A Molecular Cage Accessed by Threefold Click Reaction of a -Symmetric Triazido-Functionalized Tribenzotriquinacene.

The hitherto unknown hexakis(halomethyl)-functionalized tribenzotriquinacenes (TBTQs) and were synthesized from the key 4b,8b,12b-tribromo-TBTQ derivative by an improved route in 67% overall yield. Extension of the bowl-shaped framework of or by threefold condensation with propargylamine or 2-azidoethylamine afforded the corresponding TBTQ-trialkyne and TBTQ-triazide , respectively. While attempts to construct bis-TBTQ cages, including homodimerization of and heterocoupling of with , were unsuccessful, triazide was found to undergo threefold [3 + 2]-cycloaddition with 3-ethynylaniline and phloroglucinol tripropargyl ether under click chemistry conditions.

π-Extension of the Tribenzotriquinacene Framework: Efficient Vinylene and Arylene Bay Bridging Based on a New C -Symmetric Key Derivative.

1,5,9-Tribromo-2,3,6,7,10,11-hexamethoxy-4b -methyltribenzotriquinacene, a C -symmetric TBTQ derivative, can be prepared conveniently and with high regioselectivity from readily available starting materials. It is a versatile key compound for the synthesis of other chiral 1,5,9-trifunctionalized TBTQ derivatives and π-extended congeners in which the bays of the TBTQ skeleton are bridged by vinylene and 1,2-arylene units. X-ray crystal structure analysis and UV-vis spectroscopy show that vinylene bay-bridging enables better π-conjugation with the arene rings of the TBTQ core than 1,2-arylene bay-bridging does.

Donor-Acceptor Tribenzotriquinacene-Based Molecular Wizard Hats Bearing Three ortho-Benzoquinone Units.

Two π-extended bay-bridged tribenzotriquinacenes ("TBTQ wizard hats") 12 and 16 bearing three mutually conjugated, alternating veratrole-type and ortho-benzoquinone units were synthesized. The electronic properties of these complementarily arranged, nonplanar push-pull systems are affected by the fusion with the rigid, C -symmetric TBTQ core to a different extent, as revealed by X-ray structural analysis, UV-vis spectroscopy and cyclovoltammetry. The combination of three quinone units within the original TBTQ core and three veratrole-type bay bridging units in 12 gives rise to a more efficiently π-conjugated chromophore, as reflected by the shallower shape of wizard hat and its absorption in the visible up to 750 nm in comparison to 16.

Regioconvergent Synthesis of a π-Extended Tribenzotriquinacene-Based Wizard Hat-Shaped Nanographene.

The successful enlargement of the curved π-electron periphery of the wizard hat-shaped polycyclic aromatic compound is described. The target structure features an ,,,,,,,,-nonaphenylene belt fused to a central tribenzotriquinacene unit. The synthesis involves a multiple regioconvergent Scholl-type dehydrocyclization as the key step.

Synthesis of Enantiopure Hydrocarbon Cages Based on an Optically Resolved -Symmetric Triaminotribenzotriquinacene.

The synthesis of the enantiomerically pure, -symmetric covalent hydrocarbon cages (+)-(,)- and (-)-(,)- bearing two -symmetrically functionalized tribenzobenzotriquinacene (TBTQ) vertices is reported. The enantiomerically pure TBTQ building blocks (+)-()- and (-)-()- were prepared via the diastereomeric TBTQ triamides obtained by use of both Boc-d- and Boc-l-phenylglycine as chiral auxiliaries.

Chiral Derivatives of 2-Aminotribenzotriquinacene: Synthesis and Optical Resolution.

Starting from a hitherto unknown 2-aminotribenzotriquinacene, several 2-amino-3-X-substituted TBTQ derivatives, all bearing a single -difunctionalized indane wing, were synthesized as rigid and chiral building blocks for the potential construction of complex supramolecular architectures. Efficient access to two pairs of enantiomeric TBTQ derivatives, namely, the peripheral -nitroaniline (X = NO) and the related anthranilic acid (X = COH), was developed using chiral auxiliaries as the resolving reagents. The structure of the intermediate diastereomers was confirmed by H and C NMR spectroscopy, high-resolution mass spectroscopy (HRMS), and polarimetry.

Scholl-Type Cycloheptatriene Ring Closure of 1,4,9,12-Tetraarylfenestrindanes: Reactivity and Selectivity in the Construction of Fenestrane-Based Polyaromatic Saddles.

