Shun-Ichi Murahashi

Ruthenium catalyzed biomimetic oxidation in organic synthesis inspired by cytochrome P-450

Simulation of the function of cytochrome P-450 with low valent ruthenium complex catalysts leads to the discovery of biomimetic, catalytic oxidation of various substrates selectively under mild conditions. The reactions discussed in this tutorial review are simple, clean, and practical. The principle of these reactions is fundamental and gives wide-scope and environmentally benign future practical methods.

Ruthenium-catalyzed oxidative cyanation of tertiary amines with molecular oxygen or hydrogen peroxide and sodium cyanide: sp3 C-H bond activation and carbon-carbon bond formation.

Ruthenium-catalyzed oxidative cyanation of tertiary amines with molecular oxygen in the presence of sodium cyanide and acetic acid gives the corresponding alpha-aminonitriles, which are highly useful intermediates for organic synthesis. The reaction is the first demonstration of direct sp(3) C-H bond activation alpha to nitrogen followed by carbon-carbon bond formation under aerobic oxidation conditions. The catalytic oxidation seems to proceed by (i) alpha-C-H activation of tertiary amines by the ruthenium catalyst to give an iminium ion/ruthenium hydride intermediate, (ii) reaction with molecular oxygen to give an iminium ion/ruthenium hydroperoxide, (iii) reaction with HCN to give the alpha-aminonitrile product, H2O2, and Ru species, (iv) generation of oxoruthenium species from the reaction of Ru species with H2O2, and (v) reaction of oxoruthenium species with tertiary amines to give alpha-aminonitriles. On the basis of the last two pathways, a new type of ruthenium-catalyzed oxidative cyanation of tertiary amines with H2O2 to give alpha-aminonitriles was established. The alpha-aminonitriles thus obtained can be readily converted to alpha-amino acids, diamines, and various nitrogen-containing heterocyclic compounds.

Palladium-catalyzed cross-coupling reaction of organic halides with Grignard reagents, organolithium compounds and heteroatom nucleophiles

Abstract Since palladium-catalyzed cross-coupling reaction of vinyl and aryl halides with Grignard reagents and organolithium compounds has been found, great progress on the related palladium-catalyzed reaction, which includes the reaction with heteroatom nucleophiles, has been made.

Rhenium-Catalyzed Addition of Carbonyl Compounds to the Carbon−Nitrogen Triple Bonds of Nitriles: α-C−H Activation of Carbonyl Compounds

The ReH(7)(PPh(3))(2)-catalyzed addition of carbonyl compounds to the carbon-nitrogen bond of nitriles proceeds efficiently and selectively to give the corresponding (Z)-enamines, which are important synthetic intermediates. The key step of the reaction is the chemoselective alpha-C-H activation of carbonyl compounds induced by the alpha-heteroatom effect in the presence of nitriles.

Iridium-Catalyzed Reactions of Trifluoromethylated Compounds with Alkenes: A Csp3H Bond Activation α to the Trifluoromethyl Group

Catalytic convenience: The use of iridium or ruthenium catalysts for C(sp(3))-H bond activation has led to the addition reaction of trifluoromethylated compounds to alkenes (see scheme). This atom-economical reaction occurs under neutral reaction conditions and without the formation of undesired defluorinated by-products, even at high temperature.

Switchable C‐ and N‐Bound Isomers of Transition‐Metal Cyanocarbanions: Synthesis and Interconversions of Cyclopentadienyl Ruthenium Complexes of Phenylsulfonylacetonitrile Anions

The synthesis, structure, and dynamic behavior of bistable C- and N-bound isomers of transition-metal cyanocarbanions are described. A series of C-bound cyclopentadienyl (Cp) ruthenium phosphane complexes, [Ru{CH(CN)SO2Ph}(Cp)L1L2] (3), and their N-bound isomers, [Ru+(Cp)(NCCH(-)SO2Ph)L1L2] (4), were prepared by treating [RuCl(Cp)(PR3)2] with the sodium salt of phenylsulfonylacetonitrile and performing ligand-exchange reactions with the resulting compounds. Structural characterization by X-ray diffraction indicates that the cyanocarbanion moiety of 3 has an alpha-metalated structure, whereas that of 4 has a zwitterionic, end-on structure. Heating these complexes in aprotic solvents gives rise to irreversible linkage isomerization between C- and N-bound isomers, in which the relative thermal stabilities vary greatly depending on the steric and electronic nature of the ligands. Mechanistic studies of N-to-C isomerization revealed that the reaction proceeds irreversibly in a unimolecular manner without the formation of coordinatively unsaturated species. A metal-sliding process, which occurs over the -C-C triple chemical bond N pi-conjugated surface of the cyanocarbanion moiety, was suggested by results from kinetic studies and density functional theory (DFT) calculations. C-to-N isomerizations proceed by the above-mentioned intramolecular process, with a temperature-dependent contribution from the formation and cleavage of mu2-C,N coordination dimers [{Ru{CH(CN)SO2Ph}(Cp)(PPh3)}2] (15 and 16).

Development of biomimetic catalytic oxidation methods and non-salt methods using transition metal-based acid and base ambiphilic catalysts

This review focuses on the development of ruthenium and flavin catalysts for environmentally benign oxidation reactions based on mimicking the functions of cytochrome P-450 and flavoenzymes, and low valent transition-metal catalysts that replace conventional acids and bases. Several new concepts and new types of catalytic reactions based on these concepts are described.

Professor Dr Roger A. Sheldon—65 years on

Ilya I. Moiseev, Shun-Ichi Murahashi, Martyn Poliakoff, Ken Seddon and Vytas K. Svedas reflect on a recent symposium held in honour of Roger Sheldon, a founding father of green chemistry and of this journal.