Continuous flow nitration in miniaturized devices

• Amol A. Kulkarni

Beilstein J. Org. Chem. 2014, 10, 405–424, doi:10.3762/bjoc.10.38

• Knapkiewicz et al. [37] (Scheme 11). The product 2-isopropoxy-5-nitrobenzaldehyde (37) is an intermediate to obtain a nitro-substituted Hoveyda–Grubbs catalyst. Scale-up based on the conventional batch approach yielded a higher extent of the undesired regioisomer 38 (37% rise than the laboratory scale batch

Novel supramolecular affinity materials based on (−)-isosteviol as molecular templates

• Christina Lohoelter,
• Malte Brutschy,
• Daniel Lubczyk and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2013, 9, 2821–2833, doi:10.3762/bjoc.9.317

• ), employing the 2nd generation Grubbs catalyst in refluxing dichloromethane. Even after prolonged reaction times, complete conversion of the starting material could not be achieved. However, the formation of a sole product was observed. Upon chromatographic separation, the product was obtained, exhibiting a

Synthesis of indole-based propellane derivatives via Weiss–Cook condensation, Fischer indole cyclization, and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Ajay Kumar Chinnam and
• Arti Tiwari

Beilstein J. Org. Chem. 2013, 9, 2709–2714, doi:10.3762/bjoc.9.307

• treated with 5-bromo-1-pentene in the presence of NaH to generate the unsymmetrical diketone 8. Having compound 3 in hand, our next task was to construct the propellane derivatives via RCM by using Grubbs catalyst. In this regard, compound 3 was subjected to RCM under the influence of Grubbs 2nd

One-pot cross-enyne metathesis (CEYM)–Diels–Alder reaction of gem-difluoropropargylic alkynes

• Santos Fustero,
• Paula Bello,
• Javier Miró,
• María Sánchez-Roselló,
• Günter Haufe and
• Carlos del Pozo

Beilstein J. Org. Chem. 2013, 9, 2688–2695, doi:10.3762/bjoc.9.305

• generation Hoveyda–Grubbs catalyst generates a diene moiety which in situ reacts with a wide variety of dienophiles giving rise to a small family of new fluorinated carbo- and heterocyclic derivatives in moderate to good yields. This is a complementary protocol to the one previously described by our research

• generation Hoveyda–Grubbs catalyst I was heated under ethylene atmosphere (1 atm) for 2 h, the clean formation of diene 2a was observed. This newly formed diene was isolated in 70% yield and it reacted smoothly with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione as dienophile at room temperature to afford, after

Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C₂-symmetric building block: a strategy for the synthesis of decanolide natural products

• Bernd Schmidt and
• Oliver Kunz

Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289

• , entry 4). With these catalyst loadings self metathesis of 8 is largely suppressed and the chromatographic isolation of 11 is facilitated, which might explain the improved yields under these conditions. With second generation Grubbs’ catalyst B, the self metathesis of the supposedly less reactive CM

Algicidal lactones from the marine Roseobacter clade bacterium Ruegeria pomeroyi

• Ramona Riclea,
• Julia Gleitzmann,
• Hilke Bruns,
• Corina Junker,
• Barbara Schulz and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2012, 8, 941–950, doi:10.3762/bjoc.8.106

• , syntheses of reference compounds were carried out (Scheme 1). Methacryloyl chloride (12) was esterified with but-3-en-2-ol (13) in the presence of triethylamine to yield but-3-en-2-yl methacrylate (15). Ring-closing metathesis with Grubbs catalyst of the second generation gave 2-methylpent-2-en-4-olide (11

• ), 990 (w), 930 (m), 810 (w), 657 (w) cm−1; UV–vis: λmax (log ε): 228 (2.83) nm. General procedure for the ring-closing metathesis to butenolides: Grubbs catalyst of the second generation (0.05 equiv) was added to a solution of the ester 15 or 16 (1.0 equiv) in dry dichloromethane (0.05 M). The mixture

Binding of group 15 and group 16 oxides by a concave host containing an isophthalamide unit

