Nahra,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2015, 11, 1520–1527, doi:10.3762/bjoc.11.166

• ” cis-complexes. These have been used in olefin metathesis reactions. The cis-Ru species exhibit noticeable differences with the trans-Ru parent complexes in terms of structure, thermal stability and reactivity. Experimental data underline the importance of synergistic effects between phosphites and L

• -type ligands. Keywords: 1st generation; indenylidene; metathesis; phosphite; ruthenium; Introduction The olefin metathesis reaction is a powerful tool for C–C bond formation in the synthesis of highly valuable organic compounds [1][2][3][4]. Protocols involving W-, Mo- and Ru-based pre-catalysts can

• ’-bis[2,4,6-(trimethyl)phenyl]imidazolidin-2-ylidene) afforded a Ru pre-catalyst displaying an unusual cis-geometry [25]. cis-Caz-1, which is more thermodynamically stable than its trans-isomer represents a breakthrough in catalyst-design for metathesis reactions of challenging hindered substrates

Design and synthesis of hybrid cyclophanes containing thiophene and indole units via Grignard reaction, Fischer indolization and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Ajay Kumar Chinnam and
• Mukesh E. Shirbhate

Beilstein J. Org. Chem. 2015, 11, 1514–1519, doi:10.3762/bjoc.11.165

• via Grignard addition, Fischer indolization and ring-closing metathesis as key steps. Keywords: cyclophane; Grignard reaction; Fischer indolization; ring-closing metathesis; Introduction Modern olefin metathesis catalysts enable a late stage ring-closing step starting with bisolefinic substrates

• containing polar functional groups [1]. As part of a major program aimed at developing new and intricate strategies to cyclophanes [2][3][4][5][6][7][8][9][10], we envisioned various building blocks [11] by ring-closing metathesis (RCM) as a key step [12][13][14][15][16][17][18][19][20][21][22][23][24][25

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

• -rearrangement metathesis as key steps. Here, we used a simple starting material such as dicyclopentadiene. Keywords: allylation; Beckmann rearrangement; lactams; oximes; ring-rearrangement metathesis; Introduction The Beckmann rearrangement (BR), a well-known protocol for the conversion of ketoxime to an

• reaction at the oxime nitrogen is useful [1][2][3][4][5][6]. Here, we plan to use the BR in combination with a ring-rearrangement metathesis (RRM) [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] to generate lactam derivative 1. The RRM protocol involves a tandem process with several

• metathetic transformations such as ring-closing metathesis (RCM) and ring-opening metathesis (ROM). The RRM has emerged as a powerful tool in organic synthesis because of its ability to transform simple starting materials into complex targets involving an ingenious design. The retrosynthetic strategy to the

Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds

• Javier Miró,
• María Sánchez-Roselló,
• Álvaro Sanz,
• Fernando Rabasa,
• Carlos del Pozo and
• Santos Fustero

Beilstein J. Org. Chem. 2015, 11, 1486–1493, doi:10.3762/bjoc.11.161

• Abstract A new tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of

• linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM–IMDAR protocols. Keywords: bicyclic frameworks; cross enyne metathesis; Diels–Alder

• reaction; tandem reaction; Introduction Among all metathetic processes, the enyne metathesis reaction has received significant attention as an attractive and frequently used synthetic tool in organic synthesis [1][2][3][4][5][6][7]. It is an atom economical process that combines alkene and alkyne moieties

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

• : glass-transition temperature; polydicyclopentadiene; ring opening metathesis polymerization; ruthenium-catalyzed olefin metathesis; thermoset polymers; Introduction Olefin metathesis [1][2][3][4][5][6] has advanced to become a major synthetic tool in academia [7][8][9][10][11] and industry [12

• ]. Metathesis polymerization techniques [13][14][15], and especially ring opening metathesis polymerization (ROMP) [16][17], have had a vital role in this growth. Polydicyclopentadiene (PDCPD), probably the most widely used metathesis polymer, is formed through ROMP of mostly endo-dicyclopentadiene (DCPD, 1

