Synthesis and Photochemistry of Pyrano[2,3-c]pyrazoles

Two different synthetic approaches to the synthesis of pyrano[2,3-c]pyrazoles have been investigated. In one approach, dehydroacetic acid derivatives were treated with phenylhydrazine and methylhydrazine led to the formation of the phenylhydrazones and methylhydrazones, which undergo rearrangement in refluxing acetic acid to diketo-phenylpyrazoles and diketo-methylpyrazoles. Upon treatment with a mixture of acetic and sulfuric acid these compounds isomerize to the phenylpyrano[2,3-c]pyrazol-4-one and methylpyrano[2,3-c]pyrazol-4-one derivatives. In a second approach, phenylhydrazine and methylhydrazine reacted with dimethyl(methoxymethylene)malonate (34) to give phenylpyrazole and methylpyrazole ester derivatives which were converted to phenylpyrazolone and methylpyrazolone by hydrolysis and decarboxylation. C-acylation of these compounds with trans-cinnamoyl chloride gave á,â-unsaturated-4-acetyl-5-hydroxypyrazoles. Bromination of these á,â-unsaturated-4-acetyl-5-hydroxypyrazoles with spontaneous cyclization, followed by dehydrobromination led to pyrano[2,3-c]pyrazol-4-one derivatives, respectively. Phototochemical excitation of 1-phenyl and 1-methylpyrano[2,3-c]pyrazol-4-ones in acetonitrile led to the formation of cis-head-to-tail [2+2] cycloaddition products. Irradiation in ethanol solvent led to photodimerization and to photofragmentation to yield pyrazole ethylesters

Poly(organosilsesquioxanes) in designing electro, photo, and magnetic functional materials

Supervisor: Professor Dr. Yusuke Kawakamiマテリアルサイエンス研究科博

Synthesis and Isolation of Methacrylate- and Acrylate-Functionalized Polyhedral Oligomeric Silsesquioxanes (T₈, T₁₀, and T₁₂) and Characterization of the Relationship between Their Chemical Structures and Physical Properties

Novel organic–inorganic hybrid nanobuilding blocks of methacrylate- and acrylate-functionalized polyhedral oligomeric silsesquioxanes were easily prepared via nucleophilic substitution on octakis­(3-chloropropyl)­octasilsesquioxane, using sodium methacrylate and sodium acrylate, respectively. From a practical standpoint, these cage-rearranged silsesquioxanes (T₈, T₁₀, and T₁₂) could be readily isolated in their pure form with conventional silica gel column chromatography. Octakis­(3-propyl methacrylate)­octasilsesquioxane (T₈) is a colorless, crystalline solid with a melting point of 66.7–67.2 °C, while other cage products are colorless viscous liquids at room temperature. Moreover, we report that the chemical structure/physical property relationship of silsesquioxane cages not only is dependent on the symmetry of the inorganic silsesquioxane core at a given temperature but also is dictated by the organic substituent mobility. Structures of the products were confirmed by ¹H, ¹³C, and ²⁹Si NMR spectroscopy and high resolution electrospray ionization mass spectrometry analysis

Synthesis, characterization, and OLED application of oligo(p-phenylene ethynylene)s with polyhedral oligomeric silsesquioxanes (POSS) as pendant groups

Two new classes of mono- and oligo(p-phenylene ethynylene)s grafted with polyhedral oligomeric silsesquioxanes (POSS) were synthesized via “click” chemistry and palladium-catalyzed Sonogashira cross-coupling. These materials with cubic silsesquioxanes are very robust with excellent thermal stability in air (T_ > 333℃) and exhibited T_g > 80℃. All the compounds showed high photoluminescence with a range of blue emission and quantum yield up to 80% in the solution. Extended π conjugation molecules of oligo-pPEs POSS maintain relatively high PL quantum efficiencies in the solid state, compared to mono-pPEs POSS. A preliminary report is made of some of the materials as multilayer OLED components with active dopants PVK and PBD