• Jens Eckelmann,
• Vittorio Saggiomo,
• Svenja Fischmann and
• Ulrich Lüning

Beilstein J. Org. Chem. 2012, 8, 11–17, doi:10.3762/bjoc.8.2

• (1,3)-tribenzenabicyclo[10.10.5]heptacosaphan-6,17-dien-24,26-dione Anhydrous dichloromethane (800 mL) was added to a mixture of N,N'-bis-(2,6-bis[pent-4-enyloxy]-phenyl)-5-tert-butyl-isophthalamide (5, 1.00 g, 1.41 mmol) and Grubbs Catalyst 1st gen. (162 mg, 141 µmol). The solution was stirred for 24

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• ) and ester group reduction (LiBH4), a protected racemic diene 16 was obtained; RCM cyclization of the latter using the Grubbs catalyst Cl2(PCy3)2Ru=CH–CH=CPh2 (3) led to the racemic dehydroprolinol derivative 17 in high yield. Subsequent O-protection with trityl chloride and dihydroxylation (with OsO4

• resolution in the ester reduction step, enantiopure (+)-21 was obtained. 1st-generation Grubbs catalyst was used for the RCM of (+)-21. It should be noted that the yield of (+)-22 in RCM (10 mol % 2, in benzene) was temperature dependent (88% at room temperature and 98% at 80 °C). Further stereocontrolled

• diastereomer. The nitrogen atom in 25 was then Boc-protected, debenzylated, and allylated to give the diene 26. RCM of the latter with 1st-generation Grubbs catalyst (10 mol % 2, in dichloromethane, at room temperature) provided the pyrrole scaffold 27. Subsequent stereoselective dihydroxylation (OsO4 and 4

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• ethylene at room temperature [39][41][42]. When the substrates were not reactive under these mild conditions, cross-metathesis efficiency was improved by using higher ethylene pressure [43] or changing the ruthenium precursor to the second generation Grubbs catalyst II and adjusting temperature and

• introduced in 1997 with the first generation Grubbs catalyst II [40] and the initial results indicated that propargylic alcohol derivatives and terminal olefins with oxygen-containing functional groups were well tolerated [57]. As emphasized in the introduction, self-metathesis of the terminal olefin in the

• by Blechert that EYCM reactions could be performed starting from either the olefin or the alkyne substrate bound to a support [58][59][60]. An improvement of the EYCM was achieved with the second generation Grubbs catalyst II starting from terminal alkynes, especially sterically hindered ones. More

Olefin metathesis in nano-sized systems

• Didier Astruc,
• Abdou K. Diallo,
• Sylvain Gatard,
• Liyuan Liang,
• Cátia Ornelas,
• Victor Martinez,
• Denise Méry and
• Jaime Ruiz

Beilstein J. Org. Chem. 2011, 7, 94–103, doi:10.3762/bjoc.7.13

• ]. The latter was perallylated to yield a deca-allylated cobalticinium, and then RCM of the organometallic complex proceeded to afford a pentacyclopentylcyclopentadienyl Co sandwich complex using the first-generation Grubbs catalyst [Ru(PCy3)2Cl2(=CHPh)], 3. Activation of mesitylene by the CpFe+ moiety

• an intermediate tetracyclic iron arene complex. Furthermore and interestingly, when the metathesis reaction was carried out in refluxing dichloroethane with the addition of the second-generation Grubbs catalyst [RuCl2(=CHPh)(bis-N-mesityl-NHC)], 7, (Scheme 3, NHC = N-heterocyclic carbene), the di

• catalysis in water and with down to 0.04 % of the second-generation Grubbs catalyst 7 for RCM, (Table 1) [63]. The dendrimer 11 contains triethylene glycol termini that solubilize it in water. In this way, the dendrimer serves as a molecular micelle [64][65] to solubilize the hydrophobic catalysts and

Hoveyda–Grubbs type metathesis catalyst immobilized on mesoporous molecular sieves MCM-41 and SBA-15

