Triple condensation of aryl methyl ketones catalyzed by amine and trifluoroacetic acid: straightforward access to 1,3,5-triarylbenzenes under mild conditions

An overview of the synthetic strategies of C3-symmetric polymeric materials containing benzene and triazine cores and their biomedical applications

C3-symmetric star-shaped materials are an emerging category of porous organic polymers with distinctive properties such as permanent porosity, good thermal and chemical stability, high surface area, and appropriate functionalization that promote outstanding potential in various applications. This review is mostly about constructing benzene or s-triazine rings as the center of C3-symmetric molecules and using side-arm reactions to add functions to these molecules. Over and above this, the performance of various polymerization processes has been additionally investigated in detail, including the trimerization of alkynes or aromatic nitriles, polycondensation of monomers with specific functional groups, and cross-coupling building blocks with benzene or triazine cores. Finally, the most recent progress in biomedical applications for C3-symmetric materials based on benzene or s-triazine have been summarized.

Polymer-Supported-Cobalt-Catalyzed Regioselective Cyclotrimerization of Aryl Alkynes

A convoluted poly(4-vinylpyridine) cobalt(II) (P4VP-CoCl₂) system was developed as a stable and reusable heterogeneous catalyst. The local structure near the Co atom was determined on the basis of experimental data and theoretical calculations. This immobilized cobalt catalyst showed high selectivity and catalytic activity in the [2 + 2 + 2] cyclotrimerization of terminal aryl alkynes. With 0.033 mol % P4VP-CoCl₂, the regioselective formation of 1,3,5-triarylbenzene was realized without 1,2,4-triarylbenzene formation. Further, a multigram-scale (11 g) reaction proceeded efficiently. In addition, the polymer-supported catalyst was successfully recovered and used three times. X-ray photoelectron spectroscopy analysis of the recovered catalyst suggested that cobalt was in the +2 oxidation state. The 1,3,5-triarylbenzene derivatives were applied to the synthesis of a molecular beam electron resist and a polycyclic aromatic hydrocarbon.

Polysubstituted Hexa-cata-hexabenzocoronenes: Syntheses, Characterization, and Their Potential as Semiconducting Materials in Transistor Applications

A series of tetra- and octa-substituted hexa-cata-hexabenzocoronenes (cata-HBCs) were synthesized from tetraryl olefins via iodine- and iron chloride-catalyzed oxidative cyclodehydrogenation reactions. The substitutions on the periphery of the parent HBC serve to modify the photophysical properties, highest occupied molecular orbital-lowest unoccupied molecular orbital gaps, and thermal stabilities of the respective derivatives. The crystal structures were determined to display multiple twists in the framework, resulting in different packing motifs depending on the position, type, and number of functional groups on the hexabenzocoronene framework. Nearly perfect co-facial packing to marginally or extensively shifted co-facial stacks were obtained due to substitution. The single crystals of parent HBC were used to fabricate single-crystal field-effect transistors, from which the highest p-channel mobility of 0.51 cm² V^-1 s^-1 was measured. Thin-film transistors of selected HBCs were also prepared, and 0.61 cm² V^-1 s^-1 was obtained for MeHBC-2. These results attest the potential of these materials as semiconducting materials.

Synthesis and Photophysical Properties of C 3-Symmetric Star-Shaped Molecules Containing Heterocycles Such as Furan, Thiophene, and Oxazole

We report simple strategies to synthesize star-shaped molecules containing different heterocycles integrated with a number of variations. Here, cyclotrimerization, Vilsmeier-Haack reaction, Suzuki-Miyaura cross-coupling, and Van Leusen oxazole synthesis have been used as key steps to introduce diverse five-membered heterocycles such as furan, thiophene, and oxazole. More importantly, readily available starting materials such as thiophene, 2-formyl furan, and 2-acetyl furan were utilized. Also, the fluorescent behavior of these π-conjugated systems was studied. C ₃-Symmetric molecules containing furan moieties show a stronger fluorescence than thiophene-containing star-shaped compounds.

Highly Regioselective Alkylation of Hexabenzocoronenes: Fundamental Insights into the Covalent Chemistry of Graphene

Hexa-peri-hexabenzocoronides (HBC) was successfully used as a model system for investigating the complex mechanism of the reductive functionalization of graphene. The well-defined molecular HBC system enabled deeper insights into the mechanism of the alkylation of reductively activated nanographenes. The separation and complete characterization of alkylation products clearly demonstrate that nanographene functionalization proceeds with exceptionally high regio- and stereoselectivities on the HBC scaffold. Experimental and theoretical studies lead to the conclusion that the intact basal graphene plane is chemically inert and addend binding can only take place at either preexisting defects or close to the periphery.

Environmentally friendly cyclotrimerization of substituted acetophenones catalyzed by a new nanocomposite of γ-Al2O3 nanoparticles decorated with H5PW10V2O40

An efficient protocol for the synthesis of C₃-symmetrical 1,3,5-triarylbenzenes under solvent-free conditions. γ-Al₂O₃/H₅PW₁₀V₂O₄₀ nanocomposite is introduced as a highly reusable catalyst.

A new method for the preparation of 1,3,5-triarylbenzenes catalyzed by nanoclinoptilolite/HDTMA

An efficient method for the preparation of 1,3,5-triarylbenzenes. Natural surface-modified NCP as a new and reusable catalyst. Using solvent-free conditions.

H6P2W18O62/Nanoclinoptilolite as an efficient nanohybrid catalyst in the cyclotrimerization of aryl methyl ketones under solvent-free conditions

A new natural nanohybrid material HPA/NCP was prepared. An efficient and environmentally benign method for cyclotrimerization of acetophenones is reported. Water was the only by-product.

Brønsted acid ionic liquid as a solvent-conserving catalyst for organic reactions

A sulfonyl-containing ammonium-based Brønsted acid ionic liquid was prepared and used as a liquid heterogeneous catalyst for organic reactions. The unique macroscopic phase heterogeneity of the IL in the reaction system not only ensures an excellent catalytic activity of the IL catalyst but also avoids the use of organic reaction solvents. The catalyst system is applicable for a wide range of reactions.