One of the greatest challenges in modern chemistry is to perform efficient transformations of organic molecules under environmentally friendly conditions with the aid of catalyst. In the past few decades, high performance catalysts have been designed for a variety of organic transformations. By using an appropriate catalyst, a number of reactions that would not usually proceed have been accomplished and ingenious reaction selectivities have been attained. These developments stimulated remarkable progress in the field of catalytic organic chemistry. Under these situations, we focused our attention on transition metal-catalyzed dehydrogenative transformations of organic molecules based on the cooperative catalysis by iridium and a functional ligand. In this paper, our recent investigations on (1) dehydrogenative oxidation of alcohols into carbonyl compounds, (2) hydrogen storage systems based on the reversible interconversion between saturated N-heterocyclic compounds and unsaturated aromatic N-heterocyclic compounds by catalytic dehydrogenation and hydrogenation, and (3) efficient hydrogen production from methanol-water solution under very mild conditions, will be reported.

The reaction of a copper salt and an α-bromocarbonyl compound, which is a great initiator for atom-transfer radical polymerizations or re-oxidant for low valent metal species, produces an α-radical species. But there are a few reports on tertiary-alkylations by using α-bromocarbonyl compounds as a tertiary-alkyl source. Although alkylation is important and fundamental chemistry in organic chemistry, tertiary-alkylation is still recognized as a challenging reaction. In our continuous studies on α-bromocarbonyl chemistry for tertiary-alkylation, we have established the Cu-catalyzed reaction systems including, A) tert-alkylative substitution reactions, B) formal cycloaddition reactions, C) cross-coupling type reactions, and D) divergent reaction. In this manuscript, I will introduce our methodology to control α-radical species in the presence of copper catalyst to realize diverse reactions to synthesize tertiary-alkylated olefins and cyclic compounds, and cross-coupling type reaction to load fluorine atom and amino groups.

Our total syntheses of lycopodium alkaloid lycodine (1), and its unsymmetric dimmer complanadines A (3) and B (4) were described. The bicyclo[3.3.1]nonane core structure of lycodine was constructed by regioselective Diels-Alder and intramolecular Mizoroki-Heck reactions. A late-stage coupling reaction of the lycodine units, pyridine N-oxide (+)-17 and aryl bromide (+)-16, through C-H arylation at the C1 position of (+)-17 provided the unsymmetric dimer structure. This strategy significantly simplified the construction of the dimeric architecture and functionalization. Total syntheses of complanadines A (3) and B (4) were achieved by adjusting the oxidation level of the bipyridine mono-N-oxide (+)-18. The diverse utility of this common intermediate (+)-18 suggests a possible biosynthetic pathway of complanadines in nature. Both enantiomers of lycodine (1) and complanadines A (3) and B (4) were prepared in sufficient quantities. The effect on neuron differentiation of PC-12 cells with human astrocytoma cells culture medium was evaluated.

Arynes with a highly reactive carbon-carbon triple bond are multipotent intermediates useful for preparing various multisubstituted arenes. To further enhance the synthetic utility of arynes, we have developed a wide range of synthetic methods involving aryne intermediates, including novel methods for aryne generation from o-sulfinylaryl triflates and o-iodoaryl triflates using phenyl or silylmethyl Grignard reagent, respectively. These methods allowed for the generation of new types of aryne intermediates that enabled facile syntheses of a wide variety of multisubstituted arenes such as aryl triflates, anilines, and benzoheterols. We also developed several novel transformations involving C-S or C-P bond formation via aryne intermediates, such as thioamination using sulfilimines, and several methods for preparing various o-silylaryl triflate-type aryne precursors that were difficult to be achieved by the conventional methods. These methods were demonstrated useful for preparation of a diverse range of multitriazoles and multisubstituted o-(arylthio)anilines by modular syntheses.

The glycan plays an important role in cellular recognition in living system by utilizing “cluster effect” and “pattern recognition”. In order to understand the structure-function relationship of glycan to a full extent, the mimicry of these effects by chemical method is in demand. We combined the strain-promoted alkyne-azide cycloaddition and our original RIKEN click reaction to synthesize homogeneous and heterogeneous glycocluster chemically on the albumin template. With these glycoclusters, specific cellular recognition could be achieved both in vitro and in vivo, depending on the lectin expression on the target cells. We also accomplished the first organ-selective metal-catalyzed organic reaction in living animal using the glycocluster system.

The rice blast fungus Pyricularia oryzae is a causative agent of rice blast decease. P. oryzae produces several salicylaldehyde-type phytotoxins depending on the fermentation method: i.e., pyriculol (1), dihydropyriculol (2) and pyriculone (5) from shaking cultures; and pyriculariol (8) and dihydropyriculariol (9) from aeration and agitation cultures in a soy sauce-sucrose medium. Chemical studies of these phytotoxins including total synthesis, structure-elucidation, biosynthesis and structure-activity relationships are described. The absolute configuration of pyriculol (1) and epipyriculol (3) were established by the total synthesis of possible diastereomers. (R)-Pyricuol (7) has a nature-identical configuration as demonstrated by preparation of both enantiomers from (R)- and (S)-lactate respectively, via [2,3]-Wittig rearrangement and Stille coupling reactions. In contrast, natural pyriculariol (8) and dihydropyriculariol (9) are produced as racemates by the chiral synthesis from l-rhamnose (35) using a protective groups-free Stille coupling reaction under microwave irradiation. Biotransformation of the deuterio-labeled compounds indicated triene-aldehyde 33 as a putative key biosynthetic intermediates of the phytotoxins. Foliar application of the compounds on rice leaves revealed that both a salicylaldehyde and a side chain residues are important for the necrotic activity. In conclusion, the blast fungus P. oryzae produced optically active phytotoxins 1 and 2, as well as racemic phytotoxins 8 and 9, depending on the culture conditions. This research provides an interesting example of CH₂OH and CHO groups interconversion occurring at the later stage of phytotoxin biosynthesis.

Azavinyl carbene intermediates are prepared by ring-opening of azole compounds in the presence of Rh catalyst. The intermediates have been used for synthesis of various nitrogen-containing compounds. The present review shows the recent reports for the molecular transformations of triazoles and tetrazoles bearing electron withdrawing groups.

In 1959, the rearrangement of vinylcyclopropane to cyclopentene was reported, which called as “vinylcyclopropane rearrangement” in present. Due to its harsh condition, the rearrangement has been not diligently applied to synthetic chemistry. Recently, Lewis acid-mediated reaction under very mild condition has been developed, which has a wide substrate scope to provide attractive building blocks such as spirooxindole and spiroindanone.

Two dimensional Covalent Organic Frameworks (2D COFs) are new porous materials synthesized from only organic molecules. The 2D COFs consist of light elements that can form strong covalent bonds. The properties of 2D COFs such as pore size, shape and character are easily controlled. The 2D COFs are expected to be applied for a gas storage, an electrochemical device and so on. This review summarized the characteristics and new synthetic methods of 2D COFs.