The studies on nickel(0)-catalyzed three-component reactions via C-H and C-C bond activation were described. Highly regio- and stereoselective cross-trimerization of alkynes proceeded to give the corresponding 1,3-diene-5-yne by combination of triisopropylsilylacetylene and identical or distinct two alkynes via selective terminal C-H bond activation of triisopropylsilylacetylene in the presence of Ni(cod)2/phosphine catalyst. The methodology could be also extended toward the three-component reaction among two alkynes and a norbornene to give the 1,5-enyne. On the other hand, our interest also focused on three-component reductive coupling reaction between ring-strained cyclic alkene, aryl aldehyde and silane. Using methylenecyclopropane, reductive coupling reaction with aryl aldehyde and triisopropylsilane proceeded to yield silylated allylic alcohols via C-C bond cleavage of methylenecyclopropane ring in the presence of Ni(cod)2/NHC catalyst. We also found an unprecedented three-component reductive coupling via aromatic C-H bond activation of aryl aldehyde at the ortho position by combination with norbornene and triisopropylsilane leading to silylated indanol using Ni(cod)2/NHC catalyst.
Benzo[c]phenanthridine alkaloids are distributed in Papaveraceous and Rutaceous plants and classified into two categories of fully aromatized bases and partially hydrogenated bases(B/C-cis-11-hydroxyhexahydrobenzo[c]phenanthridine skeleton). They have long history, in which the first isolation of chelidonine, a partially hydrogenated base, from Papaveraceous plant, was reported in 1839. Over a century later nitidine and fagaronine, O4-type fully aromatized bases isolated from Rutaeceous plant, attracted much attention because of their antitumor activity. At present, a variety of pharmacological effects are recognized in natural and unnatural species. We, about forty years ago, started synthetic studies on fully aromatized bases focusing on structure-activity relationship of antitumor activity and succeeded in establishing widely-applicable synthetic methods. Recently the enantioselective synthesis of chelidonine was completed. Thus, in this review, we present our chemical history for the synthesis of benzo[c]phenanthridine bases.
Development of organic semiconducting materials based on π-conjugated systems for use in organic field-effect transistors (OFETs) has become an active area of research. We have designed and synthesized a series of electronegative units: Carbonyl-bridged bithiazole, dialkyl-substituted naphtho[2,3-c]thiophene-4,9-dione, alkyl-substituted dioxocyclopenta[b]thiophene, and dicyanomethylene-substituted cyclopenta[b]thiophene. The electronegative π-conjugated systems containing these units have been synthesized as potential active materials for air-stable and/or solution-processable n-type OFETs. Electrochemical measurements revealed that the annelation of the electron-withdrawing group contributes both to lowering the lowest unoccupied molecular orbital energy level and to stabilizing the formation of anionic species. Some of compounds are sufficiently soluble to realize the fabrication of their thin films through a solution technique. These electronegative compounds exhibited n-type semiconducting behavior not only in vacuum but also under air-exposed conditions.
Biologically active small molecules have increasingly been used in plant biology to dissect and understand biological systems. Plant hormones are essential factors for normal plant growth and therefore the regulation of their functions causes drastic changes in plant phenotypes. Since small molecules that bind to biosynthesis enzymes and reduce their ability can mimic mutations in plant hormone biosynthesis, plant hormone biosynthesis inhibitors are now widely used in plant physiology and genetics. Here we report our trial for design and synthesis of functional regulators of plant hormones (brassinosteroids, abscisic acid, strigolactones, and gibberellins) and their application to genetics. Our final goal is to use both chemicals and genes for the improvement of crop and biomass production.
Studies on air-stable organic neutral radicals have a history of about 110 years since the first synthesis of triphenylmethyl radical. Physical properties of organic neutral radicals have given substantial far-reaching effects and inspirations for development of molecule-based functionality materials. For the last two decades, we have designed and synthesized novel air-stable organic neutral radicals based on phenalenyl known as an odd-alternant hydrocarbon neutral radical. These radicals possess extremely delocalized electronic-spin natures and high redox abilities. Utilization of high redox ability of the radicals for charge-discharge processes has realized new secondary batteries with high discharge capacity exceeding those of the high-performance lithium-ion secondary batteries. In this review, we describe design and synthesis of our phenalenyl-based stable neutral radicals, their dynamic electronic-spin physical properties, and our challenges for application to secondary batteries.
Schiff-base is a useful tool for construction of a variety of functional compounds owing to its synthetic utility and versatility. Desired cyclic and acyclic Schiff base compounds were selectively obtained in appropriate condition. Coordination sphere provided by Schiff base compound is suitable for metal ion binding to form mono- and di-nuclear metal complexes. Unique properties of dicobalt complexes with Schiff-base ligand were developed in this study. Supramolecular functions of dicobalt complexes based on reversible redox change of metal centers accompanied with structural switching were reported. Furthermore, unique catalysis of dialkylated cobalt complex such as carbon-carbon bond formation and DNA scission were described.
Carbon-oxygen bond formation reaction is one of the most important methods in organic synthesis. In recent years some efficient oxidations using molecular oxygen have been reported. In this review, catalytic methods using copper or palladium complexes and metal-free radical method for installing oxygen-functionality are discussed.