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

• -diallylmalonate [1]. Contrastingly, this catalyst precursor was almost inactive in the self-metathesis of styrene, as stilbene formation leveled off after a few minutes without going past the 10% threshold. We attributed this negative result to a rapid degradation of the active species via a bimolecular pathway

Pd-catalyzed decarboxylative Heck vinylation of 2-nitrobenzoates in the presence of CuF₂

• Lukas J. Gooßen,
• Bettina Zimmermann and
• Thomas Knauber

Beilstein J. Org. Chem. 2010, 6, No. 43, doi:10.3762/bjoc.6.43

• yield 2-nitro-stilbene (3aa) as a model reaction, and investigated the catalytic activity of various combinations of palladium precursors, additives and oxidants (Table 1). The choice of an electron-deficient benzoic acid was motivated by our intention to overcome substrate limitations observed in Myers

Control of stilbene conformation and fluorescence in self-assembled capsules

• Mark R. Ams,
• Dariush Ajami,
• Stephen L. Craig,
• Jye-Shane Yang and
• Julius Rebek Jr

Beilstein J. Org. Chem. 2009, 5, No. 79, doi:10.3762/bjoc.5.79

• , Duke University, Durham, NC, 27708-0346, U.S. Department of Chemistry, National Taiwan University, No. 1. Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan 10.3762/bjoc.5.79 Abstract The extensively studied trans-stilbene molecule is known to give only weak fluorescence in solution and inside loosely

• -fitting synthetic capsules. However, trans-stilbene has been recently studied in the context of antibody interiors, where binding results in strong blue fluorescence. The present research was undertaken to understand the spatial factors that influence stilbene fluorescence. trans-Stilbene was encapsulated

• in the snug, self-assembled complex 1.1 and exhibited fluorescence quenching due to the distortion of its ground-state geometry. When the complex is elongated by incorporating glycouril spacers, trans-stilbene is allowed to adapt a fully coplanar arrangement and fluorescence returns. Keywords

Solvent-free phase-vanishing reactions with PTFE (Teflon^®) as a phase screen

• Kevin Pels and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2009, 5, No. 75, doi:10.3762/bjoc.5.75

• purity. Keywords: bromination; phase-vanishing; PTFE; solvent-free; stilbene; Findings Phase-vanishing (PV) reactions are triphasic reactions, which involve a reagent, a liquid perfluoroalkane and a substrate [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In a test tube, a liquid

• reacted to give a non-volatile product. We chose bromination reactions as a model system for the initial studies of solvent-free PV-PTFE reaction as bromine vapors are visible and the progress of a reaction could be easily monitored (Table 1). In the cource of bromination of cis-stilbene, shown in Figure

• with aqueous thiosulfate) (Figure 2d). Organic reactions on powdered solid substrates are known [22] and bromination of solid trans-stilbene under solvent-free PV-PTFE conditions worked well (Table 1, entry 6). Due to its lower reactivity, bromine vapors were present in the flask throughout the

Ring strain and total syntheses of modified macrocycles of the isoplagiochin type

• Andreas Speicher,
• Timo Backes,
• Kerstin Hesidens and
• Jürgen Kolz

Beilstein J. Org. Chem. 2009, 5, No. 71, doi:10.3762/bjoc.5.71

• report on the total synthesis of compounds which possess more rigid two-carbon biaryl bridges like stilbene (E or Z) or even tolane moieties which were introduced starting with a Sonogashira protocol. The McMurry method proved to be a powerful tool for the cyclization to these considerably ring-strained

• conformational analysis and MD investigations clearly confirmed the biaryl axis A to be configurationally stable at room temperature due to the second (more flexible) biaryl axis B, an (even more flexible) helical stilbene unit C and their combination with the ring-strain of the entire molecule. By experimental

• (2) and C (1) possess two saturated ethylene bridges (between rings a–d and b–c) or just one cis-configurated double bond (’stilbene bridge’) between rings a–d. From a structural as well as a synthetic point of view we were interested in compounds which possess various unsaturated stilbene (E or Z

The development and evaluation of a continuous flow process for the lipase- mediated oxidation of alkenes

• Charlotte Wiles,
• Marcus J. Hammond and
• Paul Watts

Beilstein J. Org. Chem. 2009, 5, No. 27, doi:10.3762/bjoc.5.27

• -oxide at 70 °C, 2.6 min residence time, and was isolated in 97.6% yield. In addition to evaluation of aromatic and aliphatic alkenes discussed, the epoxidation of cis-stilbene (11) and trans-stilbene (12) was investigated (Scheme 4). Due to the molecule’s symmetry, the configuration of the epoxides

• peracid, enabling greater system flexibility, along with evaluating the methodology towards other synthetically useful oxidations. Experimental Materials 1-Methylcyclohexene (6, 99%, Aldrich), styrene (9, ReagentPlus®, ≥ 99%, Aldrich), cis-stilbene (11, 96%, Aldrich), trans-stilbene (12, 96%, Aldrich

• ), cis-stilbene (11) and trans-stilbene (12) were analysed using the following method; injector temperature 200 °C, carrier gas flow rate 1.00 ml min−1, oven temperature 50 °C for 4 min then ramped to 150 °C at 30 °C min−1 and held at 150 °C for 6.17 min, with a 2.5 min filament delay. Mass spectrometry

The vicinal difluoro motif: The synthesis and conformation of erythro- and threo- diastereoisomers of 1,2-difluorodiphenylethanes, 2,3-difluorosuccinic acids and their derivatives

• David O'Hagan,
• Henry S. Rzepa,
• Martin Schüler and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2006, 2, No. 19, doi:10.1186/1860-5397-2-19

• these results have recently been communicated [18]. The study suggests that the vicinal fluorine gauche effect can have a significant influence on the conformation of the 1,2-difluorosuccinates. Results and Discussion Synthesis of erythro- and threo- 1,2-diphenyl-1,2-difluoroethanes 13 Stilbene 9 is

• benzylic as well as anchimeric stabilisation via phenonium ring formation 18 with the β-phenyl group as illustrated in Scheme 6. Isolation of the minor threo-13 isomer required careful chromatography. In order to improve the synthesis of threo-13 a reaction with cis-stilbene 17 was investigated. The one

• ]. Halofluorination of electron-rich alkenes with in situ fluoride displacement generates vicinal difluoro products. PPHF is Olah's reagent, pyridinium poly(hydrogen fluoride) [15]. Bromofluorination of stilbene [19]. Treatment of anti-14 with base generated the E-fluorostilbene 15 by an anti elimination mechanism

Hydrogenation of aromatic ketones, aldehydes, and epoxides with hydrogen and Pd(0)EnCat™ 30NP

• Steven V. Ley,
• Angus J. P. Stewart-Liddon,
• David Pears,
• Remedios H. Perni and
• Kevin Treacher

Beilstein J. Org. Chem. 2006, 2, No. 15, doi:10.1186/1860-5397-2-15

• were obtained. The results are summarized in Table 2. trans-Stilbene oxide was chosen as a model for the hydrogenolysis of aromatic epoxides. The effect of different heterogeneous palladium catalysts and their propensity to over-reduce the benzylic alcohol generated after hydrogenolysis of the epoxide

• or Pd/Al2O3. Pd(0)EnCat™ 30NP-catalyzed hydrogenation of 4-mathoxybenzaldehyde and 4-methoxyacetophenone. Comparison with other Pd catalysts. Pd(0)EnCat™30NP-catalyzed hydrogenation of aryl ketones and aldehydes. Pd(0)EnCat™ 30NP-Catalyzed Hydrogenolysis of trans-stilbene oxide. Comparison with other