Natural phenolic metabolites with anti-angiogenic properties – a review from the chemical point of view

• Qiu Sun,
• Jörg Heilmann and
• Burkhard König

Beilstein J. Org. Chem. 2015, 11, 249–264, doi:10.3762/bjoc.11.28

• . Resveratrol Resveratrol (8) is a natural polyphenol that belongs to the stilbene-type compounds and exists in a large number of plants. It has been primarily extracted from grape (Vitis vinifera L., Vitaceae) and mulberry (Morus L., Moraceae) fruits (Figure 4) [34]. It has antioxidant effects, anti-estrogenic

Photochemical approach to functionalized benzobicyclo[3.2.1]octene structures via fused oxazoline derivatives from 4- and 5-(o-vinylstyryl)oxazoles

• Ivana Šagud,
• Simona Božić,
• Željko Marinić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2014, 10, 2222–2229, doi:10.3762/bjoc.10.230

• electrocyclization of the benzodivinyl moiety to intermediate C followed by 1,5-H shift and rearomatization of the benzene ring. Analogue electrocyclization was not detected in phenyl or furyl-substituted o-divinylbenzenes but instead stilbene-like 6π electrocyclization and formation of 1-vinylphenanthrene [42] or 6

Direct C–H trifluoromethylation of di- and trisubstituted alkenes by photoredox catalysis

• Ren Tomita,
• Yusuke Yasu,
• Takashi Koike and
• Munetaka Akita

Beilstein J. Org. Chem. 2014, 10, 1099–1106, doi:10.3762/bjoc.10.108

• photocatalytic reaction can be tolerant of the Boc-protected amino group (2f) or pyridine (2h). Moreover, a substrate with an alkyl substituent, 2,4-diphenyl-4-methyl-1-pentene (2i), was also applicable to this transformation, whereas the reaction of 1,2-disubsituted alkenes such as trans-stilbene provided

Visible-light photoredox catalysis enabled bromination of phenols and alkenes

• Yating Zhao,
• Zhe Li,
• Chao Yang,
• Run Lin and
• Wujiong Xia

Beilstein J. Org. Chem. 2014, 10, 622–627, doi:10.3762/bjoc.10.53

• could be prepared from the same starting materials in two steps (Table 2). We also conducted a control experiment by reacting stilbene with CBr4 (1 equiv) in dry CH3CN in the presence of Ru(bpy)3Cl2 (5.0 mol %) with visible-light irradiation (blue LEDs, λmax = 435 nm) for 72 hours, which led to the anti

• -1,2-dibromo-1,2-diphenylethane in 92% yield. This result is in accordance with the direct bromination of stilbene from liquid bromine [47]. Based on this result, our protocol provides an easily manageable and environment-friendly pathway to the bromination of alkenes. We further examined the scope of

Continuous flow photocyclization of stilbenes – scalable synthesis of functionalized phenanthrenes and helicenes

• Quentin Lefebvre,
• Marc Jentsch and
• Magnus Rueping

Beilstein J. Org. Chem. 2013, 9, 1883–1890, doi:10.3762/bjoc.9.221

• Quentin Lefebvre Marc Jentsch Magnus Rueping Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany 10.3762/bjoc.9.221 Abstract A continuous flow oxidative photocyclization of stilbene derivatives has been developed which allows the scalable synthesis of

• of scalable and flexible syntheses [1][2][3][4][5]. Following the pioneering examples of Scholz [6] and Martin [7] in 1967, the photocyclization of stilbene derivatives under UV-light irradiation is now a classical method for the synthesis of phenanthrenes and helicene-like molecules [8]. However

• the efficiency of the transformation is no longer related to the scale [17][18][19][20][21]. Therefore, the development of an efficient protocol for the photocyclization of stilbene derivatives in flow would be of great interest. A recent contribution described the flow-synthesis of [5]helicene under

Cyclization of substitued 2-(2-fluorophenylazo)azines to azino[1,2-c]benzo[d][1,2,4]triazinium derivatives

