Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• was obtained, e.g., when simple stilbene was used the reaction led to only traces of product 194 (Scheme 33). With benzoxazole-conjugated alkenes, upon treatment with catalytic Cu complexed by a nonracemic Josiphos ligand (L20), good chemical yields of the desired enantioenriched products 196–199

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• involved in the reaction. Excellent yields of products 3a or 5a were obtained in the presence of the radical scavengers (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), stilbene, or butylated hydroxytoluene (BHT) in the reaction of benzyl bromide with 2-methyl-2-oxazoline or 2-(methylthio)-4,5

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• synthesized in 57% yield. Importantly, the reaction scale was increased to 1 g under continuous flow conditions. Then, the reaction was extended to the cyclization of a stilbene derivative into phenanthrene in a moderate 23% isolated yield. To explain the reaction pathway, the authors suggested an oxidative

Potent hemithioindigo-based antimitotics photocontrol the microtubule cytoskeleton in cellulo

• Alexander Sailer,
• Franziska Ermer,
• Yvonne Kraus,
• Rebekkah Bingham,
• Ferdinand H. Lutter,
• Julia Ahlfeld and
• Oliver Thorn-Seshold

Beilstein J. Org. Chem. 2020, 16, 125–134, doi:10.3762/bjoc.16.14

• the stilbene combretastatin, and the torsion angle between the aryl blades of the HTI is nearly planar (up to 4°), while that between the rings of (Z)-combretastatin or colchicine is approximately 50–60° [20]. Thus, we assumed that the length and the near-planarity of the HTI could suit it to

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• attempts have also been made to develop photochromic DNA binders. Thus, it has been shown with spiropyran [19][20][21], stilbene [22][23], azobenzene [24][25][26][27][28], dithienylethene [29][30][31][32], chromene [33], and spirooxazine [34] derivatives that specifically modified photochromic ligands bind

• stilbene derivatives as photoswitchable DNA ligand [35], and in this case, the structure of the photoproduct was not fully identified. Also, it has been shown that a DNA-binding azoniatetracene may be generated by photoinduced [4 + 4] cycloreversion. However, this system was not applied for photoinduced

• deactivation of a stilbene tyrosine kinase inhibitor by a [2 + 2] photocycloaddition [59]. As the quinolizinium ion has been established as a versatile platform for the development of DNA intercalators [60], we identified styryl-substituted quinolizinium derivatives as a promising basis for the search for

Effect of ring size on photoisomerization properties of stiff stilbene macrocycles

• Sandra Olsson,
• Óscar Benito Pérez,
• Magnus Blom and
• Adolf Gogoll

Beilstein J. Org. Chem. 2019, 15, 2408–2418, doi:10.3762/bjoc.15.233

• Sandra Olsson Oscar Benito Perez Magnus Blom Adolf Gogoll Department of Chemistry-BMC, Uppsala University, S-751 23 Uppsala, Sweden Faculty of Chemistry, Universitat de Barcelona, C/ Martí i Franquès 1, 08028 Barcelona, Spain 10.3762/bjoc.15.233 Abstract A series of stiff stilbene macrocycles

• have been studied to investigate the possible impact of the macrocycle ring size on their photodynamic properties. The results show that reducing the ring size counteracts the photoisomerization ability of the macrocycles. However, even the smallest macrocycle studied (stiff stilbene subunits linked by

• largest macrocycle (linked by a twelve carbon chain) is significantly higher than that of the stiff stilbene unit itself. In general, it is indicated that addition of even a flexible chain to the stiff stilbene unit may significantly affect its photochemical properties and increase the photostability of

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• bioactivity, allows the probing of pharmacologically relevant systems with spatiotemporal resolution. A hetero-stilbene lead resulting from the screening of a compound that was originally designed as kinase inhibitor served as a starting point for the design of photoswitchable sirtuin inhibitors. Because the

• has been studied intensely in the past [19][20][21][22][23]. Due to the multifaceted photoreactivity of unsubstituted stilbenes, an appropriate modification of the stilbene core is necessary to prevent unwanted irreversible side reactions [24][25]. On the contrary, the photochemical properties of

• inhibitors has already been fruitful in the past [32][33]. Therefore, a focused kinase inhibitor library from GlaxoSmithKline was screened for biological activity on human sirtuin isoforms Sirt1–Sirt3. Aza-stilbene derivative GW435821X (2a, Figure 1), initially published as c-RAF kinase inhibitor, was

