Continuous flow synthesis of azobenzenes via Baeyer–Mills reaction

• Jan H. Griwatz,
• Anne Kunz and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2022, 18, 781–787, doi:10.3762/bjoc.18.78

• and photopharmacology [7], host–guest chemistry [8], molecular mechanics [9][10], to molecular machines [11]. This popularity is due to the ability of ABs to isomerize from their energetically more stable (E)- to the meta-stable (Z)-isomer by irradiation with light [12]. During this isomerization, not

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• Switchable catalysis due to reversible assembly/disassembly Toggling between intra- and intermolecular complexation in nanoswitches Review Catalysis using heteroleptic discrete supramolecular architectures In its early years, supramolecular chemistry mainly focused on host–guest interactions, primarily on

• , organic host molecules such as cyclodextrin [50], pillararenes, and cucurbiturils [51] have been developed in the last decades. Although, these exhibit excellent host–guest encapsulation properties with a variety of organic molecules, there are major drawbacks associated with them: variation of the shape

Synthesis of a new water-soluble hexacarboxylated tribenzotriquinacene derivative and its competitive host–guest interaction for drug delivery

• Man-Ping Li,
• Nan Yang and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2022, 18, 539–548, doi:10.3762/bjoc.18.56

• water-soluble hexacarboxylated tribenzotriquinacene derivative (TBTQ-CB6) was synthesized and used as a supramolecular drug carrier to load the model anticancer drugs dimethyl viologen (MV) and doxorubicin (DOX) via host–guest interactions. The drugs could be effectively released by spermine (SM), a

• molecule overexpressed in cancer cells, through host–guest competitive substitution since TBTQ-CB6 has a stronger binding affinity toward SM than MV and DOX. The host–guest interactions of the complexes of TBTQ-CB6 with MV, DOX and SM were investigated by NMR spectroscopy and fluorescence spectroscopy. The

• novel TBTQ-based host–guest drug delivery system may have potential use in supramolecular chemotherapy. Keywords: competitive substitution; drug delivery; host–guest chemistry; tribenzotriquinacene; water soluble; Introduction Chemotherapy is considered to be one of the most effective strategies in

Tetraphenylethylene-embedded pillar[5]arene-based orthogonal self-assembly for efficient photocatalysis in water

• Zhihang Bai,
• Krishnasamy Velmurugan,
• Xueqi Tian,
• Minzan Zuo,
• Kaiya Wang and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2022, 18, 429–437, doi:10.3762/bjoc.18.45

• supramolecular self-assembled nanosystem based on host–guest interactions between water-soluble tetraphenylethylene-embedded pillar[5]arene (m-TPEWP5) and ammonium benzoyl-ʟ-alaninate (G) in an aqueous medium. The obtained assembly of m-TPEWP5 and G showed aggregation-induced emission (AIE) via the blocking of

• photosynthesis and exhibited a high catalytic efficiency for the photocatalytic dehalogenation reaction of various bromoketone derivatives with good yields in short reaction time in water. Keywords: aggregation-induced emission; Förster resonance energy transfer; host–guest interaction; photocatalysis

• tunable self-assembly, such as vesicles [14][15][16], micelles [17][18][19], nanocrystals [20], coordination-driven assemblies [9][21][22], host–guest interactions [15][23][24][25], etc. In the above systems, catalysts are encapsulated by supramolecular assemblies and thus provide a suitable environment

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• reaction, the anthracene moiety stacks onto the planar triazine of B through π–π stacking and possible charge-transfer interaction between each other, which stabilizes the complex. However, after the reaction, the framework of the product is bent at the 9,10-position, which undermines the host–guest

• alkenyl site, producing the final 1,2-reduction product cis-O-hydroxycinnamyl alcohol 19. As a comparison, in the absence of the β-cyclodextrin host, both the 1,2- and 1,4-reduction products were observed. X-ray crystallography determined the host–guest complex of the coumarin and β-cyclodextrin, which