• ) (Figure 1). The Grubbs-type ruthenium initiators, known for their high activity, stability and functional group tolerance are extensively used to promote this type of olefin metathesis reactions. For example, the Grubbs second generation catalyst 2 [18] (Figure 1), may be used to initiate ROMP reactions

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• Arabia 10.3762/bjoc.11.158 Abstract Two ruthenium olefin metathesis initiators featuring electronically modified quinoline-based chelating carbene ligands are introduced. Their reactivity in RCM and ROMP reactions was tested and the results were compared to those obtained with the parent unsubstituted

• reactivity of the complexes. Keywords: DFT calculations; olefin metathesis; ring closing metathesis; ring-opening metathesis polymerisation; ruthenium; Introduction Olefin metathesis is a catalytic process during which C–C double bonds are exchanged [1]. Since the first examples were published in the 1950s

• basic structure of ruthenium-based olefin metathesis catalysts led to a diversification of catalytic profiles (Figure 1) [5][6]. Perhaps the most important one was the introduction of bidentate benzylidene ligands instead of simple alkylidenes, thus giving rise to the class of Hoveyda-type complexes

Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes

• Ivan Šnajdr,
• Kamil Parkan,
• Filip Hessler and
• Martin Kotora

Beilstein J. Org. Chem. 2015, 11, 1392–1397, doi:10.3762/bjoc.11.150

• Praha 6, Czech Republic 10.3762/bjoc.11.150 Abstract Cross-metathesis of α- and β-vinyl C-deoxyribosides and α-vinyl C-galactoside with various terminal alkenes under different conditions was studied. The cross-metathesis of the former proceeded with good yields of the corresponding products in

• ; catalysis; carbohydrates; cross-metathesis; ruthenium; Introduction Natural and unnatural C-substituted glycosides are important compounds with a plethora of attractive biological properties and they often have been used as artificial DNA components [1]. Among various synthetic procedures providing C

• corresponding vinyl α-C-deoxyriboside α-2 and β-C-deoxyriboside β-2 [16]. As far as further transformation of vinyl C-deoxyribosides relying on the metathesis reaction is concerned, only one paper dealing with successful cross-metathesis with 4-vinyl-5-methyl-2-oxazolone has been reported [16]. This finding is

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

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1373–1378, doi:10.3762/bjoc.11.148

• -rearrangement metathesis (RRM) as the key steps. This approach delivers tri- and tetracyclic sulfones with six (n = 1), seven (n = 2) or eight-membered (n = 3) fused-ring systems containing trans-ring junctions unlike the conventional all cis-ring junctions generally obtained during the RRM sequence

• . Interestingly the starting materials used are simple and commercially available. Keywords: alkenylation; Diels–Alder reaction; ring-rearrangement metathesis; sulfones; Introduction Sulfones [1][2][3][4][5][6][7][8] are popular building blocks [9] in organic synthesis. They are also useful substrates for the

• Ramberg–Bäcklund reaction [10] and they can be alkylated via carbanion chemistry. Moreover, they are suitable synthons in Diels–Alder (DA) reactions [11][12][13][14]. In view of various applications of sulfone derivatives, we envisioned a new synthetic strategy based on ring-rearrangement metathesis (RRM

Spiro annulation of cage polycycles via Grignard reaction and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Mohammad Saifuddin,
• Rashid Ali and
• Gaddamedi Sreevani

Beilstein J. Org. Chem. 2015, 11, 1367–1372, doi:10.3762/bjoc.11.147

• -pyrano cage compound 7 involving ring-closing metathesis is reported. The hexacyclic dione 10 was prepared from simple and readily available starting materials such as 1,4-naphthoquinone and cyclopentadiene. The synthesis of an unprecedented octacyclic cage compound through intramolecular Diels–Alder (DA

