Transition metal-catalyzed cross-coupling reactions are a powerful method to form chemical bonds. Conventionally, haloarenes has been used as the most reliable aryl electrophiles in cross-coupling. Recent studies in the cross-coupling arena have enabled to employ unconventional but ubiquitous aryl electrophiles such as phenol and aniline. With this trend of organic synthesis, cross-coupling reactions using aromatic carboxylic acid derivatives such as esters as aryl electrophiles have gained considerable attention as a de novo and efficient method to construct C-C and C-heteroatom bonds. In order to realize this particular transformation, it is important to develop and design transition metal catalysts, those are active toward the scission of ester C-O bonds and decarbonylation. In this review, we describe the progress of catalytic decarbonylative cross-coupling of aromatic esters including chronological aspects and mechanistic considerations.

A series of half-sandwich ruthenium, rhodium, and iridium complexes with chelating amine ligands have been established as metal-ligand cooperative bifunctional catalysts directed to transfer hydrogenation of ketones. The catalytic functions can be extended to the spontaneous hydrogen evolution from formic acid and hydrodefluorination (HDF) of fluoroarenes, based on the fundamental studies of hydridoiridium complexes with fluorinated sulfonyldiamine ligands. Iridium catalysts with N-trifluoromethylsulfonyldiamine are effective for dehydrogenation of formic acid at ambient temperature in the absence of hydrogen acceptors. Related hydridoiridium complexes with fluoroarylsulfonyl substituents are susceptible to intramolecular HDF and the subsequent orthometallation. Application to the catalytic HDF of a range of fluoroarenes is successfully achieved under transfer hydrogenation conditions using bifunctional iridium complexes.

Nucleophilic substitution reactions on the sp²- or sp³-hybridized carbon, including formal substitution such as addition-elimination sequence, are one of the fundamental transformations in organic synthesis. Compared with the addition reactions, development of catalytic enantioselective substitution reactions is still rare. This account summarizes our recent efforts to solve the problems by using chiral phosphoric acid catalysts. The first topic is the catalytic kinetic resolution of racemic secondary alcohols by an addition-elimination type acylation reaction. The desymmetrization of σ-symmetrical acid anhydrides is also described. The second topic is the enantioselective intramolecular S_N2' reaction. We made clear that the choice of the leaving group is quite important. The last topic is the catalytic kinetic resolution of racemic β-aminoalcohols by nucleophilic benzylation reaction. Chiral phosphoric acid works as a nucleophilic catalyst to form the corresponding phosphonate in situ as a chiral electrophilic intermediate.

Herein, Cu-catalyzed transformations using allenes as substrates are described. First, the borylative transformations of allenes are summarized including hydroboration, boraallylation, and boraformylation. We next deal with the silylative transformations of allenes such as silacarboxylation and silylative allylation of carbonyl compounds. The transformation involving the hydrocupration to allenes are also described. Hydrohydroxymethylation, hydrocarboxylation and hydroallylation were achieved. In each section, the synthesis and characterization of borylcopper, silylcopper and hydridocopper complexes which are important intermediates are briefly introduced.

Nitrogen is essential for all living organisms. The Haber-Bosch process developed in the early 1900s currently produces ammonia from N₂ in the air and H₂ primarily derived from natural gas over a heterogeneous iron catalyst. Much of the ammonia is used to make agricultural fertilizers for food crops. However, this process requires high temperatures and pressures (ca. 500 ℃ and > 100 atm). In contrast, some nitrogenase-containing microbes are able to reduce N₂ to ammonia at ambient conditions. In the middle 1900s, science of both chemical and biological nitrogen fixation has begun to grow rapidly by cooperation between chemistry and biology towards more sustainable approaches to ammonia synthesis and elucidation of biological nitrogen fixation at molecular levels. This review summarizes the up-to-date research history and perspective of the growing science of nitrogen fixation, leading to development of new ways to nab nitrogen from the air to make fertilizers and produce organo-nitrogen compounds as well as the transfer of the nitrogen-fixing symbiosis to food crops like wheat and rice by plant biotechnology.

PROTACs (proteolysis-targeting chimeric molecules), which comprise a target protein ligand, an E3 ubiquitin ligase ligand and a linker, induce selective degradation of the target protein by recruiting the E3 ubiquitin ligase. This approach is attracting attention as an alternative of traditional inhibitor-based therapeutics by small molecules. This review briefly summarizes the development and advances of PROTACs.

Knots play important roles at the molecular scale as well as in our lives. Although more than 6 billion prime knots are predicted theoretically, only four knot topologies (3₁, 4₁, 5₁, and 8₁₉) have been synthesized with small molecules to date. This review summarizes the recent innovative synthetic strategies toward the elaborately braided molecular knots.

C-C coupling reaction is a fundamental process for construction of organic molecules. From the view point of environmentally benign organic synthesis, one of the most ideal process is catalytic dehydrative coupling reactions in which only water is produced as a waste. In this mini-review, Tsuji-Trost reaction of allyl alcohol with carbonyl compounds are described briefly as a representative process. Especially, Ni-catalyzed process employing aldehyde as a carbon pronucleophile recently developed by Sauthier et al. is introduced in detail. Their reaction do not require activator such as acid or base. The reaction condition they developed is also applicable for construction of a quaternary stereocenter with α, β-unsaturated aldehydes.

Important raw materials in fluoro chemical industry such as hydrogen fluoride, fluorine gas, fluoro monomers have been widely used as a fluorine source or a fluorinated building block. Some typical examples of fluorination reactions with these raw materials and the related recent advances are briefly introduced.