• cavitand hosts were also modified with imidazolium cationic or carboxylic anionic feet [29]. Before the reaction, NMR analysis of the host–guest complex indicated that the bound guest was in yo-yo motions time-averaged between unsymmetrical J-shaped conformations and symmetrical U-shaped ones. Treatment of

Study on the interactions between melamine-cored Schiff bases with cucurbit[n]urils of different sizes and its application in detecting silver ions

• Jun-Xian Gou,
• Yang Luo,
• Xi-Nan Yang,
• Wei Zhang,
• Ji-Hong Lu,
• Zhu Tao and
• Xin Xiao

Beilstein J. Org. Chem. 2021, 17, 2950–2958, doi:10.3762/bjoc.17.204

• constructed by three different cucurbiturils and synthesized by guest melamine-cored Schiff bases (TBT) through outer-surface interaction and host–guest interactions. TBT forms a TMeQ[6]-TBT complex with TMeQ[6] through outer-surface interaction, while Q[7]-TBT and Q[8]-TBT form complexes with Q[7,8] through

• host–guest interactions. Among them, Q[7]-TBT is selected as a UV detector for the detection of silver ions (Ag+). This work makes full use of the characteristics of each cucurbituril and melamine-cored Schiff base to construct a series of complexes and these are applied to metal detection. Keywords

• , are formed by polymerization of glycoluril, which contains rigid cavities for the study of host–guest chemistry and carbonyl groups for the study of coordination chemistry [16][17][18][19][20]. For the special methyl cucurbit[n]urils with abundant methyl groups, its high density of the

Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions

• Qingkai Zeng,
• Qiumeng Long,
• Jihong Lu,
• Li Wang,
• Yuting You,
• Xiaoting Yuan,
• Qianjun Zhang,
• Qingmei Ge,
• Hang Cong and
• Mao Liu

Beilstein J. Org. Chem. 2021, 17, 2840–2847, doi:10.3762/bjoc.17.195

• association constant up to (2.1 ± 0.3) × 104 M−1. Meanwhile, this macrocycle showed no obvious or only slight enhancement of the fluorescence intensity with selected anions. Keywords: amidobenzene-containing macrocycle; hemicucurbituril; host–guest interaction; macrocycle; modification; Introduction

• domains, such as chemosensors [21], drug delivery [22], and nano materials preparation [23]. Although cucurbiturils with their rigid hydrophobic cavities have found broad application in host–guest chemistry, they suffer from insolubility, difficulty in derivatization, and lack of chromophores

• constants for 1:1 complexation between the host 4 and the guest cations were calculated by Equation 1 [47], where Ka is the association constant of the host–guest interaction, while ΔI is the change in the fluorescence intensity of the host upon gradual addition of the guest, and Δa refers to the different

Host–guest interaction and properties of cucurbit[8]uril with chloramphenicol

• Lin Zhang,
• Jun Zheng,
• Guangyan Luo,
• Xiaoyue Li,
• Yunqian Zhang,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2021, 17, 2832–2839, doi:10.3762/bjoc.17.194

• inhibitory activity of CPE against E. coli. Keywords: antibacterial activity; chloramphenicol; cucurbit[8]uril; host–guest interaction; in vitro cumulative release; stability; Introduction Chloramphenicol (CPE, Figure 1A) is a broad-spectrum antibiotic resulting from the metabolism of chorismic acid in

• and carbon atoms and the cavity has a certain degree of hydrophobicity that can form a stable host–guest inclusion complex with a guest molecule via non-bonding interactions, such as hydrogen bonds, van der Waals forces and ionic dipoles [21][22][23][24][25][26][27][28]. It has been proved that

• sustained-release ability of drug molecules [31][33][34]. However, previous studies rarely reported the interaction between Q[8] and antibiotics, and did not explore the effect of Q[8] on antibacterial activity of antibiotics. Herein, Q[8] was selected as the host and the host–guest interaction between Q[8

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson–Kaas, Van Leusen and Ullmann-type reactions as key tools