• Hynek Balcar,
• Tushar Shinde,
• Naděžda Žilková and
• Zdeněk Bastl

Beilstein J. Org. Chem. 2011, 7, 22–28, doi:10.3762/bjoc.7.4

• catalysts was reported [20]. A second generation Hoveyda–Grubbs catalyst was immobilized on silica without any linkers by simply placing the Ru complex in contact with silica in a suspension. Heterogeneous catalysts (loading from 0.05 to 0.6 wt % Ru) were prepared, which were active in ring-opening

• ) were obtained in high yields (70% and 64% for 3/MCM-41 and 3/SBA-15, respectively) after 3 h. The catalysts 3/MCM-41 and 3/SBA-15 exhibited some features similar to those of Hoveyda–Grubbs catalyst immobilized on silica [20]: (a) Filtration experiments proved complete catalyst heterogeneity only for

• led to high molecular weight polymers, whereas in [20] the formation of polymer was not referred. Interaction between the Ru complex and the support For Hoveyda–Grubbs catalyst immobilized on silica, the authors in [20] proposed a direct chemical interaction between the Ru species and the silanol

The catalytic performance of Ru–NHC alkylidene complexes: PCy₃ versus pyridine as the dissociating ligand

• Stefan Krehl,
• Diana Geißler,
• Sylvia Hauke,
• Oliver Kunz,
• Lucia Staude and
• Bernd Schmidt

Beilstein J. Org. Chem. 2010, 6, 1188–1198, doi:10.3762/bjoc.6.136

• on a theme by Grubbs”, as so accurately phrased by Fürstner [7], have been published. In the early stages of catalyst evolution improved methods for the introduction of the alkylidene ligand were the main focus. Thus, the original version of first generation Grubbs’ catalyst (A) [8], in which the

• particular complex D, which became known as second generation Grubbs’ catalyst [16], and the Umicore M2 catalyst E [17][18]. The ligation of strongly σ-donating NHC’s leads to an improvement of catalytic activity, which sometimes equals the activity of Mo-based catalysts while maintaining the general

• dihydropyran 2 was observed, compared to 89% conversion with the analogous indenylidene complex E. This result seems to contradict the observations by Adjiman, Taylor et al. who reported preparatively useful conversions and yields for second generation Grubbs’ catalyst D in acetic acid [49], however, their

Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

• Yannick Borguet,
• Xavier Sauvage,
• Guillermo Zaragoza,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2010, 6, 1167–1173, doi:10.3762/bjoc.6.133

• the Ru(II)–Ru(III) mixed-valence compound [(p-cymene)Ru(μ-Cl)3RuCl2(PCy3)], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions. Keywords: Grubbs catalyst; indenylidene ligands; Kharasch reaction; microwave heating; olefin

About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

• Hatice Mutlu,
• Lucas Montero de Espinosa,
• Oĝuz Türünç and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131

• -imidazolidinylidene)dichloro(2-(1-methylacetoxy)phenyl]methylene ruthenium(II) (Umicore, C3), (1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene)dichloro(o-isopropoxyphenylmethylene) ruthenium(II) (Hoveyda–Grubbs catalyst 2nd generation, C4, Sigma–Aldrich). General Methods Thin layer chromatography (TLC) was

Miniemulsion polymerization as a versatile tool for the synthesis of functionalized polymers

• Daniel Crespy and
• Katharina Landfester

Beilstein J. Org. Chem. 2010, 6, 1132–1148, doi:10.3762/bjoc.6.130

• of Grubbs catalyst in water. Although the first approach could yield simultaneously high conversion and stable latexes, particles with sizes above 400 nm without coagulum and 100% conversion could be obtained with the second approach. A water-soluble ruthenium carbene complex (PEO-based catalyst) was

Synthesis and crossover reaction of TEMPO containing block copolymer via ROMP

• Olubummo Adekunle,
• Susanne Tanner and
• Wolfgang H. Binder

Beilstein J. Org. Chem. 2010, 6, No. 59, doi:10.3762/bjoc.6.59

• catalysts for ROMP were based on molybdenum alkylidene catalysts, however, the true breakthrough of the method was hampered by the restricted functional group tolerance of Schrock initiators due to their sensitivity towards protic solvents and air [6]. With the advent of the Grubbs’ catalyst G1 (see Scheme

