Synthesis of Highly Functionalized Spirocycles and Pentafulvene-Containing Dyes Involving 2-(2'-ketoalkyl)-1,3-indandiones

Synthesis of highly functionalized spiro[4.4]nonane and spiro[4.5]decane motifs by the reaction of dimethylacetylenedicarboxylate (DMAD) with 2-(2'-ketoalkyl)-1,3-indandiones and 2-(3'-ketoalkyl)-1,3-indandiones, respectively, has been developed by utilizing a catalytic amount of DABCO. The tertiary hydroxy-containing spiro[4.4]nonane products were converted into fully conjugated pentafulvene π-systems in an acidic medium through dehydration and unprecedented C-C bond rearrangement.

Controlled Formation of Porous 2D Lattices from C3 -symmetric Ph6 -Me-Tribenzotriquinacene-OAc3

The on-surface self-assembly of molecules to form holey nanographenes is a promising approach to control the properties of the resulting 2D lattice. Usually, planar molecules are utilized to prepare flat, structurally confined molecular layers, with only a few recent examples of warped precursors. However, control of the superstructures is limited thus far. Herein, we report the temperature-controlled self-assembly of a bowl-shaped, acetylated C₃ -symmetric hexaphenyltribenzotriquinacene derivative on Cu(111). Combining scanning tunneling microscopy (STM) and density functional theory (DFT) confirms the formation of highly differing arrangements starting with π-stacked bowl-to-bowl dimers at low coverage at room temperature via chiral honeycomb structures, an intermediate trigonal superstructure, followed by a fully carbon-based, flattened hexagonal superstructure formed by on-surface deacetylation, which is proposed as a precursor for holey graphene networks with unique defect structures.

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, C₃ -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. Congener 12 contains an aromatic 18-π electron system in contrast to the cross-conjugated analog 16. X-ray structure analysis of the precursor dodecaether 15 revealed the formation of a cage-like supramolecular dimer, in which the peripheral dioxane-type ether groups interlace by twelve noncovalent C-H⋅⋅⋅⋅⋅O bonds.

Direct Syntheses of Diphenylmethanol Derivatives from Substituted Benzenes and CHCl3 through Friedel-Crafts Alkylation and Post-Synthetic Hydrolysis or Alcoholysis Catalyzed by Alumina

The present study reports an innovative finding that alumina containing water or primary alcohol catalyzes the hydrolysis or alcoholysis, respectively, of the product formed through AlCl3 -mediated Friedel-Crafts alkylation of methyl-substituted benzenes and CHCl3 . The former and later reactions mainly provided hydroxy- and alkoxy-substituted diarylmethanes, respectively, while the reference reactions without alumina provided bisarylchloromethane. This method enables the selective syntheses of diphenylmethanol derivatives with very simple procedures, without expensive reagents and apparatuses. Furthermore, the alumina used in the reaction could be recycled by washing with water and subsequent drying. From the viewpoint of material recycling, this function is very important for the development of sustainable chemical reactions.

Advances in Diels-Alder/aromatization of biomass furan derivatives towards renewable aromatic hydrocarbons

The effective upgrading of renewable resources into high value-added chemicals is of great significance to achieve the sustainable economic development, as well as the implementation of carbon neutral technologies practically....

Recent Advances on Diels-Alder-Driven Preparation of Bio-Based Aromatics

The preparation of high value-added chemicals from renewable resources is a crucial approach towards a sustainable economy. One prominent alternative to the production of petroleum-based chemicals from fossil resources is through the sequential Diels-Alder/aromatization reactions of biomass-derived furan platforms. This Concept is focused on the recent boom in bio-based furan DA strategies for aromatization of bio-based platform chemicals, particularly that of furfurals, ranging from indirect use and activation strategies to recent examples of direct DA reaction of these electron-withdrawing biomass-derived furans.

Switching the Statistical C3 /C1 Ratio in the Threefold Aromatic Substitution of Tribenzotriquinacenes towards the C3 Isomer

Tribenzotriquinacene (TBTQ) is a bowl-shaped molecule that has been widely used as a molecular building block in supramolecular and materials chemistry. Especially C₃ -symmetric threefold-substituted TBTQs are interesting for these purposes. Until now a general and selective synthetic approach to those C₃ -symmetric products was lacking, mainly because the typically used electrophilic aromatic substitution reactions of the parent TBTQ hydrocarbons produce predominantly the C₁ isomer over the C₃ isomer (3:1 statistical ratio). Herein we introduce a threefold borylation of TBTQ with the C₃ isomer as the main product (2.6:1 C₃ /C₁ ratio). The borylated TBTQ can be converted in good yields into other C₃ -symmetric TBTQs, thus allowing straightforward synthetic access to new building blocks for supramolecular and materials chemistry.

Centrohexaindane: six benzene rings mutually fixed in three dimensions - solid-state structure and six-fold nitration

The solid-state molecular structure of centrohexaindane (), a unique hydrocarbon comprising six benzene rings clamped to each other in three dimensions around a neopentane core, and the molecular packing in crystals of ·CHCl3 are reported. The molecular Td-symmetry and the Cartesian orientation of the six indane wings of in the solid state have been confirmed. The course and limitation of electrophilic aromatic substitution of are demonstrated for the case of nitration. Based on nitration experiments of a lower congener of , tribenzotriquinacene , the six-fold nitrofunctionalisation of has been achieved in excellent yield, giving four constitutional isomers, two nonsymmetrical ( and ) and two C3-symmetrical ones ( and ), all of which contain one single nitro group in each of the six benzene rings. The relative yields of the four isomers (∼3 : 1 : 1 : 3) point to a random electrophilic attack of the electrophiles at the twelve formally equivalent outer positions of the aromatic periphery of , suggesting electronic independence of its six aromatic π-electron systems. In turn, the pronounced conformational rigidity of the centrohexacyclic framework of enables the unequivocal structural identification of the isomeric hexanitrocentrohexaindanes by (1)H NMR spectroscopy.

Dynamic covalent assembly of tribenzotriquinacenes into molecular cubes

Molecular cubes constructed from catechol-functionalized tribenzotriquinacenes and 1,4-phenylene diboronic acids were synthesized in a one-pot procedure by crosslinking 20 individual components through a dynamic covalent approach.

C3-symmetrical tribenzotriquinacene derivatives: optical resolution through cryptophane synthesis and supramolecular self-assembly into nanotubes

Based on a regioselective tris-formylation of a tribenzotriquinacene (TBTQ) hydrocarbon, the racemic C(3)-symmetrical TBTQ-trialdehyde and the corresponding TBTQ-trimethanol were synthesized along with their C(1)-isomers. Conversion of the C(3)-trialdehyde to three diastereomeric TBTQ-based cryptophanes occurring in high yield enabled the preparation of the optically pure C(3)-symmetrical TBTQ-trialdehydes and the determination of their absolute configuration. The racemic C(3)-symmetrical TBTQ-trimethanol was found to form several stable nanotubular aggregates in the solid state.

Merging tribenzotriquinacene with hexa-peri-hexabenzocoronene: a cycloheptatriene unit generated by Scholl reaction

The single-wing extension of the bowl-shaped tribenzotriquinacene (TBTQ) framework with polycondensed aromatic hydrocarbon units has been reported. In the course of a Scholl reaction, one of the three-dimensional bays of the TBTQ core has been bridged by a PAH unit to generate a seven-membered ring within the merged TBTQ-(hexa-peri-hexabenzocoronene) scaffold.