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2021, 17, 1374–1384, doi:10.3762/bjoc.17.96

• applicability in the synthesis of dendrimers as well as C3-tripods and also in the host–guest chemistry [17][18][19][20][21]. This architecturally simple yet effective rigid system was first prepared in 1894 by Kipping [22] involving the trimerization of 3‐phenylpropionic acid under acidic conditions but

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

• Cansu Esen and
• Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

• ). Since then, many synthetic routes have been developed in order to synthesize artificial matter that mimics the performance of natural tissues. Therefore, many reinforcement methods have been suggested, i.e., host–guest interactions [4][5], double network formation [6][7][8], and reinforcer addition [9

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• also discussed. Keywords: host–guest chemistry; macrocycles; noncovalent interactions; supramolecular photocatalysis; Introduction Enzyme-catalyzed reactions are often carried out fantastically in nature via noncovalent interactions of a substrate [1][2]. Inspired by these natural processes, chemists

• have begun to develop artificial supramolecular systems that provide a similar environment to perform various catalytic reactions where substrates are captured via host–guest interactions [3]. In addition, these systems aim to control the product selectivity and the rate of catalytic reactions by

• materials that have been exploited for photocatalytic applications, including photocatalytic dye degradations and hydrogen evolution. To successfully perform supramolecular photocatalytic reactions, various photophysical and photochemical properties of the host–guest system need to be considered [4]: i) the

Construction of pillar[4]arene[1]quinone–1,10-dibromodecane pseudorotaxanes in solution and in the solid state

• Xinru Sheng,
• Errui Li and
• Feihe Huang

Beilstein J. Org. Chem. 2020, 16, 2954–2959, doi:10.3762/bjoc.16.245

• 450001, P. R. China 10.3762/bjoc.16.245 Abstract We report novel pseudorotaxanes based on the complexation between pillar[4]arene[1]quinone and 1,10-dibromodecane. The complexation is found to have a 1:1 host–guest complexation stoichiometry in chloroform but a 2:1 host–guest complexation stoichiometry

• the further capping of the pseudorotaxanes to construct rotaxanes. Keywords: host–guest chemistry; pillar[4]arene[1]quinones; pillararenes; pseudorotaxanes; supramolecular chemistry; Introduction Relying on the research of basic science, supramolecular chemistry has become an important mean for

• reports [44][45]. We found that H and G can be used to build a [3]pseudorotaxane in the solid state but a [2]pseudorotaxane in solution. Results and Discussion Host–guest complexation in the solid state Cocrystals of H and G were obtained by slow evaporation of the solution in methanol. The X-ray

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• ), cucurbit[7]uril (3), and the two chalcones 1 and 2 in aqueous solution [48]. When the hosts 3 and 4 were mixed with the trans-chalcones 1 and 2 as guests in a 1:1:1:1 ratio, instantly a statistical mixture formed displaying all four possible host–guest complexes. After the exposure to an acid, the ensuing

• specific release of the guest (PF6−) with the consequent disassembly of the cage [Zn4(65')4]8+ (SelfSORT-II). In SelfSORT-II, the host–guest complex [Zn4(64')4]8+•(C6H12) remained intact, while ≈17% decrease in [Zn4(66')4]8+•(NO3−) was observed. The addition of another aliquot of 4-methoxyaniline to

• SelfSORT-II disassembled the host–guest complex [Zn4(64')4]8+•(C6H12) with the concomitant release of the encapsulated cyclohexane thus generating the state SelfSORT-III. In this process, the 1H NMR signals corresponding to [Zn4(66')4]8+•(NO3−) remained unchanged. At last, heating the mixture to 70 °C for

A heterobimetallic tetrahedron from a linear platinum(II)-bis(acetylide) metalloligand

• Matthias Hardy,
• Marianne Engeser and
• Arne Lützen

Beilstein J. Org. Chem. 2020, 16, 2701–2708, doi:10.3762/bjoc.16.220

• obtain analogues cages in future work to explore the properties of these system in terms of their host–guest chemistry or their magnetic behavior. Experimental General All reagents and solvents were purchased from commercial sources and used as received without any further purification. NMR spectra were

