Boron-containing π-conjugated compounds have long attracted attention in the field of materials chemistry because of their interesting optical and electrochemical properties. For example, boron-dipyrromethene dyes have been used for fluorescent dye for labeling proteins and DNA because of their high absorption coefficient and absolute PL quantum yield and stability in water. On the other hand, their applications as an organic electronic material have been intensively reported. However, since the carbon-boron bond is easily cleaved during device operation, their practicality has been questioned in the industry. In contrast, we have succeeded in developing a new class of boron-containing π-conjugated compounds with practical durability based on the strategy of stabilizing the carbon-boron bond from both entropy and enthalpy aspects by introducing boron atoms together with oxygen or nitrogen atoms in the ring junction of the polycyclic skeleton, which had been difficult to construct by conventional organic reactions. The key to success is the use of tandem bora-Friedel-Crafts reaction, which provides short-step and large-scale synthesis of the new boron-based compounds. This manuscript focuses on their molecular design, synthesis, and application as an OLED material.

Since the carbon-fluorine (C-F) bond exhibits a high bond dissociation energy, chemical transformation involving its cleavage (C-F bond activation) has been difficult and a challenge in synthetic organic chemistry. As one solution to this problem, we established a new and efficient methodology for C-F bond activation under mild reaction conditions by taking full advantage of transition metal-mediated β- and α-fluorine elimination processes. In these studies, we investigated organometallic elementary steps such as (i) oxidative cyclization, (ii) nucleophilic addition, and (iii) electrophilic addition, as bond-forming processes that produce intermediates suitable for fluorine elimination. By combining these processes with fluorine elimination, we systematically developed various synthetic reactions via allylic and vinylic C-F bond activation of fluoroalkenes. In addition, fluorophilic boron or silicon compounds were found to serve as fluorine captors, thereby promoting catalytic reactions by regenerating active species from inert metal fluorides, which were often generated in metal-mediated fluorine elimination.

Lanthanides contain 15 elements from lanthanum to lutetium in a 4f block, and their distinctive feature is their large ionic radii, enabling them to have high coordination numbers in contrast to transition metals. Among these lanthanide complexes, cerium stands out due to its unique redox chemistry by having two stable oxidation states, cerium(III) and cerium(IV). Although cerium(IV) complexes are well-known as potent stoichiometric oxidants in organic synthesis, they exhibit catalytic performances upon introducing suitable supporting ligands in the cerium coordination sphere as well as utilizing their photo-responsive characters. Our exploration of cerium catalysis is summarized in this review, with emphasis on two characteristic features of cerium complexes, activation of dioxygen by cerium(III) to form peroxocerium(IV) species and photo-reduction of cerium(IV) carboxylates by cleaving the cerium(IV) -ligand covalent bonds to generate organic radicals. Characterization of cerium(III) and cerium(IV) complexes with elucidating the transitions of cerium species during the redox processes is included to propose the comprehensive reaction mechanisms. In the initial part of this review, cerium-catalyzed alcohol oxidation by two catalytic systems, i.e. 2,2,6,6-tetramethylpiperidine-N-oxyl(TEMPO)-assisted and -free conditions is described with clarifying the pivotal roles of TEMPO and the supporting phenoxide ligands during the catalytic cycle. In the later part, utilization of the photo-responsivity of cerium(IV) carboxylate clusters is summarized, and their UV-Vis measurements, DFT studies, and photo-catalytic transformation of carboxylic acids in the presence of cerium(IV) complexes are disclosed.

The bioinspired catalyst system was developed in the interdisciplinary fields of bioinorganic chemistry and catalytic chemistry. In nature, enzymes catalyze various molecular transformations under mild conditions with a high efficiency and selectivity. Therefore, we can learn about many excellent systems from nature. As for the catalyst design, a metal complex inspired by the active site of a metal enzyme has been developed and the combination of the metal complex with a redox system should form an excellent catalytic system. Based on this concept, we can use various redox systems such as electrochemistry and photo-excited chemistry to construct a catalyst system. Among the metal complexes inspired from natural metal enzymes, the cobalt ion containing the B₁₂ derivative is the focus on this account. Organometallic B₁₂ complexes are unique metal complexes having a cobalt-carbon σ-bond that exist in biological systems. Cleavage of the metal-organic σ-bond initiates many B₁₂ dependent enzymatic reactions. Based on the unique properties of alkylated cobalt complex, many B₁₂-inspired reactions have been developed. Here the visible light driven B₁₂ inspired reaction for the synthesis of various compounds from organic halides as carbon source were summarized, and the combination of the B₁₂ derivative as redox catalyst in electroorganic synthesis for the conversion of various trichloromethylated organic compounds to amides was reviewed.

Lipids have extremely diverse molecular structures and possess a variety of bioactivities related to life phenomena. However, the scope of lipid synthesis is limited, although chemical syntheses targeting each molecular species have been reported. This paper presents the divergent synthesis of phospholipids using the phosphoramidite method developed by the authors. Using this method, the authors have reported the synthesis of cardiolipin, phosphatidylglycerol, and phosphatidylcholine. Among these synthesized lipids are lysocardiolipin and its ether-type analogues, as well as photoreactive probes intended to analyze their interactions with proteins. The application of the synthesis of various phospholipid analogs to the analysis of physiological functions of lipids is then discussed. In particular, the molecular interactions of cardiolipin with cytochrome c, the substrate specificity of cardiolipin remodeling synthesis by the transacylase tafazzin, and complementation studies of phosphatidylglycerol in cyanobacteria are discussed. In each case, the structure-activity relationship studies were based on systematic chemical syntheses of phospholipids and were carried out on the basis of a careful design not only of the lipid molecules to be synthesized, but also of the corresponding synthetic routes.

Recently, heavier group-15 (pnictogen) element compounds with Lewis acidity modulated by organic substituents have been attracting attention. This short review focuses on the recent developments in Lewis acids and their catalytic activity in organo-antimony (Sb) compounds.