• ) reaction as a key step is described. The structures of three new cage compounds 7, 12 and 18 were confirmed by single crystal X-ray diffraction studies. Keywords: cage molecules; Diels–Alder reaction; Grignard reaction; ring-closing metathesis; spirocycles; Introduction Design and synthesis of

• -closing metathesis (RCM) are considered as viable options. The retrosynthetic analysis to the target bis-spiro-cage compound 7 is shown in Figure 2. The target compound 7 could be obtained from O-allylation of the Grignard addition product 11 followed by the two-fold RCM sequence. The required cage dione

Pd(OAc)₂-catalyzed dehydrogenative C–H activation: An expedient synthesis of uracil-annulated β-carbolinones

• Biplab Mondal,
• Somjit Hazra,
• Tarun K. Panda and
• Brindaban Roy

Beilstein J. Org. Chem. 2015, 11, 1360–1366, doi:10.3762/bjoc.11.146

• mechanistic pathway that commence with electrophilic metalation at the indole C3 postion. The nucleophilicity of indole at C3 is well known [58] and a similar kind of electrophilic reaction leads to the intermediate A (Scheme 3). We believe this intermediate then undergoes a σ-bond metathesis reaction to form

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

• cyclophanes. To keep the length of the review at a manageable level the literature related to orthocyclophanes was not included. Keywords: addition reactions; coupling reactions; cyclophane; metathesis; muscopyridine; name reactions; natural products; Indroduction Cyclophanes [1][2][3][4][5][6][7][8][9][10

• -binding abilities, an improved affinity can be achieved by polytopic hosts [61][62][63] through multivalency effects in macrocycles. Olefin metathesis has played a key role in the development of cyclophane chemistry. Some of the catalysts used for this purpose are listed in Figure 3. The development of

• agents in the presence of Cu(II). Fürstner and co-workers [72] have reported the total synthesis of natural products 22–24 by using a metathesis reaction [73][74][75][76][77][78][79][80][81][82] as the key step. The ring-closing metathesis (RCM) has been utilized for the synthesis of the turriane with a

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

• Sambasivarao Kotha Ongolu Ravikumar Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai-400 076, India, Fax: 022-25767152 10.3762/bjoc.11.140 Abstract Atom efficient processes such as the Diels–Alder reaction (DA) and the ring-rearrangement metathesis (RRM) have been

• : Diels–Alder reaction; Grignard addition; ring-rearrangement metathesis; polycycles; Introduction Design and synthesis of complex polycycles in a minimum number of steps will enhance the overall synthetic economy of the preparation of a target molecule. The ring-rearrangement metathesis (RRM) is a

• ; HRMS (Q–ToF) m/z: [M + Na]+ calcd for C25H32NaO2, 387.2295; found, 387.2292. Commercially available ruthenium catalysts used in RRM metathesis. Crystal structure of 5 with thermal ellipsoids drawn at 50% probability level. Synthesis of hexacyclic compound 6a by using an RRM approach. Synthesis of

New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

• Rym Hassani,
• Mahjoub Jabli,
• Yakdhane Kacem,
• Jérôme Marrot,
• Damien Prim and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132

• )-di-μ-acetatobis[1-(4-isopropyloxazolin-2-yl)naphthalen-2-yl-C,N]dipalladium(II) (3) (Scheme 1). Unfortunately, complex dimer 3 was relatively unstable, so only its 1H NMR and FTIR data were performed. The metathesis of dimer 3 with lithium chloride in acetone afforded the more stable (S,S)-dimer 4 in

• cool to rt and filtered through celite. The solvent was evaporated, and the crude product was recrystallized from ether/petroleum ether to obtain 3 (89%). The metathesis of dimer 3 (0.196 mmol, 1 equiv) with LiCl (18.5 mg, 0.43 mmol, 2.2 equiv) in acetone (7.0 mL) at room temperature for 24 h afforded