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

Facile synthesis of two diastereomeric indolizidines corresponding to the postulated structure of alkaloid 5,9E- 259B from a Bufonid toad (Melanophryniscus)

• Angela Nelson,
• H. Martin Garraffo,
• Thomas F. Spande,
• John W. Daly and
• Paul J. Stevenson

Beilstein J. Org. Chem. 2008, 4, No. 6, doi:10.1186/1860-5397-4-6

• 5,9E-259B, and b) synthetic 7. Structure shown with relative configuration. Reagents: (i) MeMgI. 96% (ii) PTSA 71%. (iii) TiCl4 CH2Cl2 25 oC 3d 68%. (iv) MsCl, Et3N, THF -40 oC, 74%. (v) Grubbs' catalyst, 25 oC CH2Cl2, 90%. (vi) H2 MeOH Pt/C 79%. (vii) LiAlH4, AlCl3, 73%. (viii) (a) Dess Martin

Desymmetrization of 7-azabicycloalkenes by tandem olefin metathesis for the preparation of natural product scaffolds

• Wolfgang Maison,
• Marina Büchert and
• Nina Deppermann

Beilstein J. Org. Chem. 2007, 3, No. 48, doi:10.1186/1860-5397-3-48

• 13 and 16 were generated after deprotection under standard acylation conditions in good yields. Treatment of these bis-olefins with Grubbs catalyst 1 gave the expected bicyclic compounds 14 and 17 in good yield along with some byproducts 15 and 18, respectively. These byproducts are often observed

Synthesis of densely functionalized enantiopure indolizidines by ring- closing metathesis (RCM) of hydroxylamines from carbohydrate- derived nitrones

• Marco Bonanni,
• Marco Marradi,
• Francesca Cardona,
• Stefano Cicchi and
• Andrea Goti

Beilstein J. Org. Chem. 2007, 3, No. 44, doi:10.1186/1860-5397-3-44

• was observed under these conditions. Ring-closing metathesis (RCM) of O-acetylhydroxylamines 8–10 using the second generation Grubbs' catalyst 11 [30] in refluxing CH2Cl2 afforded compounds 12–14 in nearly quantitative yields (Scheme 3). However, compounds 12 and 13 suffered from low stability and for

• α,α'-disubstituted hydroxylamines 3. Synthesis of piperidines 15–16 and azepine 17. Reagents and conditions: a) Ac2O, THF, 1 h, rt for 8 and 9, reflux for 10; b) 2nd generation Grubbs' catalyst 11 (5 mol%), CH2Cl2, reflux, 5.5 h; c) KHCO3, MeOH, rt, 12 h; d) Zn, AcOH, rt, 2 h. Synthesis of

Reaction of benzoxasilocines with aromatic aldehydes: Synthesis of homopterocarpans

• Míriam Álvarez-Corral,
• Cristóbal López-Sánchez,
• Leticia Jiménez-González,
• Antonio Rosales,
• Manuel Muñoz-Dorado and
• Ignacio Rodríguez-García

Beilstein J. Org. Chem. 2007, 3, No. 5, doi:10.1186/1860-5397-3-5

• of 2-allylphenol (3) (or conveniently functionalized derivatives) with allylchlorodimethylsilane followed by RCM with 2nd generation Grubbs catalyst [20] leads to the cyclic siloxane with high yields (Scheme 2). The good results in the cyclization step make this approach an excellent way of

• . Reagents: i CH2 = CHCH2SiMe2Cl, Et3N, DCM, 85%; ii 2nd generation Grubbs catalyst, DCM, 91%. Reagents: i: BF3·Et2O (1 eq), MeOH 95%; ii: substituted benzaldehydes, BF3·Et2O (1 eq), DCM; iii: substituted benzaldehydes, BF3·Et2O (2 eq), DCM; see Table 1 for cis/trans ratios and yields. Reagents: i: a) OsO4