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

• Esther Nieland,
• Oliver Weingart and
• Bernd M. Schmidt

Beilstein J. Org. Chem. 2019, 15, 2013–2019, doi:10.3762/bjoc.15.197

• stilbene squares used for topochemical polymerization [22]. Additionally, halonium ions [N···I+···N] were reported to form several charged, discrete supramolecular capsules [30][31][32][33] and helicates [34]. In the same line, we have demonstrated recently that both E-4,4’-di(iodo)perfluoroazobenzene (A2

Synthesis of a [6]rotaxane with singly threaded γ-cyclodextrins as a single stereoisomer

• Jason Yin Hei Man and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2019, 15, 1829–1837, doi:10.3762/bjoc.15.177

• threaded through an α-CD [16]. The corresponding rotaxane with a β-CD was obtained in lower yield, probably due to a weaker binding of the alkyl group to β-CD as a result of a size mismatch [17]. For β-CD with a larger cavity, interlocked molecules derived from aromatic units such as biphenyl, stilbene

• [32][33][34][35][36]. By adopting a stepwise stoppering approach, Anderson and co-workers have synthesized a [3]rotaxane consisting of two different axles, derived from a stilbene and a cyanine, threaded through one γ-CD [33]. Inouye has also reported a [3]rotaxane with two pyrene-derived axles

Photochemical generation of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical from caged nitroxides by near-infrared two-photon irradiation and its cytocidal effect on lung cancer cells

• Ayato Yamada,
• Manabu Abe,
• Yoshinobu Nishimura,
• Shoji Ishizaka,
• Masashi Namba,
• Taku Nakashima,
• Kiyofumi Shimoji and
• Noboru Hattori

Beilstein J. Org. Chem. 2019, 15, 863–873, doi:10.3762/bjoc.15.84

• -responsive photo-labile protecting group [56][57][58] with simple cyclic stilbene structures such as 2-(4-nitrophenyl)benzofuran (NPBF) that absorb in the NIR region of 710–760 nm for the uncaging of bioactive substances such as glutamate and Ca2+ [59][60][61][62][63][64]. Herein, we report the synthesis of

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• the catalysts (1.0, 0.1 and 0.01 mol %) were applied for the transformation of styrene (12) to trans-stilbene (13) by cross-metathesis reaction (Scheme 6). First experiments (entries 1–4, Table 3) revealed that the nonpolar solvents (PhH and PhMe) are not suitable for the CM reactions. Using of 1 mol

• % of catalyst 11a even under an argon atmosphere produced only traces of the target stilbene (13). In these conditions, catalyst 11b was more active than 11a, but also gave insufficient results. Thereupon, these two solvents were also abandoned in the course of the following investigations. In this

• catalysts 11a–c (Figure 3). In spite of the fact that we do not have the X-ray analysis for catalyst 11d, it is possible to assume that this complex should exhibit the longest coordination N→Ru bond (at least more than 2.30 Å). Interestingly, lower yields of stilbene from styrene in CH2Cl2 were obtained in

Synthesis of the aglycon of scorzodihydrostilbenes B and D

• Katja Weimann and
• Manfred Braun

Beilstein J. Org. Chem. 2019, 15, 610–616, doi:10.3762/bjoc.15.56

• = R2 = H, instead of β-glycosyl, respectively). Results and Discussion Most syntheses of dihydrostilbenes rely on a carbonyl olefination followed by hydrogenation of the stilbene [7][8][9]. However, this route appeared not attractive, particularly as our attempts to hydrogenate highly substituted

Cross metathesis-mediated synthesis of hydroxamic acid derivatives

• Shital Kumar Chattopadhyay,
• Subhankar Ghosh and
• Suman Sil

Beilstein J. Org. Chem. 2018, 14, 3070–3075, doi:10.3762/bjoc.14.285

• derivatives, belonging to class-I olefins according to Grubbs’ generalizations [31], are indeed known to be a sluggish partner in CM reactions, with homodimerization to stilbene being a recurring problem. Alkenes 4h–j containing a benzyl ester functionality at two, three and four carbons apart, respectively

A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts

• Daniel S. Müller,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2018, 14, 2999–3010, doi:10.3762/bjoc.14.279