The Scholl-type cyclodehydrogenation, generating up to four cycloheptatriene rings around a fenestrindane core, leads to novel, saddle-shaped polyaromatic hydrocarbon derivatives. In this article, we present the results of in-depth experimental and computational work on the oxidative cyclization of various 1,4,9,12-tetraarylfenestrindanes. In particular, the kinetic control of the four-step cyclization of the electronically activated tetrakis(3,4-dimethoxyphenyl) derivative is elucidated.

Organogelating and narcissistic self-sorting behaviour of non-preorganized oligoamides.

Several series of structurally flexible, non-preorganized oligoamides with carboxylic acid, hydride, -propargyl amide and -propyl amide end groups were synthesized and characterized. They were found to be strong organogelators for aromatic solvents. Both the number and density of the amide units, and the nature of the end group were found to influence the gel strength as well as the kinetics of gel formation.

Photochromic, organogelating and self-sorting behaviour of di-(dithienylethene) derivatives.

A series of di-(dithienylethene) (DTE) tetraamides 4 diDTE-X-NHR was synthesized and characterized. Their organogelation property could be rationally optimized by controlling the extent of intramolecular vs. intermolecular hydrogen bonding and also by tuning the extent of side chain interdigitation.

Enantiopure Aromatic Saddles Bearing the Fenestrindane Core.

The synthesis of enantiomerically pure, configurationally stable fenestrindane-based polyaromatic compounds with saddle-like structures is reported. Seven racemic fenestrane synthetic precursors were first screened by chiral HPLC for resolvability into enantiomers. Among the three resolvable precursors, a tribenzofenestrene derivative was resolved on a semipreparative scale, and the absolute configuration of the more slowly eluting enantiomer was established by X-ray crystallography.

Trefoil-Shaped Porous Nanographenes Bearing a Tribenzotriquinacene Core by Three-fold Scholl Macrocyclization.

Porous curved polycyclic aromatic compounds 6 and 14 bearing a tribenzotriquinacene (TBTQ) core encircled by an m,p,p,m,m,p,p,m,m,p,p,m-cyclododecaphenylene belt were synthesized and characterized by NMR spectroscopy and mass spectrometry. These trefoil hydrocarbon macrocycles were constructed in high yield using an intramolecular three-fold Scholl macrocyclization. X-ray crystal analysis of 14 demonstrated a large wizard-hat-shaped structure with three pores (radii 2.

A photo-responsive poly(amide-triazole) physical organogel bearing azobenzene residues in the main chain.

The synthesis of a click poly(amide-triazole) bearing multiple azobenzene units along the main chain was reported. The polymer was found to form strong physical polymer organogels. This structural design facilitates a much more efficient photomechanical effect upon photochemical excitation, and a highly reversible sol-gel transformation can be smoothly triggered by light irradiation and thermal treatment.

Biconcave and Convex-Concave Tribenzotriquinacene Dimers.

A new chiral tribenzotriquinacene bearing an ortho-bromoaniline nucleus was synthesized and optically resolved. The individual enantiomers, the absolute configuration of which was confirmed by single-crystal X-ray structure analysis, were stereoselectively converted into the same pyrazine-fused syn-bis-TBTQ derivative by chirality-assisted Buchwald-Hartwig amination. The corresponding diastereomeric anti-dimer was obtained alongside the syn-dimer from the racemic sample under similar reaction conditions.

Halogen-Bond-Mediated Assembly of a Single-Component Supramolecular Triangle and an Enantiomeric Pair of Double Helices from 2-(Iodoethynyl)pyridine Derivatives.

Construction of single-component supramolecular triangle and unprecedented spontaneous resolution of pairs of intertwined supramolecular 3 - and 3 -double helices by the self-assembly of achiral 2-(iodoethynyl)pyridine and its derivatives have been achieved through intermolecular ethynyl C-I⋅⋅⋅⋅N halogen bonds in the crystalline state. Fine-tuning of the molecular structure of the achiral monomer and choice of solvents for crystallization have a dominant effect on the resultant supramolecular architectures.

From Fenestrindane towards Saddle-Shaped Nanographenes Bearing a Tetracoordinate Carbon Atom.

Two saddle-shaped polycyclic aromatic compounds (8 a and 8 b) bearing an all-cis-[5.5.5.

Identification of influenza polymerase inhibitors targeting polymerase PB2 cap-binding domain through virtual screening.

Influenza A virus is the major cause of epidemics and pandemics worldwide. In this study, virtual screening was used to identify compounds interacting with influenza A polymerase PB2 cap-binding domain (CBD). With a database of 21,351 small molecules, 28 candidate compounds were tested and one compound (225) was identified as hit compound.

Different Gelation and Self-Sorting Properties of Two Isomeric Polyamides Owing to the Parallel versus Anti-Parallel Alignment of Backbone Dipoles.

