Solid-phase enrichment and analysis of electrophilic natural products

• Frank Wesche,
• Yue He and
• Helge B. Bode

Beilstein J. Org. Chem. 2017, 13, 405–409, doi:10.3762/bjoc.13.43

• . Results and Discussion In order to evaluate whether the CARR approach is suitable for epoxide detection, we azidated commercially available trans-stilbene oxide as representative model compound for 1 affording the vicinal azido alcohol, 2-azido-1,2-diphenylethanol (Supporting Information File 1, Figure S2

• amounts of trans-stilbene oxide were added to liquid Lysogeny Broth (LB) medium. The obtained methanolic Amberlite XAD-16 extracts were azidated, enriched and analyzed. Up to a final concentration of 5 µg/L (≈25 nmol/L) the epoxide could be detected (Supporting Information File 1, Figure S4). Following

• these results, we tested the method with an XAD extract of P. luminescens TT01 (Figure 1). The obtained XAD extract was treated the same way as trans-stilbene oxide, and any potentially containing epoxide should be converted into the corresponding vicinal azido alcohol. Afterwards the azidated extract

Symmetry-based approach to oligostilbenoids: Rapid entry to viniferifuran, shoreaphenol, malibatol A, and diptoindonesin G

• Youngeun Jung,
• Dileep Kumar Singh and
• Ikyon Kim

Beilstein J. Org. Chem. 2016, 12, 2689–2693, doi:10.3762/bjoc.12.266

• . Keywords: anticancer agent; iodocyclization; natural product; oligostilbenoids; Pd-catalyzed coupling; Introduction Oligostilbenoids constitute a family of natural products with various biological functions (Figure 1). Monomeric stilbene units are interconnected in a number of ways to lead to complex

Selectively fluorinated cyclohexane building blocks: Derivatives of carbonylated all-cis-3-phenyl-1,2,4,5-tetrafluorocyclohexane

• Mohammed Salah Ayoup,
• David B. Cordes,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2015, 11, 2671–2676, doi:10.3762/bjoc.11.287

• a mixture of stilbene isomers 16. Direct hydrogenation of the mixture afford dihydrostilbene 17 as a crystalline solid, a structure which was confirmed by X-ray crystallography and is shown in the inset in Scheme 3. Aldehyde 15 could also be converted to styrene 18 in good yield using the Simmons

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• , the addition of amino additives such as pyridine, morpholine, Et3N or DBU was shown to be detrimental to the G-HII-catalyzed dimerization of styrene (Table 2). Moderate to poor yields in stilbene 7’ were obtained and the value of the yields was correlated with the pKa of the couple ammonium/amine. An

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

• ) under basic conditions to generate compound 42 which was further subjected to a Glaser–Eglinton coupling to deliver cyclophane 43 (Scheme 5). A derivative of compound 43 was used as a host for compounds such as 6-nitro-2-naphthol, stilbene derivatives and serotonin mimics. This paper depicts the edge

• ) [104][105][106]. Among the π-conjugated systems stilbene derivatives found a unique place in materials science due to their optical and charge conducting properties. Tsuge and co-workers [107] reported the synthesis of stilbene 88 by using the McMurry coupling and studies on the transmission of the

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