• stilbene formation. Replacing styrenes by (Z)-β-methylstyrenes (e.g., 32) allowed for successful reactions with methyl ester 33 (Scheme 6a). Hoveyda noted that carboxylic acids (e.g., 34) are not suitable cross-metathesis partners for (Z)-β-methylstyrenes. Hoveyda reasoned that with the sluggishly reacting

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• Diarylethenes (DAEs) are a rich family of organic photoswitches formally derived from stilbene [1][2]. Upon irradiation they are able to undergo reversible photoisomerization based on 6π-electrocyclization and -cycloreversion, respectively, between two thermally stable states, which make them interesting

• the double bond geometry. Since ring-closure requires the two reactive α-thienyl carbon atoms to approach each other, presumably an additional electrochemically induced E → Z isomerization occurs prior to cyclization. Indeed, there are scattered reports about configurational isomerism in stilbene

• reduction of the E-isomer is reversible. This behavior differs strongly from that of stilbene, in which reduction occurs at the double bond and causes an equilibration of the double bond isomers in favor of the E-stilbene [49]. Conclusion We have investigated the electrochemical behavior of sDTEs, a new

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• , Suzuki coupling of 79 with diverse arylboronic acids (e.g., phenylboronic acid (36)) gave a highly substituted naphthoxepine derivative 80 (90%) (Scheme 12). Stilbene derivatives Hoveyda and co-workers [44] reported the synthesis of Z-(pinacolato)allylboron and Z-(pinacolato)alkenylboron derivatives via

• CM by using Mo complex 6. In this regard, they assembled stilbene derivative 85 as an antitumor agent by a two-step strategy that involve catalytic CM and SM coupling. To this end, the Z-selective CM of a styrene derivative (e.g., 81) with vinyl-B(pin) 82 was realized in the presence of Mo complex 6

• to provide a highly substituted vinyl-B(pin) 83 (73%) with excellent selectivity (96:4 Z:E). Further, vinylboron compound 83 was subjected to SM coupling with a suitable partner (e.g., 84) to afford the stilbene derivative 85 (96:4 Z:E) in 74% yield (Scheme 13). Majchrzak and co-workers [45

One-pot synthesis of epoxides from benzyl alcohols and aldehydes

• Edwin Alfonzo,
• Jesse W. L. Mendoza and
• Aaron B. Beeler

Beilstein J. Org. Chem. 2018, 14, 2308–2312, doi:10.3762/bjoc.14.205

• benzyl alcohols and aldehydes. Scope of the reaction with electron-rich alcohols and aldehydes. One-pot synthesis of epoxides from benzyl alcohols and aldehydes. mCPBA epoxidation of electron-rich stilbene derivatives. Supporting Information Supporting Information File 398: Experimental procedures and

Hypervalent iodine compounds for anti-Markovnikov-type iodo-oxyimidation of vinylarenes

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Mikhail A. Syroeshkin,
• Alexander A. Korlyukov,
• Pavel V. Dorovatovskii,
• Yan V. Zubavichus,
• Gennady I. Nikishin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2018, 14, 2146–2155, doi:10.3762/bjoc.14.188

• styrene (1i) and (E)-stilbene (1j) also underwent the studied transformation giving iodo-oxyimides 3ia (yield 51%) and 3ja (yield 83%). The reaction of NHPI (2a) with p-methoxystyrene under standard conditions led to a complex mixture of products, possibly due to an increased tendency of the substrate to

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• by the same group and its utility in the enantioselective ring-opening of cis-stilbene oxide with aniline and thiophenol was demonstrated. The reaction provided the corresponding β-hydroxy derivatives in good yields and excellent enantioselectivities (Scheme 15) [49]. Bipyridine as a scaffold in

• ligand design was also adopted by Chen and Chen, who reported the bipyridine-pinene ligand 57 in combination with Ti(O-iPr)4 as an effective catalyst in the asymmetric ring opening of meso-stilbene oxides with thiophenol, in acetonitrile as the solvent, for 30 hours, at room temperature under a nitrogen

• complex. Enantioselective ring-opening reaction of stilbene oxides with ArSH catalyzed by a C2-symmetric chiral bipyridyldiol–titanium complex. Asymmetric desymmetrization of meso-epoxides using BINOL-based Brønsted acid catalysts. Lithium-BINOL-phosphate-catalyzed desymmetrization of meso-epoxides with

