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

• backbone functionalized phenanthrenes and helicenes of various sizes in good yields. Keywords: continuous-flow reactor; flow chemistry; helicenes; light-driven cyclization reaction; photocyclization; stilbenes; Introduction Phenanthrenes are versatile intermediates toward polycyclic aromatic hydrocarbons

• derivatives. We choose stilbenes with bromide and methyl substituents, as the latter can be used in subsequent oxidation, deprotonation, and radical addition reactions, whereas the former opens access to various functional groups via lithium-halogen exchange or cross-coupling chemistry. Methoxy groups were

• also tolerated, but nitro- and amino groups containing stilbenes showed low conversion or decomposition. Meta-substituted substrates gave inseparable regioisomers, and ortho-substitution led to low conversion. In the case of substrate 1e, a separable 1:1 mixture of regioisomers 2e and 2e’ was obtained

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

• affinity [21]. Analysis of stilbenes 44a–f shows that a monomethylated or dimethylated amine at one end of the stilbene core leads to strong binding affinity for Aβ1-40 aggregates, while a free amine or nitro group reduces affinity. The opposite end of the stilbene core can be substituted with a hydroxy or

• analogue takes place inside an HPLC sample loop [43]. Diphenyl-1,2,4- and diphenyl-1,3,4-oxadiazoles The replacement of the stilbene ethylene linker with different heterocycles is a common strategy in medicinal chemistry used to improve the pharmacokinetics and/or pharmacodynamics of stilbenes (Scheme 5A

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

• Raney nickel did not provide full conversion to the respective anilines. Furthermore, the reaction mixtures contained products 7 and 8. At higher pressure (20 atm), complete nitro group and C=C reduction of stilbenes 5 and 6 to compounds 7 and 8, respectively, took place (Table 4). Several other

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• devices. Many different organic photochromic molecules are known in photochemistry, such as azobenzenes, stilbenes, spiropyranes, fulgides, diarylethenes and chromenes among many others (Figure 1) [16]. The photochromic processes that take place when such compounds are illuminated can be divided in three

• to the initial isomer even at elevated temperatures (e.g., fulgides and diarylethenes). ● T-type (thermally reversible type); the photogenerated isomer thermally reverts to the initial form (e.g., azobenzenes, stilbenes or spiropyranes). One of the most used organic chromophores for optical switching

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

• substrate range with regard to the carboxylate substrate and found that the new protocol is particularly suitable for 2-nitro-substituted carboxylates (Table 3). Various compounds of this type were converted to stilbenes in good yields. In contrast, arenecarboxylates with a nitro-group in meta- or para

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

• little else is known about the photophysics of guests in this capsule. This research was undertaken to understand what controls the behavior of stilbenes in this and related constrained environments. Results and Discussion The space inside capsule 1.1 is defined by two pyramids comprising resorcinarenes

• depicted in Figure 1A, the square prisms are twisted by about 45° along their long axes. A typical aromatic guest such as benzene fits best when it is nestled diagonally in a prism’s space. Accordingly, the aromatic rings of longer molecules such as biphenyls and stilbenes cannot be coplanar in their

• a fully reversible process with long chain alkane guests. We are currently pursuing this application with stilbenes and studying the exchange of subunits in the process [12][13]. Many fluorescent sensors have been reported in the literature [14][15][16][17], however they usually respond to chemical

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

• -dibromostilbene (12) was produced. Bromination of cis-stilbene under solvent-free PV-PTFE conditions gave an almost pure D,L-dibromostilbene (10), which was accompanied by small amounts of cis- and trans-stilbenes (Table 1, entry 5). trans-stilbene (11) could not be brominated under PV-PTFE conditions in solution

• reaction apparatus, b) reaction mixture (note a thin stream of bromine vapors flowing straight down), c) bromination was completed when the color of bromine vapors persisted, d) after a work-up tube was inserted bromine vapors were consumed. Bromination of stilbenes. Addition reactions of bromine under

An expedient synthesis of 5-n-alkylresorcinols and novel 5-n-alkylresorcinol haptens

• Kirsti Parikka and
• Kristiina Wähälä

Beilstein J. Org. Chem. 2009, 5, No. 22, doi:10.3762/bjoc.5.22

• preparation of stilbenes from benzyltriphenylphosphonium salts and aryl aldehydes [30][31] and also include reactions of stabilized ylids with aryl aldehydes or short alkyl chain alkanals [32][33][34][35][36] and the preparation of o- and p-nitrostyrenes from the highly reactive formaldehyde [37]. To provide

Convenient methods for preparing π-conjugated linkers as building blocks for modular chemistry

• Jiří Kulhánek,
• Filip Bureš and
• Miroslav Ludwig

Beilstein J. Org. Chem. 2009, 5, No. 11, doi:10.3762/bjoc.5.11

• and 4-bromobenzyl(triphenyl)phosphonium bromide [37] by the Wittig reaction [37][38] in 37 and 54% yields, respectively. In contrast to the Horner–Wadsworth–Emmons reaction, this procedure afforded both (E)- and (Z)-stilbenes that were isomerized by heating with traces of iodine in toluene to afford

• pure (E)-stilbenes [38]. However, compared to N,N-dimethylaminostilbene, the isomerization of 4-bromo-4′-methoxystilbene required twelve times the prolonged reaction time (4 vs. 48 h) while the isomerisation of unsubstituted 4-bromostilbene did not take a place at all. Hence, 5a had to be prepared by

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

• . Conclusion In this paper we have described the synthesis and comparative structures of a series of diastereoisomers of vicinal difluoro compounds, which were generated by converting stilbenes to 1,2-difluoro,1-2-diphenylethanes 13 and then oxidation of the aryl rings to generate 2,3-difluorosuccinic acids