1,6-Disila[4.4.4]propellane revisited part 1: Improved synthesis by a mechanistically logical fluorosilane route and its structural aspects including linear stacking along the Si-Si bond in the crystalline state Suguru Kobayashi, Takahiro Sasamori, Yumiko Nakajima, Yasunori Minami, Kosuke Iizuka, Tomoyuki Saeki, Akio Toshimitsu, Hayato Tsuji, Shigehiro Yamaguchi, Aiko Fukazawa, Tomokatsu Kushida, Daisuke Hashizume, Kohei Tamao Bulletin of the Chemical Society of Japan, 2026 This study details a highly significant improvement in the synthesis of 1,6-disila[4.4.4]propellane (1) through the implementation of a mechanistically rationalized fluorosilane route. This efficiency represents a more than 20-fold enhancement over the previously reported method (4% yield). Structural analysis by single-crystal X-ray diffraction revealed its unique columnar packing arrangement in the solid state.
Siloxane-linked tungsten complexes form a flexible metal–organic framework: 1-D channel structure and gas adsorption property Ryo Nakamura, Koichi Nagata, Takahiro Kawatsu, Kazuhiro Matsumoto, Yumiko Nakajima, Takuji Ikeda, Shinya Takaishi, Wataru Kosaka, Hitoshi Miyasaka, Hisako Hashimoto Inorganic Chemistry Frontiers, 2025 A siloxane-linked complex formed a framework with a 1-D channel structure, exhibiting gate-opening adsorption behavior toward gaseous molecules, highlighting its flexibility.
Development of Hydrosilylation Reaction Towards High-Performance Organosilicon Materials Yumiko Nakajima Yuki Gosei Kagaku Kyokaishi Journal of Synthetic Organic Chemistry, 2025 Hydrosilylation reactions have long served as a fundamental technology for the production of organosilicon compounds. Platinum-catalyzed hydrosilylation has long been employed in the industrial process. However, the widespread use of platinum catalysts presents two major challenges: Their high cost due to the scarcity of platinum, and their limited ability to achieve highly selective synthesis of high-performance organosilicon materials. Therefore, the need to develop alternative catalysts that are both highly selective and/or environmentally sustainable has become increasingly urgent in the silicone industry. To address these issues, we have developed new hydrosilylation catalysts tailored for specific industrial needs.
Z-Selective Semihydrogenation of Internal Alkynes Catalyzed by Phenanthroline-Based PNNP-Fe(II) Complexes Tao Wang, Yoshihito Kayaki, Hiroto Fujisaki, Hajime Kawanami, Yoshihiro Shimoyama, Masaru Yoshida, Yumiko Nakajima Chemcatchem, 2025 Fe(II) complexes bearing a phenanthroline‐based tetradentate PNNP ligand (2,9‐bis[(diphenylphosphino)methyl]‐1,10‐phenanthroline, 2,9‐bis[(dicyclohexylphosphino)methyl]‐1,10‐phenanthroline) were applied as metal–ligand cooperative catalysts to promote semihydrogenation of internal alkynes. The reaction proceeded with atmospheric H2 at a catalyst loading of 2–5 mol%/Fe to selectively produce the corresponding Z‐alkenes. The reactions exhibited good functional group compatibility toward substrates with various substituents, including polar ester and cyano groups, as well as a coordinating sulfur‐containing thiophene moiety.
Rapid Depolymerization of Polyester Fibers: Dimethyl Carbonate-Aided Methanolysis Combined with the Ball-Milling Approach Shinji Tanaka, Maito Koga, Azusa Togo, Atsuko Ogawa, Hibiki Ogiwara, Tetsuya Yamamoto, Yumiko Nakajima, Masaru Yoshida ACS Sustainable Chemistry and Engineering, 2025 Although polyethylene terephthalate (PET) bottles are conventionally reused using a material recycling process, the high content of impurities, such as dyes, pigments, and/or other fibers in the PET fibers, complicates the process. Chemical recycling is a promising method for PET fibers, but the depolymerization of PET fibers under mild conditions is still challenging due to their high crystallinity from the yarn-making process. Herein, we developed a rapid and efficient depolymerization process for PET fibers at room temperature by combining dimethyl carbonate (DMC)-aided methanolysis (DCAM) with a ball-milling (BM) approach. Compared with DCAM of PET fibers in a flask, the BM approach reduced not only the reaction time but also the amount of DMC required, which are key advantages toward practical application. To clarify the acceleration effect of BM on the depolymerization, PET fiber residues after the reaction were analyzed by gel permeation chromatography, differential scanning calorimetry, X-ray scattering, and solid-state NMR. The findings suggested that BM promotes the phase transformation of PET from its crystalline phase to its amorphous phase. In addition, BM induces efficient contact of the surface of the polymer with the catalyst/reagent, even in heterogeneous reaction media.