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• hydrophobic effect and to host–guest π–π interactions. Hydrophobic surface simulations showed that TBTQ-(OG)6 and C60 forms an amphiphilic supramolecular host–guest complex, which further assembles to microspheres with diameters of 0.3–3.5 μm, as determined by scanning electron microscopy. Keywords

• : fullerenes; host–guest systems; microspheres; supramolecular chemistry; tribenzotriquinacene; Introduction In the field of supramolecular chemistry, host–guest association through noncovalent interactions is an interesting and exciting topic, especially for the encapsulation of various fullerenes, such as

• attention for potential applications in host–guest recognition, such as gas storage and cationic complexation [31][32][33]. In the past years, the recognition of the biological and pharmaceutical relevance of fullerenes, such as their photodynamic activity, phototoxicity, HIV-1 protease inhibitor ability

Host–guest interaction of cucurbit[8]uril with oroxin A and its effect on the properties of oroxin A

• Zhishu Zeng,
• Jun Xie,
• Guangyan Luo,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2020, 16, 2332–2337, doi:10.3762/bjoc.16.194

• the inclusion compound with Q[8]. Keywords: cucurbit[8]uril; host–guest interaction; inclusion complex; oroxin A; properties; Introduction Cucurbit[n]urils (Q[n]s) are a family of macrocyclic cage compounds synthesized by the condensation of glycoluril and formaldehyde in a strong acidic solution [1

• ][2][3]. As a consequence of the specific structural features of Q[n]s, which have two hydrophilic “portals” decorated with partially negatively charged carbonyl groups and a hydrophobic cavity [4], cucurbit[n]urils are able to form host–guest complexes with a range of drugs [5][6][7]. These complexes

• constants [14] have shown that Q[n]s are ideal drug carriers [15][16]. Moreover, Q[n]s can enhance the physical stability [17][18] and increase the solubility [19][20] of drug molecules. After Q[n]s forms a host–guest complex with drug molecules, it can also improve the bioavailability and delivery capacity

Design and synthesis of a bis-macrocyclic host and guests as building blocks for small molecular knots

• Elizabeth A. Margolis,
• Rebecca J. Keyes,
• Stephen D. Lockey IV and
• Edward E. Fenlon

Beilstein J. Org. Chem. 2020, 16, 2314–2321, doi:10.3762/bjoc.16.192

• . Keywords: alkynes; azides; host–guest; macrocycles; molecular knots; Introduction Macrocycles have played a central role in the development of molecular recognition, self-assembled molecular devices, and molecular topology [1][2][3][4][5][6]. For example, early work by Pedersen on crown ethers [1], Lehn

• 0.02 to 0.09 ppm for some aromatic resonances on the host. These shifts suggest at least some host–guest complex was formed, even in this competitive polar solvent mixture. The full TLC sequence was tested by reacting 1 and 2 (1:1 ratio) in a solvent mixture of acetonitrile/dichloromethane/methanol (1

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• non-radiative transitions can be achieved by the host–guest method [50][51][52] or by crystallization [53][54][55][56][57]. In difference to the liquid phase, the highly ordered packing and the restriction of molecular motions in the crystalline state favor a persistent luminescence. The promotion of

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• stereoselective approaches of substrates and reagents or catalysts in a variety of processes. Examples include the substrate–enzyme recognition (the host–guest interaction) responsible for inducing pharmacological activity, the DNA-intercalation capable of generating biomolecular activity, molecular dynamics [63

Aryl-substituted acridanes as hosts for TADF-based OLEDs

• Naveen Masimukku,
• Dalius Gudeika,
• Oleksandr Bezvikonnyi,
• Ihor Syvorotka,
• Rasa Keruckiene,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 989–1000, doi:10.3762/bjoc.16.88

