Efficient catenane synthesis by cucurbit[6]uril-mediated azide–alkyne cycloaddition

• Antony Wing Hung Ng,
• Chi-Chung Yee,
• Kai Wang and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2018, 14, 1846–1853, doi:10.3762/bjoc.14.158

• –ligand coordination, charge transfer, π-stacking and hydrophobic interactions, for the later interlocking of additional macrocycles to give higher-order [n]catenanes. The new building blocks were synthesized following similar procedures as previously described [24]. Catenane synthesis by CBAAC Synthesis

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

• Cristina Morar,
• Pedro Lameiras,
• Attila Bende,
• Gabriel Katona,
• Emese Gál and
• Mircea Darabantu

Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145

• previously reported nanosystems as polymeric nanoparticles. In covalent series, G-1 dendron D-N

  NH itself (as unexpected reference) self-assembled into nanospheres with a high D value (694 nm). We ascribed this packing ability to three basic π stacking interactions [72] associating stratified parallel

• , 8 and 9; the red arrow indicates the nano-particles that aggregate. D is the average diameter of nanospheres. Proposed π-stacking interactions in compounds D-N

  NH and 5–7a. Convergent versus divergent three steps (a–c) synthesis of central building blocks C1 and C3. Synthesis of G-1 dendrons D-Cl

Steric “attraction”: not by dispersion alone

• Ganna Gryn’ova and
• Clémence Corminboeuf

Beilstein J. Org. Chem. 2018, 14, 1482–1490, doi:10.3762/bjoc.14.125

• cages [10]. Intermolecular interactions in hydrocarbons are also subject to significant dispersion contribution. In the unsaturated systems, from benzene dimer to higher acenes and, ultimately, graphenes, dispersion is increasingly the key force behind the π–π stacking interactions [11]. Large and flat

• electrostatic contribution to it [25]. For example, “dispersion dominates and electrostatics commands” is the ‘punch line’ of the 2017 computational study on the σ–σ, σ–π and π–π stacking interactions between benzene, cyclohexane and some of their fluorinated derivatives [26]. The authors show that while

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• including formation of metallophilic d8···d8 interactions and/or π–π stacking of the coordinating ligands [67][92] as well as excited-state interactions such as formation of excimers [93][94]. Although they may be usefully employed to shift both absorption and emission spectra

Enantioselective phase-transfer catalyzed alkylation of 1-methyl-7-methoxy-2-tetralone: an effective route to dezocine

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 1421–1427, doi:10.3762/bjoc.14.119

• , then two additional interaction forces in the complex are produced on the same plane, including: 1) the carbonyl of 2 makes a hydrogen bond with the hydroxy group of C7; 2) the phenyl group of 2 forms a face-to-face π-stacking interaction with the benzyl moiety of C7. The complex of 2 with C7 goes to

Are dispersion corrections accurate outside equilibrium? A case study on benzene

• Tim Gould,
• Erin R. Johnson and
• Sherif Abdulkader Tawfik

Beilstein J. Org. Chem. 2018, 14, 1181–1191, doi:10.3762/bjoc.14.99

• been increasing interest in utilizing non-covalent π-stacking for synthetic catalysis – and it is notable that most structures shown in a recent review on the topic feature rings that interact at distances greater than the potential minimum [26]. Benzene dimers also feature in the S22 benchmark set [21

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

• heterocyclic rings such as furan 62 and 63 [126], thiophene 64 [127] and pyridine 65 (Figure 11) [128]. These conjugates exhibit potent antibacterial and antiprotozoal activity with much reduced toxicity. It was further concluded that π-stacking, H-bonding with the floor of the minor groove along with

An uracil-linked hydroxyflavone probe for the recognition of ATP

• Márton Bojtár,
• Péter Zoltán Janzsó-Berend,
• Dávid Mester,
• Dóra Hessz,
• Mihály Kállay,
• Miklós Kubinyi and
• István Bitter

Beilstein J. Org. Chem. 2018, 14, 747–755, doi:10.3762/bjoc.14.63

• recognition sites [16][18][19][33], or Zn-dipicolylamine complexes [21][23][24] attracting the negatively charged phosphate units of ATP and by π-stacking between the fluorophores of the sensors and the adenine moiety of ATP [29]. In aqueous solutions at physiological pH, the tetra-charged anionic ATP