• Aleksandra Jankowiak,
• Emilia Obijalska and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2013, 9, 1873–1880, doi:10.3762/bjoc.9.219

• cyclization process involves 6 π electrons, which allows the formation of the non-zwitterionic product such as 10. Comparison of cyclization of 4c-Z and 13-Z further demonstrates that the activation energy is lower for the azene than for the analogues stilbene, which presumably is related to the

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

• Ping-An Wang

Beilstein J. Org. Chem. 2013, 9, 1677–1695, doi:10.3762/bjoc.9.192

• desymmetrization of meso-epoxides by SiCl4. In the presence of 1.5 equiv of iPr2NEt, various acyclic and cyclic meso-epoxides were desymmetrized to enantioenriched chlorohydrins (96 to 101) in high yields (Scheme 16). When meso-stilbene oxide was used as a substrate, the best enantioselectivity was up to 90% ee

• phosphine oxides OC-64 and OC-69 for the enantioselective desymmetrization of meso-stilbene oxide to provide the corresponding vicinal chlorohydrin 96 in up to 82% ee. More recently, Ready [86] and co-workers have synthesized a series of chiral phosphine oxides (OC-70 to OC-77) based on an allene backbone

• reactive and enantioselective catalyst to produce the chlorohydrins in up to 94% ee with only 0.1 mol % catalyst-loading. The cis-stilbene oxides with substituent in the meta or para position are tolerated, the yields and enantioselectivities of desired chlorohydrins are satisfying, but ortho-substituted

Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

• Tanveer Mahamadali Shaikh and
• Fung-E Hong

Beilstein J. Org. Chem. 2013, 9, 1578–1588, doi:10.3762/bjoc.9.180

• Substituted olefins are important structural motifs in natural products, pharmaceuticals, bioactive compounds and organic materials [1][2]. Olefins such as stilbene derivatives normally show antitumor [3], antiinflammatory [4], neuroprotective [5], and cardioprotective [6] properties. Due to its importance in

• % yield (Table 1, entry 6). The yield was slightly improved when the reaction was heated at 60 °C (Table 1, entry 7). When K2CO3 (1.0 equiv) in THF was employed under similar reaction conditions, the yield of trans-stilbene was improved to 46% (Table 1, entry 8). Once K2CO3 had been selected as the most

• formed in situ, thus lowered the yield of the product. Therefore, the loading of the precatalyst 6 was increased to 2 mol % and resulted in the formation of trans-stilbene in 92% yield at 80 °C (Table 1, entry 11). Synthetically, it is important to carry out reactions under mild reaction conditions

Amyloid-β probes: Review of structure–activity and brain-kinetics relationships

• Todd J. Eckroat,
• Abdelrahman S. Mayhoub and
• Sylvie Garneau-Tsodikova

Beilstein J. Org. Chem. 2013, 9, 1012–1044, doi:10.3762/bjoc.9.116

• resulted in a variety of radiolabeled molecular probes for in vivo PET/SPECT imaging. The scaffolds from which these newer radiolabeled probes are derived include chalcone (5) and its conformationally restricted analogues flavone (6) and aurone (7); stilbene (8) and its analogues diphenyl-1,2,4-oxadiazole

• chalcone and flavone derivatives, [Re]- and [99mTc]-labeled aurone complexes 33a and 33b were also prepared [18]. The high affinity for Aβ aggregates observed with the [99mTc]-labeled aurone 33b was hampered by its weak brain penetration, which made it unsuitable for in vivo application [18]. Stilbene and

• its analogues Stilbene derivatives The SARs of stilbene analogues, such as 44a–f, 45, and 46a,b (Scheme 4A), as Aβ plaque tracers have been thoroughly investigated. In general, it was found that an electron-donating group at each end of the stilbene derivative is essential for Aβ plaque binding

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

Cyclodextrin-induced host–guest effects of classically prepared poly(NIPAM) bearing azo-dye end groups

• Gero Maatz,
• Arkadius Maciollek and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 1929–1935, doi:10.3762/bjoc.8.224