• , high singlet and triplet energies (higher than those of the guest) are required for host compounds for qualifying host–guest energy transfer, thus implying restrict of the emissive excitons on the TADF emitters [11]. High glass-transition temperatures are also required for increasing the morphological

The interaction between cucurbit[8]uril and baicalein and the effect on baicalein properties

• Xiaodong Zhang,
• Jun Xie,
• Zhiling Xu,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2020, 16, 71–77, doi:10.3762/bjoc.16.9

• Xiaodong Zhang Jun Xie Zhiling Xu Zhu Tao Qianjun Zhang Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province, Guizhou University, Guiyang 550025, China 10.3762/bjoc.16.9 Abstract The host–guest interactions between baicalein (BALE) and cucurbit[8]uril (Q[8]) and the

• corresponding properties of the inclusion complex were studied using 1H NMR, IR and UV–vis spectroscopy and DTA. The results showed that BALE forms an inclusion compound (1:1) with Q[8], and the properties of baicalein are changed by cucurbit[8]uril. Keywords: baicalein; cucurbit[8]uril; host–guest interaction

• compounds such as calixarenes, crown ethers and cyclodextrins, which can be used to form a stable inclusion complex with the drug, and improving the bioavailability of the drug [34][35]. Herein, we describe the results of the investigations of host–guest interactions between BALE and Q[8] in an aqueous

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• , as elucidated by the crystallographic structure of a 1:1 host–guest BAPTA system [2]. This moiety has been exploited in the development of various fluorescent supramolecular chemosensor systems and even molecular logic systems [3][4][5][6][7][8][9][10][11]. Equally, the incorporation of

A chiral self-sorting photoresponsive coordination cage based on overcrowded alkenes

• Constantin Stuckhardt,
• Diederik Roke,
• Wojciech Danowski,
• Edwin Otten,
• Sander J. Wezenberg and
• Ben L. Feringa

Beilstein J. Org. Chem. 2019, 15, 2767–2773, doi:10.3762/bjoc.15.268

• between the three isomers. Two of the isomers were able to form host–guest complexes opening up new prospects toward stimuli-controlled substrate binding and release. Keywords: coordination cages; molecular motors; molecular switches; overcrowded alkene; palladium; Introduction Supramolecular

• metal centers has been used to control host–guest interactions [25][26][27][28], structural composition [29], and sol–gel transition [30]. However, dithienylethene undergoes a limited structural change upon photoisomerization and, up to now, photoswitchable ligands based on other types of photochromic

• formed revealing that a chiral self-sorting process takes place. In addition, two of the cage isomers can bind a tosylate anion in solution by formation of a host–guest complex. Results and Discussion Ligands Z-1 and E-1 (Scheme 1) were synthesized by a Suzuki cross-coupling reaction of 3

Anion-driven encapsulation of cationic guests inside pyridine[4]arene dimers

• Anniina Kiesilä,
• Jani O. Moilanen,
• Anneli Kruve,
• Christoph A. Schalley,
• Perdita Barran and
• Elina Kalenius

Beilstein J. Org. Chem. 2019, 15, 2486–2492, doi:10.3762/bjoc.15.241

• and studied by multiple gas-phase techniques, ESI-QTOF-MS, IRMPD, and DT-IMMS experiments, as well as DFT calculations. The comparison of classical resorcinarenes with pyridinearenes by MS and NMR experiments reveals clear differences in their host–guest chemistry and implies that cation encapsulation

• synthesis of pyridine[4]arenes dates back to 2001 [4], their host–guest chemistry is still under-explored. Both macrocycles are concave and are known to form capsular assemblies via intermolecular hydrogen bonding [5][6]. Pyridine is significantly less electron-rich than benzene. Consequently, pyridinearene

• dimeric resorcin[4]arene and pyridine[4]arene capsules, we highlight here unique host–guest properties of pyridinearene capsules. In marked contrast to the corresponding resorcin[4]arene capsules, cation binding is clearly feasible, when anions bind in an exo-site and support cation encapsulation by