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• , including quinolyl and benzoyl derivatives, and alkenes as linkers in order to investigate their antimicrobial properties [58][59]. One of these structural analogs, MGB-BP-3 (Figure 4), containing a stilbene like fragment as head group and two N-methylpyrroles attached to an aminoethylmorpholine as tail

Liquid-assisted grinding and ion pairing regulates percentage conversion and diastereoselectivity of the Wittig reaction under mechanochemical conditions

• Kendra Leahy Denlinger,
• Lianna Ortiz-Trankina,
• Preston Carr,
• Kingsley Benson,
• Daniel C. Waddell and
• James Mack

Beilstein J. Org. Chem. 2018, 14, 688–696, doi:10.3762/bjoc.14.57

• present, its dielectric constant will be the determining factor in diastereoselectivity, consistent with our previous observations. Counter-ion pairing We further hypothesized that, if the benzyl benzoate is formed through a six-membered ring intermediate to give (E)-stilbene as the major product, then

• halides (Table 4). Pairing of a hard acid (Li+ or Na+) with a moderately soft base (Br−) leads to no or poor conversion to stilbene products. Conversely, the best conversion resulted when combining Cs+ (soft acid) with Br− (borderline soft base). The benzyl benzoate side-product observed in trials 1, 2

• , and 5 indicates that the carbonate bases deprotonated the phosphonium salt to form the ylide which then subsequently added to the benzaldehyde. However, the oxygen anion could not bind to the phosphorus cation to produce the stilbene product, presumably due to the mismatched counter ion pair. After

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• % of PCy3·HBF4 along with an excess K2CO3–MeOH led to biaryls within 99 min and with a yield up to 97% (Scheme 8) [57]. Heck reaction Frejd and co-workers reported the first mechanochemical Heck reaction [58]. Su and co-workers demonstrated that (E)-stilbene derivatives were synthesized by the coupling

An efficient Pd–NHC catalyst system in situ generated from Na₂PdCl₄ and PEG-functionalized imidazolium salts for Mizoroki–Heck reactions in water

• Nan Sun,
• Meng Chen,
• Liqun Jin,
• Wei Zhao,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 1735–1744, doi:10.3762/bjoc.13.168

• -vinylpyridine (2g), as well as an internal alkene ((E)-stilbene, (2h)). To our delight, all these tested alkenes smoothly transformed into the corresponding products 3ab–ah in excellent yields (85–97%) with 0.05–0.1 mol % of Na2PdCl4/L1 at 100 or 120 °C (Table 3). It is noteworthy that a trace amount of 1,1

An effective Pd nanocatalyst in aqueous media: stilbene synthesis by Mizoroki–Heck coupling reaction under microwave irradiation

• Carolina S. García,
• Paula M. Uberman and
• Sandra E. Martín

Beilstein J. Org. Chem. 2017, 13, 1717–1727, doi:10.3762/bjoc.13.166

• make this protocol a great option for stilbene syntheses by Mizoroki–Heck reaction. Keywords: aqueous reaction medium; MAOS; Mizoroki–Heck reaction; Pd nanoparticle; sustainable organic synthesis; Introduction Palladium-catalyzed reactions have emerged as an important tool for organic synthesis

• - or 4-bromoacetophenone and styrene [47]. The best result with 4-bromoacetophenone was accomplished when the reaction was performed under MW irradiation for 10 minutes using 0.2 mol % of Pd, affording the (E)-stilbene product in 98% yield. In order to further explore the scope of the PVP-Pd NPs

• )). In a first approach, time optimization was performed by using K2CO3 as base, at 130 °C by MW irradiation (entries 1–3, Table 1). The highest catalytic activity of PVP-Pd NPs was obtained after 10 minutes, when the yield of stilbene 3 achieved 100% (entry 3, Table 1). Reducing the catalyst loading

Photocatalyzed synthesis of isochromanones and isobenzofuranones under batch and flow conditions

• Manuel Anselmo,
• Lisa Moni,
• Hossny Ismail,
• Davide Comoretto,
• Renata Riva and
• Andrea Basso

Beilstein J. Org. Chem. 2017, 13, 1456–1462, doi:10.3762/bjoc.13.143

• afforded isochromanone 4a in 71% yield upon reaction with methyl methacrylate under the previously developed conditions. Similarly, compounds 4b–k were synthesized under the same conditions, with yields ranging from moderate to good (Table 1). Also trans-stilbene reacted under the reaction conditions, but