Si-Cl σ-Bond Cleavage by an Fe(0) Complex with Two Steps of One-Electron Transfer toward Hydrosilane Formation from Tetrachlorosilane Yumiko Nakajima, Kosuke Iizuka, Tomohiro Takeshita, Shiori Fujimori, Yoshihiro Shimoyama, Kazuhiko Sato, Masaru Yoshida, Shao-Fei Ni, Shigeyoshi Sakaki Jacs Au, 2025 High Resolution Image Download MS PowerPoint Slide Iron catalysts exhibit unique reactivity that has not been found in precious metal catalysts. Herein, a new strategy for strong Si–Cl σ-bond cleavage of tetrachlorosilane (SiCl 4 ) was successful using [{Fe(PNNP)} 2 (μ-N 2 )] (PNNP = 2,9-bis((diphenylphosphino)methyl)-1,10-phenanthroline). The resulting oxidative addition product [Fe(SiCl 3 )(Cl)(PNNP)] was fully identified, establishing the first example of Si–Cl σ-bond cleavage using an air-sensitive iron(0) complex. Theoretical study revealed that Si–Cl σ-bond cleavage occurs with radical character through two steps of single-electron transfer from [Fe(PNNP)] to the Si–Cl σ* antibonding orbital, which differs from usual concerted oxidative addition. This σ-bond cleavage reaction was successfully applied to HSiCl 3 formation from SiCl 4 and 1,10-dihydroanthracene via hydrogen atom transfer (HAT). Thus, we succeeded in performing Si–Cl σ-bond cleavage using the Fe(0) complex and its application to hydrosilane synthesis from SiCl 4 using a mild hydrogen source. This iron(0) complex is expected to be active as catalyst for other difficult reaction.
One-Step Esterification of Phosphoric, Phosphonic and Phosphinic Acids with Organosilicates: Phosphorus Chemical Recycling of Sewage Waste Yuki Naganawa, Kei Sakamoto, Akira Fujita, Kazuya Morimoto, Manussada Ratanasak, Jun‐ya Hasegawa, Masaru Yoshida, Kazuhiko Sato, Yumiko Nakajima Angewandte Chemie International Edition, 2025 Global concerns regarding the depletion and strategic importance of phosphorus resources have increased demand for the recovery and recycling. However, waste‐derived phosphorus compounds, primarily as chemically inert phosphoric acid or its salts, present a challenge to their direct conversion into high‐value chemicals. We aimed to develop an innovative technology that utilizes the large quantities of sewage waste, bypasses the use of white phosphorus, and enables esterification of phosphoric acid to produce widely applicable phosphate triesters. Tetraalkyl orthosilicates emerged as highly effective reagents for the direct triple esterification of 85 % phosphoric acid, as well as the esterification of organophosphinic and phosphonic acids. Furthermore, we achieved esterification of recovered phosphoric acid with tetraalkyl orthosilicate, thus pioneering a recycling pathway from sewage waste to valuable phosphorus chemicals. Experimental and theoretical investigations revealed a novel mechanism, wherein tetraalkyl orthosilicates facilitate multimolecular aggregation to achieve alkyl transfer from tetraalkylorthosilicate to phosphoric acid via multiple proton shuttling.
Catalytic thiolation-depolymerization-like decomposition of oxyphenylene-type super engineering plastics via selective carbon–oxygen main chain cleavages Yasunori Minami, Sae Imamura, Nao Matsuyama, Yumiko Nakajima, Masaru Yoshida Communications Chemistry, 2024 As the effective use of carbon resources has become a pressing societal issue, the importance of chemical recycling of plastics has increased. The catalytic chemical decomposition for plastics is a promising approach for creating valuable products under efficient and mild conditions. Although several commodity and engineering plastics have been applied, the decompositions of stable resins composed of strong main chains such as polyamides, thermoset resins, and super engineering plastics are underdeveloped. Especially, super engineering plastics that have high heat resistance, chemical resistance, and low solubility are nearly unexplored. In addition, many super engineering plastics are composed of robust aromatic ethers, which are difficult to cleave. Herein, we report the catalytic depolymerization-like chemical decomposition of oxyphenylene-based super engineering plastics such as polyetheretherketone and polysulfone using thiols via selective carbon–oxygen main chain cleavage to form electron-deficient arenes with sulfur functional groups and bisphenols. The catalyst combination of a bulky phosphazene base P4-tBu with inorganic bases such as tripotassium phosphate enabled smooth decomposition. This method could be utilized with carbon- or glass fiber-enforced polyetheretherketone materials and a consumer resin. The sulfur functional groups in one product could be transformed to amino and sulfonium groups and fluorine by using suitable catalysts.
Depolymerization of Polyester Fibers with Dimethyl Carbonate-Aided Methanolysis Shinji Tanaka, Maito Koga, Takashi Kuragano, Atsuko Ogawa, Hibiki Ogiwara, Kazuhiko Sato, Yumiko Nakajima ACS Materials Au, 2024 Polyester fibers, comprising mostly poly(ethylene terephthalate) with high crystalline content, represent the most commonly produced plastic for ubiquitous textiles, and approximately 60 million tons are manufactured annually worldwide. Considering the social issues of mismanaged waste produced from used textile products, there is an urgent demand for sustainable waste polyester fiber recycling methods. We developed a low-temperature, rapid, and efficient depolymerization method for recycling polyester fibers. By utilizing methanolysis with dimethyl carbonate as a trapping agent for ethylene glycol, depolymerization of polyester fibers from textile products proceeded at 50 °C for 2 h, affording dimethyl terephthalate (DMT) in a >90% yield. This strategy allowed us to depolymerize even practical polyester textiles blended with other fibers to selectively isolate DMT in high yields. This method was also applicable for colored polyester textiles, and analytically pure DMT was isolated via depolymerization and decolorization processes.