• , 4’-dimethylaminohydroxyflavone) was utilized by Pivovarenko and co-workers in ATP sensing in aqueous solution and in mitochondria [34][44]. DMHF was found to form 1:1 and 1:2 complexes with ATP. The two components were held together by π-stacking and by electrostatic interactions of the positively

• [45], however, none of them are the result of rational design. Base pairing is a well-known phenomenon in the double helix structure of DNA since the work of Watson and Crick. It is also known that the cohesion of the double strand is provided by the efficient π-stacking interaction [46]. Adding

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• luminance of 100 cd/m2, slightly red-shifted compared to the emission observed for doped OLEDs. Clearly, the specific design of D6 and its highly twisted structure efficiently weakened the π–π-stacking interactions, providing a general design rule for the elaboration of TADF emitters insensitive to the

Fluorogenic PNA probes

• Tirayut Vilaivan

Beilstein J. Org. Chem. 2018, 14, 253–281, doi:10.3762/bjoc.14.17

• of the TO label to DNA or RNA duplexes were occasionally observed, this could be suppressed by using a shorter linker (as in FIT PNA probes, vide infra) or by combination with a second dye, such as pyrene, that can interact with TO by π-stacking. Such a combination in a short PNA probe has been used

Synthesis and supramolecular properties of regioisomers of mononaphthylallyl derivatives of γ-cyclodextrin

• Markéta Bláhová,
• Sergey K. Filippov,
• Lubomír Kováčik,
• Jiří Horský,
• Simona Hybelbauerová,
• Zdenka Syrová,
• Tomáš Křížek and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2017, 13, 2509–2520, doi:10.3762/bjoc.13.248

• the shape of peaks, but also in the value of the chemical shifts. For both regioisomers the concentration dependence of chemical shifts in aromatic and allyl areas indicates intermolecular association such as inclusion of the naphthylallyl moiety into the cavity of γ-CD or π stacking of naphthyls. The

One-pot syntheses of blue-luminescent 4-aryl-1H-benzo[f]isoindole-1,3(2H)-diones by T3P^® activation of 3-arylpropiolic acids

• Melanie Denißen,
• Alexander Kraus,
• Guido J. Reiss and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2017, 13, 2340–2351, doi:10.3762/bjoc.13.231

• 5 (left) and a centrosymmetric dimer formation by π–π interactions (right) (ellipsoids are drawn at the 40% probability level). The ORTEP-type plot of the asymmetric unit of the crystal structure 6 (top) and π-stacking interactions (bottom) (ellipsoids are drawn at the 40% probability level

Complexation of molecular clips containing fragments of diphenylglycoluril and benzocrown ethers with paraquat and its derivatives

• Leonid S. Kikot',
• Catherine Yu. Kulygina,
• Alexander Yu. Lyapunov,
• Svetlana V. Shishkina,
• Roman I. Zubatyuk,
• Tatiana Yu. Bogaschenko and
• Tatiana I. Kirichenko

Beilstein J. Org. Chem. 2017, 13, 2056–2067, doi:10.3762/bjoc.13.203

• π–π stacking and C–H∙∙∙X (X = N, O, F ...) interactions. The stability of inclusion complexes based on molecular clips and paraquat derivatives depends on two factors: 1) the value of the positive charge on the dipyridinium fragment of paraquat derivatives, the distribution of which is well

• paraquat, the following moieties may be involved: the glycoluril fragment (hydrogen bonds involving the oxygen atoms of the carbonyl groups), the catechol part of the crown ether fragments (π–π stacking interactions) and the polyether chains of benzocrown ethers (C–H···О interactions). The first two

• complexation constant of the clip 6 with paraquat (7), which was: lgK = 1.46 ± 0.01 (−ΔG = 1.96 ± 0.02 kcal/mol). The complex of clip 6 with paraquat (7) may be stabilized through π–π stacking interactions of the electron-deficient aromatic rings of paraquat and the electron donating veratrol fragments of the