• Polymers bearing dyes, such as azo, stilbene, anthraquinone or fluorescence dyes, in the main or side chain have been widely described and investigated [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. A few examples of dyes located at the end group of polymers are prepared preferably under anionic or

• ]. Several reports are available on the preparation and properties of thermally responsive polyacrylamides containing azobenzene or stilbene dyes in the side chain [3][14]. Furthermore, the interaction of dye-containing polymers with CD in water is of some interest, because of their external, light-induced

Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates

• Rick C. White,
• Benny E. Arney Jr. and
• Heiko Ihmels

Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134

• harsher conditions, the original experimental conditions (t = 15 h) were changed. Thus irradiation of 9 in CH3CN for 120 min gave 5 and 6, along with the so far undetected products 3b, benzaldehyde (12), cis-stilbene (10) and phenanthrene (11). The same products were found after irradiation in cyclohexane

• tetraphenylethylene, the latter has not been detected [16]. The formation of 10 may be explained by the additional phenyl substituent, as compared to the cyclic sulfite 8, which apparently facilitates the elimination of SO3 to give stilbene (10). Firstly, the phenyl substituent leads to a significant stabilization of

•  3). The cis-stilbene (10) is subsequently transformed into phenanthrene (11) by photoinduced electrocyclization [22] as shown in Scheme 4. Conclusion We have demonstrated that the performance of photoreactions of cyclic sulfites under relatively mild reaction conditions enables the detection of

Highly selective synthesis of (E)-alkenyl-(pentafluorosulfanyl)benzenes through Horner–Wadsworth–Emmons reaction

• George Iakobson and
• Petr Beier

Beilstein J. Org. Chem. 2012, 8, 1185–1190, doi:10.3762/bjoc.8.131

• ][21][22]. Alkenyl substituted SF5-benzenes or SF5-containing stilbene derivatives are not known and would represent basic synthetic intermediates towards more elaborate structures. We envisioned a synthetic route towards these compounds through Horner–Wadsworth–Emmons (HWE) reaction of phosphonates 3

• successful attempts have been made to favor Z-alkenes [26][27][28]. Results and Discussion The HWE reaction of phosphonate 3 with benzaldehyde in the presence of a base giving stilbene derivative 5a was investigated. At first, attempts were made to form 5a directly from 1 and diethyl chloromethylphosphonate

• 11d in good yield (Scheme 4). To avoid problems with alkene reduction and electrophilic aromatic substitution during nitro group removal, we decided to try a different approach to the general synthesis of SF5-containing stilbene derivatives, as demonstrated in the synthesis of 13d shown in Scheme 5

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• UV–vis absorption spectrum of azobenzene presents two characteristic absorption bands corresponding to π→π* and n→π* electronic transitions. The transition π→π* is usually in the near UV region and is common to carbonate systems, such as stilbene [18]. The electronic transition n→π* is usually

• and S2←S0 excitations and cis–trans isomerization by exciting into the S1 or S2 state [21]. The sum of the quantum yields is different to unity, which indicates multiple pathways for isomerization. In stilbene, the isomerization occurs exclusively by rotation and the quantum yield equals unity [22

• type (o- or p-(X)–C6H4–N=N–Ar): The π→π* and n→π* bands are very close or collapsing in the UV–vis region. In this case, the azocompounds have electron-donor substituents (X) in the ortho or para positions (orange colour). Pseudo-stilbene type [(X)–C6H4–N=N–C6H4–(Y)]: The absorption band corresponding

Liquid-crystalline nanoparticles: Hybrid design and mesophase structures

• Gareth L. Nealon,
• Romain Greget,
• Cristina Dominguez,
• Zsuzsanna T. Nagy,
• Daniel Guillon,
• Jean-Louis Gallani and
• Bertrand Donnio

Beilstein J. Org. Chem. 2012, 8, 349–370, doi:10.3762/bjoc.8.39

• to emphasise the wider applicability of this approach to nanohybrid science. Fundamental studies into the photochemical activity of lipophilic azobenzene- and stilbene thiols (10, Figure 12) on Au NPs surfaces were reported [66], which indicated a chromophore-to-NP distance dependence of the