Two isomeric bottlebrush polyamides P-1 and A-1, with the same repeating monomer dipole units aligned along the polymer backbone in pseudo-parallel and pseudo-antiparallel fashion, respectively, were synthesized and characterized. Both polymers can form thermoreversible gels with aromatic solvents but P-1 was found to show inferior gelation strength compared with that of A-1. Furthermore, despite their close structural resemblance, a 1:1 mixture of the P-1 and A-1 polymers was shown to exhibit self-sorting in the gel state.

Tribenzotriquinacene-Based Crown Ethers: Synthesis and Selective Complexation with Ammonium Salts.

Two tribenzotriquinacene-based crown ethers, TBTQ-dibenzo-24-crown-8 5 and TBTQ-benzo-21-crown-7 6, were prepared from the key TBTQ intermediate, 2,3-dihydroxy-4b,8b,12b,12d-tetramethyltribenzotriquinacene (13), which in turn was synthesized in six steps using two variants of our cyclodehydration method on a multigram scale. The host-guest complexation properties of the TBTQ-based crown ethers 5 and 6 with a paraquat derivative, 16, and two secondary ammonium salts, 17 and 18, were studied by H NMR spectroscopy and mass spectrometry. It was found that host 5 binds to the paraquat derivative 16 as a 1:1 complex in CDCl/CDCN solution with an association constant of K = (9.

Three-Fold Scholl-Type Cycloheptatriene Ring Formation around a Tribenzotriquinacene Core: Toward Warped Graphenes.

A nonplanar polycyclic aromatic compound 6 bearing a tribenzotriquinacene (TBTQ) core merged with an o,p,o,p,o,p-hexaphenylene belt was prepared and characterized by NMR spectroscopy and X-ray crystallography. The key synthesis step involves three Scholl-type cycloheptatriene ring formation steps of the 1,4,8-tris(3',4'-dimethoxyphenyl)-TBTQ derivative 5. The bridging of each of the three TBTQ bays by 1,2-phenylene units in compound 6 gives rise to an unusual wizard hat shaped structure, which represents a promising key intermediate for the construction of nonplanar nanographene molecules bearing a TBTQ core.

o-Quinones Derived from Tribenzotriquinacenes: Functionalization of Inner Bay Positions and Use for Single-Wing Extensions.

Through a surprisingly nonregioselective oxidation process, the reaction of two analogous 2-hydroxy-substituted tribenzotriquinacenes (TBTQs) 8a/8b by o-iodoxybenzoic acid was found to afford the corresponding Cs- and C1-symmetrical TBTQ-o-quinones 6a/6b and 7a/7b, respectively, in 1:1 ratio and excellent combined yields. This finding represents the first example of direct introduction of a functional group into a sterically hindered, inner bay-positions of a parent TBTQ skeleton. In contrast, the analogous reaction with 1-hydroxy-TBTQ 15 failed to produce the desired o-quinone 7a.

Facile Assembly of Chiral Metallosquares by Using Enantiopure Tribenzotriquinacene Corner Motifs.

Invited for the cover of this issue are Wen-Rong Wu, Guang-Jie Xia, and Hak-Fun Chow of The Chinese University of Hong Kong, Xiao-Ping Cao of Lanzhou University and Dietmar Kuck of Bielefeld University. The image depicts how different routes can lead to the same goal. Read the full text of the article at 10.

Facile Assembly of Chiral Metallosquares by Using Enantiopure Tribenzotriquinacene Corner Motifs.

A pair of enantiomerically pure metallosquares based on linear platinum-diacetylene edges and tribenzotriquinacene corner units was synthesized. Their structures were characterized by (1) H-, (13) C- and (31) P NMR spectroscopy as well as MALDI-TOF mass spectrometry and circular dichroism. Based on DFT calculation, the optimized geometry possesses a distorted square conformation in which the four edges are not sitting on the same plane.

Versatile syntheses of hemi-cryptophanes and a metallo-cryptophane from a hexa-functionalized C3v -symmetrical tribenzotriquinacene (TBTQ) derivative.

A number of three-fold C3v -symmetrical tribenzotriquinacene (TBTQ) cavitands were synthesized by a "metamorphosis-to-half" strategy, employing six-fold etherification reactions between the hexakis(chloromethyl)-TBTQ intermediate 2 a and various 5-functionalized resorcinols. X-ray structure analyses of single crystals of the cavitands revealed limited rotational flexibility of the resorcinol bridging units, which enables an apical, nearly co-axial orientation of the three functional groups and, as a consequence, the construction of nanoscale cage-like molecules via covalent or coordination bonding. On this basis, two TBTQ-based hemicryptophanes were prepared from the TBTQ cavitands via covalent bond formation in good yields.