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

• solvent-free mechanomilling [50]. By varying the electron density on the aromatic aldehydes, it was observed that electron deficient aldehydes provided a better yield with excellent stereo selectivity over electron rich systems. The observed result suggests that a π–π stacking interaction between electron

Sugar-based micro/mesoporous hypercross-linked polymers with in situ embedded silver nanoparticles for catalytic reduction

• Qing Yin,
• Qi Chen,
• Li-Can Lu and
• Bao-Hang Han

Beilstein J. Org. Chem. 2017, 13, 1212–1221, doi:10.3762/bjoc.13.120

• described as the Langmuir–Freundlich isotherm [47]. The polymer matrix has higher adsorption capacity for 4-NP due to π–π stacking interactions, which can encourage 4-NP molecules to enter the polymer channel to form the adsorbed species [54]. At the same time, the hydrogen atom is introduced onto the

An eco-compatible strategy for the diversity-oriented synthesis of macrocycles exploiting carbohydrate-derived building blocks

• Sushil K. Maurya and
• Rohit Rana

Beilstein J. Org. Chem. 2017, 13, 1106–1118, doi:10.3762/bjoc.13.110

• inherent properties including stability towards acid–base hydrolysis, active participation in H-bonding, dipole–dipole and π-stacking interactions [37][64][65][66]. The reaction would then afford a range of acyclic precursors, which could then undergo the intramolecular cyclization reaction to furnish the

Correlation of surface pressure and hue of planarizable push–pull chromophores at the air/water interface

• Frederik Neuhaus,
• Fabio Zobi,
• Gerald Brezesinski,
• Marta Dal Molin,
• Stefan Matile and
• Andreas Zumbuehl

Beilstein J. Org. Chem. 2017, 13, 1099–1105, doi:10.3762/bjoc.13.109

• change is significant and represents the expected red shift. Although contributions from changes in π–π stacking on spectroscopic properties cannot be excluded, the observed red shift in compressed flipper monolayers is consistent with the earlier experiments on the planarization of monomeric flipper

Substitution of fluorine in M[C₆F₅BF₃] with organolithium compounds: distinctions between O- and N-nucleophiles

• Anton Yu. Shabalin,
• Nicolay Yu. Adonin and
• Vadim V. Bardin

Beilstein J. Org. Chem. 2017, 13, 703–713, doi:10.3762/bjoc.13.69

• (Scheme 9) due to the π-stacking interactions between C6H5 and C6F5 moieties (Scheme 10), which is excluded in cases of nucleophilic alkylation. While reactions of K[C6F5BF3] with C-nucleophiles give the significant amount of K[2-NuC6F4BF3] the related isomers are not formed under the action of O

• ). During nucleophilic phenylation the π–stacking interaction between C6H5 and C6F5 moieties can be responsible for increased yield of M[2-PhC6F4BF3]. 4. The formation of M[2-RC6F4BF3] proceeds through the coordination of RLi (polarized C–Li bond) to a fluorine atom of the BF3 moiety and subsequent

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• interaction between the positively charged amino group in DOX and the negatively charged groups on the CD surface can take place. Also van der Waals and π–π stacking interactions were attributed as contributing factors to the DOX loading and DOX incorporation into the hollow CD cavity. Drug release at acidic

A new class of organogelators based on triphenylmethyl derivatives of primary alcohols: hydrophobic interactions alone can mediate gelation

• Wangkhem P. Singh and
• Rajkumar S. Singh

Beilstein J. Org. Chem. 2017, 13, 138–149, doi:10.3762/bjoc.13.17

• ][21][22]. As mentioned above, developing a new gelator is still largely a trial and error method. The most widely used design strategy involves the inclusion of structural components favouring intermolecular non-covalent interactions (like H-bonding, π-stacking, donor–acceptor interaction, metal

• ][24]. Similar is the case for π-stacking interaction (seen in naphthalene, anthracene, pyrene, perylene, etc.) which has been mostly used in combination with other types of secondary interactions in the discovery of many gelators [25][26]. This holds true for many other non-covalent interactions as

