Titanium(IV) halides are extensively used in carbon-carbon bond forming reactions; for example, Mukaiyama aldol reactions of aldehydes with silyl enol ethers, Diels-Alder reactions, and carbonyl-ene reactions as a Lewis acid. Low valent titanium halides promote reductive coupling reactions of carbonyl compounds. In most of these reactions, ligands of titanium halides are chloride or bromide. Although titanium(IV) tetraiodide (TiI₄) had been used for the production of metal titanium of high purity, its use was rare in organic synthesis. We have focused on a mild Lewis acidity, reducing and iodination abilities of titanium(IV) tetraiodide, and already reported several reactions such as reductive aldol, Mannich-type reactions, and pinacol coupling reaction. We continued to investigate novel synthetic reactions using the iodotitanation ability of titanium(IV) tetraiodide. We report here titanium(IV) tetraiodide-promoted Prins-type reactions, ring-opening reactions of aziridines and azetidinones, iodo-aldol and Mannich reactions, and iodopyridine and iodoisoquinoline synthesis via iodination-cyclization reactions.

Heterogeneous catalysts are key players in environmentally benign organic synthesis because they can be easily recovered and reused by simple operations. In addition, heterogeneous catalysts can be applied to synthetic tools in next generation, such as flow systems and combinatorial synthesis. We have focused on metal nanocluster catalysts as highly active and robust heterogeneous catalysts and have developed variety of metal nanocluster catalysts for fine organic synthesis. In the course of development, we chose organic polymer as support of metal nanoclusters because organic polymer can provide efficient reaction environment for organic reactions and introduction of various functionality that provide synergistic effect to metal nanocluster catalyst is facile in organic polymers. In this context, we designed both supports and metal nanoclusters in order to realize not only high reactivity and selectivity but also different catalytic functions that cannot be achieved with homogeneous catalyst.

This article describes the design and synthesis of highly functionalized metal nanocluster catalysts, namely polymer incarcerated metal nanocluster catalysts, and their application to aerobic oxidations, asymmetric reactions, tandem reactions and synergistic catalysis.

Precious metal compounds are widely used as catalysts in recent organic synthesis in both academic and industrial researches. Recently, development of new iron-based catalyst systems that can be a substitute of noble metal catalyst is desired from the point of view of scarcity of the element and the toxicity of the precious metal residue in the products. However, design and synthesis of iron catalysts is often difficult due to the existence of multiple spin states in close energy levels. In addition, instability of organoiron species toward air and moisture also prevents the synthesis of catalytically active iron species. In this paper is presented our recent effort to develop the efficient iron catalyst system. First, low-spin design of the iron catalyst that can catalyze the reaction involving two-electron redox pathway is investigated based on the strategy of construction of the disilaferracyclic complexes. Second, novel efficient and easy-to-handle iron catalyst system consisting of iron precursor and isocyanide ligands is developed for the hydrosilylation of alkenes.

Molecular design and development of protein assemblies with functional molecules has recently been intriguing subject in bionanotechnology and biomaterials because protein assemblies can provide unique chemical environments which can immobilize functional substances such as metal ions, metal complexes, nanomaterials, and proteins. In this article, we focus on our recent progress of protein assemblies of cages and crystals as molecular templates for reaction vessels and molecular delivery. First, ferritin engineering for tandem reactions by two different organometallic complexes in the cage and delivery of gaseous molecules using the cage into the cells is reported. Second, protein crystals are developed in the applications as solid catalysis and extracellular matrix by immobilization of metal complexes in the solvent channels of protein crystals. Finally, in vivo protein crystal engineering toward the creation of bio-hybrid solid materials in living cells is described.

Mannopeptimycin is an attractive drug candidate due to its strong antimicrobial activity against drug-resistant strains. However, detailed elucidation of structure-activity relationship and its mode of action has been hampered because the chemical synthesis of the densely functionalized aglycone moiety consisting of cyclic hexapeptide was not established. The key point in the synthesis of the aglycone was the construction of densely functionalized unnatural amino acids, Aiha-A and Aiha-B. This account describes isolation, structural determination of mannopeptimycins, previously reported synthesis of Aiha-A and Aiha-B as well as our short-step, high-yielding synthesis of Aihas leading to the first synthesis of mannopeptimycin aglycone with stereochemistry revision of originally proposed structure.

The development of an innovative strategy for the bond-forming reactions is quite important to construct new molecular structures, efficiently. In this short review, recent examples of carbon-carbon bond formation reactions based on the extrusion of small molecules, such as carbon dioxide and carbon monoxide, using transition metal complexes are described.

The asymmetric dearomatization reaction of phenols and their derivatives has emerged as a powerful method for the construction of enantioenriched cyclic enones, which are frequently found in bioactive natural products and pharmaceuticals. This review focuses on recent progress for construction of quaternary stereocenter based on organocatalytic dearomatization reaction.

Methane is one of the most unreactive hydrocarbons because of its physical and chemical properties. The uses of natural gas (consisting primarily of methane) are limited to the combustion or the reforming process to produce heavier hydrocarbons. From the effective use of natural resources, the direct functionalization of methane via C-H bond activation has been attracted much attention recently. This review described recent developments of C-H bond functionalization of methane by homogeneous catalysis.

Carolacton (1) was isolated from the culture broth of Sorangium cellulosum strain So ce960 and possesses 12-membered macrocyclic lactone with an aliphatic chain bearing a carboxy group at terminal. It exhibits reduction of the number of viable cells in biofilms. In this review, total synthesis, truncated analog synthesis, and biological phenomenon of 1 are described.