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis

• Kristina Butković,
• Željko Marinić,
• Krešimir Molčanov,
• Biserka Kojić-Prodić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2011, 7, 1663–1670, doi:10.3762/bjoc.7.196

• Abstract New trans- and cis-o-stilbene-methylene-sydnones 3a,b were synthesized by transforming the trans- and cis-o-aminomethylstilbene derivative, obtained by reduction of corresponding o-cyano derivatives, into glycine ester derivatives (43 and 31% yield) followed by hydrolysis (90 and 96% yield

• remaining in the structure [18]. We have been studying photochemical reactions of conjugated heterostilbene derivatives in which the sydnone moiety is part of a heterostilbene [17] (1, Figure 3) or is directly attached at the ortho position to the stilbene 2 [21][22][23]. Upon photolysis of compound 1

• result of competitive photolysis of the sydnone moiety was confirmed on irradiation of 1 in the presence of acrolein and isolation of the pyrazoline derivative (F, Figure 3) [17]. In the case of stilbenylsydnones 2, where the sydnone moiety is directly connected to the ortho position of the stilbene, the

Directed ortho,ortho'-dimetalation of hydrobenzoin: Rapid access to hydrobenzoin derivatives useful for asymmetric synthesis

• Inhee Cho,
• Labros Meimetis,
• Lee Belding,
• Michael J. Katz,
• Travis Dudding and
• Robert Britton

Beilstein J. Org. Chem. 2011, 7, 1315–1322, doi:10.3762/bjoc.7.154

• (S,S)-hydrobenzoin are relatively inexpensive [18], or can be readily prepared on kilogram-scale from trans-stilbene through Sharpless asymmetric dihydroxylation (SAD) [19][20], the synthesis of ortho,ortho'-functionalized derivatives of hydrobenzoin typically requires several steps that include

• McMurry coupling of an ortho-substituted benzaldehyde followed by I2-catalyzed isomerization of the resulting stilbene and subsequent SAD [21][22]. Thus, while various hydrobenzoin derivatives have been reported, their multi-step synthesis, the modest enantioselectivity in the SAD step [22], the problems

Continuous flow hydrogenation using polysilane-supported palladium/alumina hybrid catalysts

• Hidekazu Oyamada,
• Takeshi Naito and
• Shū Kobayashi

Beilstein J. Org. Chem. 2011, 7, 735–739, doi:10.3762/bjoc.7.83

• double and triple bonds in various substrates are shown in Table 1; these proceeded quantitatively at room temperature under neat conditions. The products were obtained at approximately 10 g/h through the 4 cm3 column. The hydrogenation reactions of trans-stilbene and trans-chalcone, as representative

• solid substrates (Scheme 2), were also examined. The substrates were dissolved in toluene or ethyl acetate. The reduction of trans-stilbene proceeded quantitatively, but an overreaction product was obtained (7% yield) in the reduction of trans-chalcone. We then investigated the hydrogenation of a nitro

• , CDCl3) δ 1.24 (t, J = 7.7 Hz, 3H), 2.65 (q, J = 7.7 Hz, 2H), 7.15–7.23 (m, 3H), 7.26–7.30 (m, 2H). Hydrogenation reaction of trans-stilbene (Scheme 2): trans-Stilbene (Aldrich) in toluene (0.25 M) was fed into the column (maintained at 40 °C in a water bath) using the HPLC pump (1.0 mL/min), and H2 gas

When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• -deficient olefins, via charged intermediates, under simple thermal conditions [37]. In contrast to the behaviour of cyclopropenone acetal 3, Toste et al. observed that the reaction of the 3,3-disubstituted cyclopropene 47 and (Z)-stilbene in the presence of a cationic gold catalyst could effectively provide

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• -1 and COX-2. The central ring is usually a five-membered aromatic system, which is diaryl-substituted with a (Z)-stilbene-like linking structure. A polar sulfonamide group or biologically equivalent unit is usually present at the para-position of one of the aryl rings and is believed to promote

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