• geometry (unlike the planar geometry of say anthracene, pyrene, etc.), π–π stacking will be favoured only between benzene units of different trityl groups. A small library of triphenylmethyl derivatives was synthesized from the corresponding primary alcohols employing a single step reaction and detailed

Supramolecular frameworks based on [60]fullerene hexakisadducts

• Andreas Kraft,
• Johannes Stangl,
• Ana-Maria Krause,
• Klaus Müller-Buschbaum and
• Florian Beuerle

Beilstein J. Org. Chem. 2017, 13, 1–9, doi:10.3762/bjoc.13.1

• ][34][35][36][37][38][39][40][41][42][43][44][45] or π–π-stacking [46] that retain porosity in the solid state under activation conditions have been reported so far. One possible way to enhance stability and shape-persistency might be the implementation of polyfunctional building blocks in order to

Synthesis of spiro[isoindole-1,5’-isoxazolidin]-3(2H)-ones as potential inhibitors of the MDM2-p53 interaction

• Salvatore V. Giofrè,
• Santa Cirmi,
• Raffaella Mancuso,
• Francesco Nicolò,
• Giuseppe Lanza,
• Laura Legnani,
• Agata Campisi,
• Maria A. Chiacchio,
• Michele Navarra,
• Bartolo Gabriele and
• Roberto Romeo

Beilstein J. Org. Chem. 2016, 12, 2793–2807, doi:10.3762/bjoc.12.278

• 180° rotation of the isoindolinone core such that the benzyl group and dialkylamide occupy the Leu26 and Phe19 pockets, respectively. The reoriented binding mode, similar to the MI63 analogue, takes advantage of the π–π stacking interaction with His96 of MDM2 and the benzyl moiety of compound 6e, and

Effects of solvent additive on “s-shaped” curves in solution-processed small molecule solar cells

• John A. Love,
• Shu-Hua Chou,
• Ye Huang,
• Guilllermo C. Bazan and
• Thuc-Quyen Nguyen

Beilstein J. Org. Chem. 2016, 12, 2543–2555, doi:10.3762/bjoc.12.249

• reflection, suggesting a quite well-ordered film. Additionally, there is a small peak at 1.79 Å−1, corresponding to a spacing of 3.5 Å, which we attribute to π–π stacking. There is a broad feature centered at Q = 1.5 Å−1 which is seen in both films and at all orientations, which is the convolution of two

• with DIO, the alkyl stacking peak is again though is less prominent in-plane, while the π-stacking peak is more prominent. Assuming the alkyl and π-stacking directions are perpendicular, this suggests the material primarily adopts an edge-on orientation. This is in contrast with the preferential “face

A self-assembled cyclodextrin nanocarrier for photoreactive squaraine

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248

• inclusion between the adamantane groups and the cyclodextrin cavities at the surface of cyclodextrin vesicles (CDVs) results in efficient immobilization of the squaraine on a nanocarrier. In addition, π–π stacking (and hence inactivation) of the squaraine is supressed due to the steric separation of the

• . In a first set of experiments, we investigated the photochemical properties of AdSq in acetonitrile (Figure 2). The absorption spectrum shows a peak at 665 nm indicative of the presence of squaraine monomers in the solution. A shoulder around 610 nm indicates aggregation of the squaraine due to π–π

• stacking. A comparison of absorption spectra in different solvents revealed that the amount of aggregation is rather low in acetonitrile or ethanol but increases dramatically if water is used as a solvent (see Figure S1 in Supporting Information File 1). This is in agreement with literature and highlights

Sydnone C-4 heteroarylation with an indolizine ring via Chichibabin indolizine synthesis

• Florin Albota,
• Mino R. Caira,
• Constantin Draghici,
• Florea Dumitrascu and
• Denisa E. Dumitrescu

Beilstein J. Org. Chem. 2016, 12, 2503–2510, doi:10.3762/bjoc.12.245

• of 12c include two additional intermolecular C–H···O bonds and an offset π-stacking interaction between the indolizine ring and its inversion-related counterpart, with the shortest centroid···centroid distance 3.718(1) Å. The 1H NMR spectra of compounds 12 confirmed the indolizine structure of the