Organofluorines are of great importance in broad research fields including pharmaceutical sciences and materials chemistry. Despite the significance, it is not always easy to synthesize organofluorines due to limited synthetic methods. We recently developed a new approach for the preparation of organofluorines via single C-F transformations of benzotrifluorides triggered by hydride abstraction of the ortho-hydrosilyl group. Indeed, we found that single C-F allylation took place by the treatment of a mixture between benzotrifluorides having a diphenylsilyl group and allyltrimethylsilane with triphenylmethylium tetrafluoroborate in dichloromethane and 1,1,1,3,3,3-hexafluoro-2-propanol(HFIP)to provide difluoromethylenes bearing a fluorodiphenylsilyl group. The resulting fluorosilyl group successfully served in the C-Si transformations such as Hiyama cross-coupling. Then, we succeeded in the C-F thiolation of o-(hydrosilyl)benzotrifluorides catalyzed by Yb(OTf)₃ using trityl sulfides as an all-in-one reagent for generating a trityl cation and thiolate anions. Treatment of benzotrifluorides having a diphenylsilyl group with trityl chloride afforded diverse difluorobenzyl chlorides without Lewis acid catalysis. We also found that the hydride reduction of fluorosilyl group proceeded smoothly using lithium alminum hydride leaving the difluoromethylene group untouched. The resulting hydrosilyl group served in the further C-F transformations to furnish various highly functionalized benzyl fluorides. These C-F transformations allowed us to synthesize a wide range of novel organofluorines which are difficult to prepare by conventional methods.

The use of “gaseous molecule surrogates,” which can produce gaseous compounds by chemical reactions or physical stimuli, has been attracting attention as a beneficial tool to realize safe and convenient organic synthesis. We have engaged in the development of novel surrogates of gaseous molecules, especially focusing on carbon monoxide (CO), and in their application to synthetic organic chemistry. This article describes our recent progress on the development of catalytic organic reactions utilizing gaseous molecule surrogates with high safety and practicality. Detailed mechanism of CO generation from phenyl formate as a CO surrogate has been elucidated both experimentally and theoretically, which led us to develop a series of Pd-catalyzed carbonylative reactions such as room-temperature alkoxycarbonylation and rapid fluorenone formation. We have also exploited the novel synthetic role of potassium metabisulfite as a sulfur dioxide (SO₂) surrogate to selectively afford sulfur-containing compounds with various valences, based on achieving the selective formation of cyclic sulfonamides and sulfinamides, symmetrical sulfones, and symmetrical sulfides. It is noteworthy that newly developed modular synthesis-like reactions utilizing both CO and SO₂ surrogates were safely conducted with ordinary glassware and were scalable to gram-scale production without any difficulties, indicating their potential use on facile derivatization in medicinal chemistry and on large-scale synthesis.

Fluorescent molecules have been widely utilized in scientific researches, medical uses a industrial purposes. To develop fluorophores with useful and unpredictable functions, our group have focused on natural products, and identified fluorescent natural products, Amarastelline A and Nigakinone. For the evaluation of those functions as a fluorophore and the development novel fluorescent sensors, we synthesized various derivatives of these common structures, canthin-5,6-dione and 1,5-naphthyridin-2(1H)-one. Among them, novel polarity-sensitive fluorophore, which showed the shift of fluorescence maximum wavelength by the change of solvent polarity, could be obtained. To apply this function to the study of biomolecule interaction, C5 peptide, which could interact calmodulin, labelled with this fluorophore, was synthesized, and its interaction with calmodulin could be detected by the ratio the fluorescence intensities at two fluorescent maximum wavelengths. Our findings indicated the usefulness of natural products for the development of novel fluorescent molecules, as well as the versatilities of canthin-5,6-dione and 1,5-naphthyridin-2(1H)-one.

Although a variety of polyaromatic hydrocarbons (PAHs), describing graphene segments containing unsaturated hexagonal rings, exhibit a predominantly electron-rich character, fullerenes with unsaturated hexagonal and pentagonal rings are electron-deficient and can thus be employed as n-type materials. The pyracylene skeleton, a key segment of fullerenes, is particularly interesting due to its antiaromatic character and high electron affinity. We have recently reported short-step synthesis of PAHs that contain a pyracylene moiety, which are based on twofold Scholl cyclization. The thus obtained PAHs exhibit not only an electron-deficient character, but also unique reactivity, which furnished compounds with a curved or planar π-surface and distinct emission behavior in the solid state. During our studies on the synthesis of PAHs, we have discovered a one-pot domino cross-Scholl reaction in which tetracene reacts with six molecules of benzene to form eight C-C bonds. This unprecedented reaction should contribute to the short-step synthesis of luminescence materials with intense excimer-type emission. In addition, n-type organic materials are of paramount importance for the generation of flexible thermoelectric modules. We briefly introduce our synthetic studies toward conductive π-conjugated nickel bis- (dithiolene) complexes to develop solution-processable and air-stable n-type thermoelectric films with improved performance. The results presented here should contribute to the facile synthesis of advanced materials with potential applications in flexible thermoelectric generators.

Polypeptides are a promising class of polymers that can be used to develop new biodegradable and biocompatible materials from the viewpoint of sustainable development goals as the overall aim. Natural structural proteins such as fibroin, collagen, elastin, and resilin have a specific repeating sequence, which exhibit excellent mechanical properties desirable for use in biomedical applications. However, the sequence-ordered polymerization technique for polypeptide has not been sufficiently developed. This review describes one-pot synthesis of alternating peptides via polycondensation of an imine with an ambident molecule comprising isocyanide and carboxylic acid. The elemental reaction of the polycondensation is Ugi four component condensation reaction for catalyst-free dipeptide synthesis. The molecular weights (M_ws) of the obtained polymers were estimated by DOSY-based technique. As the applications of our invention, we newly created the viscoelastic alternating peptides with shear-induced adhesion behaviors, the alternating peptide-based surfactants, and the thermo-responsive hydrogel comprising alternating peptide skeleton as the cross-linking points. We also investigated the impact of polypeptide sequence on thermo-responsiveness. Because of the skeletal diversity and the good scalability of preparation, alternating peptides may be regarded as useful framework for the development of peptide-based smart materials in the future.

The development of controlled polymerization such as RAFT polymerization has enabled the synthesis of macromolecules with well-defined structures. Recently, control over polymerization processes has been achieved through regulation of chain growth with various external stimuli. This review highlights the interconversion between living radical and cationic polymerization using external stimuli. Photochemical and electrochemical stimuli are effective to switch the polymerization mechanism and the monomer selectivity in situ.