Hybrid macrocycle formation and spiro annulation on cis-syn-cis-tricyclo[6.3.0.0^2,6]undeca-3,11-dione and its congeners via ring-closing metathesis

• Sambasivarao Kotha,
• Ajay Kumar Chinnam and
• Rashid Ali

Beilstein J. Org. Chem. 2015, 11, 1123–1128, doi:10.3762/bjoc.11.126

• based macrocycle 6 involving Fischer indolization and ring-closing metathesis (RCM). Various spiro-polyquinane derivatives have been assembled via RCM as a key step. Keywords: aza-polyquiananes; Fischer indolization; macrocycles; ring-closing metathesis; spiropolyquinanes; Introduction Design and

• new strategy based on Fischer indolization and ring-closing metathesis as the key steps. To develop a simple synthetic methodology to aza-polycycles and spiropolycycles from readily available starting materials [47][48][49][50][51][52], bicyclic, tricyclic and pentacyclic diones (1–3) were identified

• ]. Also, based on Fischer indolization and ring-closing metathesis (RCM), we have developed a new strategy to indole-based propellane derivatives [57]. Here, the tricyclic dione 2 required was prepared starting with the Cookson’s dione 4 in two steps involving flash vacuum pyrolysis (FVP) and

Further exploration of the heterocyclic diversity accessible from the allylation chemistry of indigo

• Alireza Shakoori,
• John B. Bremner,
• Mohammed K. Abdel-Hamid,
• Anthony C. Willis,
• Rachada Haritakun and
• Paul A. Keller

Beilstein J. Org. Chem. 2015, 11, 481–492, doi:10.3762/bjoc.11.54

• -closing metathesis of the N,O-diallylic spiro structure and subsequent Claisen rearrangement gave rise to the new (1R,8aS,17aS)-rel-1,2-dihydro-1-vinyl-8H,17H,9H-benz[2',3']pyrrolizino[1',7a':2,3]pyrido[1,2-a]indole-8,17-(2H,9H)-dione heterocyclic system. Keywords: allylation; cascade reactions; indigo

• structural complexity through post-allylation ring-closing metathesis, plus new biological activity investigations, which are now reported herein. Results and Discussion A range of strategies are available to potentially control reaction-path selectivity in cascade pathways [5][6] but in these indigo

• 12, with its pendant allyl substituents, affords an ideal substrate for a ring-closing metathesis reaction. In the event, treatment of 12 with Grubbs' II catalyst at reflux in CH2Cl2 produced not the expected 9-membered ring, but rather the novel fused heterocycle 31 in 70% isolated yield (Scheme 10

Synthesis and chemosensing properties of cinnoline-containing poly(arylene ethynylene)s

• Natalia A. Danilkina,
• Petr S. Vlasov,
• Semen M. Vodianik,
• Andrey A. Kruchinin,
• Yuri G. Vlasov and
• Irina A. Balova

Beilstein J. Org. Chem. 2015, 11, 373–384, doi:10.3762/bjoc.11.43

• with 1,4-diiodo-2,5-bis(octyloxy)benzene (9). There are two main reactions of polycondensation that have been reported as synthetic approaches towards PAEs: the acyclic diyne metathesis polymerization (ADIMET) [55] and the Sonogashira coupling [56]. Both of them have their own advantages and drawbacks

Copper-catalyzed cascade reactions of α,β-unsaturated esters with keto esters

• Zhengning Li,
• Chongnian Wang and
• Zengchang Li

Beilstein J. Org. Chem. 2015, 11, 213–218, doi:10.3762/bjoc.11.23

• -lactone with a γ-exo-ester group, in 90% yield (Table 1, entry 1). Since the existing methyl methacrylate may also compete as the enolate acceptor, the high yield of 3aa indicate that lactonization of the aldolization alkoxide B proceeded much faster than metathesis of B with a silane, which gave γ