DBSA catalyzed cyclotrimerization of acetophenones: An efficient synthesis of 1,3,5-triarylbenzenes under solvent-free conditions

DBU-Mediated Isomerization/6-π Electro-Cyclization/Oxidation Cascade of Sulfonyl-Substituted Allenyl Ketones for the Construction of Hetero-1,3,5-Trisubstituted Benzene

1,3,5-tri-substituted benzene rings emerged with unique properties has widespread applications in materials, boosting the rapid development of their synthesis. Despite the significance, the direct construction of hetero-1,3,5-trisubstituted benzene core was far less-developed. Herein, we realized a DBU-mediated isomerization/6-π electro-cyclization/oxidative aromatization cascade of sulfonyl-substituted allenyl ketones under an air atmosphere (DBU=1,8-diazabicyclo[5.4.0]undec-7-ene). This versatile protocol featured metal-free conditions, easy operation, and broad functional group tolerance provides a new avenue for the construction of hetero-1,3,5-tri-substituted benzene.

Decomposition of Unpolarized Fluorescence Spectrum of Uniaxially Oriented 1,3,5-Triphenylbenzene Microcrystals Into Polarized Fluorescence Spectra

Luminescence from solids such as crystals and aggregates is of growing academic and industrial interest. In this study, we report decomposition of the unpolarized fluorescence spectrum of uniaxially oriented 1,3,5-triphenylbenzene (TPB) microcrystals into four polarized spectra measured with polarizer (V: vertical and H: horizontal) and analyser (V: vertical and H: horizontal), where V and H indicate perpendicular and parallel to the layer of TPB molecules in the crystal, respectively. Resolved spectra were interpreted in terms of the molecular and excimer like (J- and H-dimer) emissions. The origin of the excimer like emissions was discussed in relation to the molecular packing in the crystal. It was shown that polarized crystal fluorescence can provide insight into the excitation/emission process in the crystal. Although preliminary, this study demonstrates the potential of polarized fluorescence to elucidate the luminescent mechanism.

Room-Temperature Synthesis of 1,3,5-Tri(het)aryl Benzene from Nitroalkenes Using Pd(OAc)2: Complete Mechanistic and Theoretical Studies

Herein, a room-temperature catalytic pathway for 1,3,5-tri(het)aryl derivatives from nitroalkenes using simple Pd(OAc)₂ is presented. This newly developed C-C bond-forming methodology takes place in a cascade manner with the initial pallado-Morita-Baylis-Hillman (MBH) type adduct. The broad substrate scopes, functional group tolerance, and different aryl-substituted benzene derivatives make this methodology more attractive. Furthermore, the mechanistic understanding through isolation of intermediates and DFT studies of the catalytic cycle provide requisite insight into the methodology.

Bronsted acidic surfactants: efficient organocatalysts for diverse organic transformations

Organic transformations using efficient, atom-economical, cost-effective and environmentally benign strategies for the construction of diversified molecules have attracted synthetic chemists worldwide in recent years. These processes often minimize the waste production and avoid the use of hazardous flammable organic solvents. Among various green protocols, the procedures using surfactant-based catalytic systems have received a considerable attention in organic synthesis. In this context, Bronsted acidic surfactants have emerged as efficient catalysts for various C–C, C–O, C–N and C–S bond forming reactions. Many of these reactions occur in water, as Bronsted acidic surfactants have a unique ability of creating hydrophobic pocket through micelle formation in aqueous medium and the substrate molecules react efficiently to afford the targeted products in good yields. In the past, Bronsted acidic surfactant combined catalysts successfully displayed their potential to accelerate the reaction rates of diverse organic transformations. This chapter presents a complete overview on Bronsted acidic surfactants catalyzed organic reactions to construct a variety of aromatic and heteroaromatic molecular frameworks.

N-Benzoyl dithieno[3,2-b:2',3'-d]pyrrole-based hyperbranched polymers by direct arylation polymerization

BACKGROUND

Although poly(N-acyl dithieno[3,2-b:2',3'-d]pyrrole)s have attracted great attention as a new class of conducting polymers with highly stabilized energy levels, hyperbranched polymers based on this monomer type have not yet been studied. Thus, this work aims at the synthesis of novel hyperbranched polymers containing N-benzoyl dithieno[3,23,2-b:2',3'-d]pyrrole acceptor unit and 3-hexylthiophene donor moiety via the direct arylation polymerization method. Their structures, molecular weights and thermal properties were characterized via 1H NMR and FTIR spectroscopies, GPC, TGA, DSC and XRD measurements, and the optical properties were investigated by UV-vis and fluorescence spectroscopies.

RESULTS

Hyperbranched conjugated polymers containing N-benzoyl dithieno[3,23,2-b:2',3'-d]pyrrole acceptor unit and 3-hexylthiophene donor moiety, linked with either triphenylamine or triphenylbenzene as branching unit, were obtained via direct arylation polymerization of the N-benzoyl dithieno[3,23,2-b:2',3'-d]pyrrole, 2,5-dibromo 3-hexylthiophene and tris(4-bromophenyl)amine (or 1,3,5-tris(4-bromophenyl)benzene) monomers. Organic solvent-soluble polymers with number-average molecular weights of around 18,000 g mol-1 were obtained in 80-92% yields. The DSC and XRD results suggested that the branching structure hindered the stacking of polymer chains, leading to crystalline domains with less ordered packing in comparison with the linear analogous polymers. The results revealed that the hyperbranched polymer with triphenylbenzene as the branching unit exhibited a strong red-shift of the maximum absorption wavelength, attributed to a higher polymer stacking order as a result of the planar structure of triphenylbenzene.

CONCLUSION

Both hyperbranched polymers with triphenylamine/triphenylbenzene as branching moieties exhibited high structural order in thin films, which can be promising for organic solar cell applications. The UV-vis absorption of the hyperbranched polymer containing triphenylbenzene as branching unit was red-shifted as compared with the triphenylamine-containing polymer, as a result of a higher chain packing degree.

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.

An eco-friendly Pictet–Spengler approach to pyrrolo- and indolo[1,2-a]quinoxalines using p-dodecylbenzenesulfonic acid as an efficient Brønsted acid catalyst

Environmentally benign synthesis of pyrrolo- and indolo[1,2-a]quinoxalines has been achieved at 25 °C by usingp-dodecylbenzenesulfonic acid as a Brønsted acid catalyst.

Single crystal structure analysis via magnetically oriented microcrystal arrays

Single crystal structure determination is possible from a powder sample without preparing a large single crystal.