Takamichi Yamagishi

A new tripodal anion receptor with CH···X− hydrogen bonding

1,3,5-{Tris(3-n-butylimidazolio)methyl}-2,4,6-trimethybenzene 1, which has three imidazolium groups connected through a 1,3,5-trimethylbenzene spacer, has been synthesized as a novel receptor for halide anions. This tripodal receptor is shown to bind strongly Cl−, Br−, and I− anions in CD3CN through electrostatic interactions and CH···X− hydrogen bonds.

Palladium-catalyzed asymmetric alkylation via π-allyl intermediate: Acetamidomalonate ester as a nucleophile.

Abstract Asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with sodium salt of acetamidomalonate ester has been carried out in the presence of a palladium catalyst containing ( S )-BINAP to give a chiral α-allyl-αacetamidomalonate ester derivative of high optical purity (94±1% ee).

Palladium-catalyzed asymmetric allylic alkylation using dimethyl malonate and its derivatives as nucleophile

Abstract Palladlum-catalyzed asymmetric allylic alkylatlon of 1,3-dlphenyl-2-propenyl acetate with sodium salt of dimethyl malonate and its derivatives has been successfully carried out in the presence of optically active diphosphine, such as (S)-BINAP. High enantioselectivity of up to 90% ee was obtained with dimethyl malonate.

Mechanism of silver(I)-catalyzed Mukaiyama aldol reaction: active species in solution in AgPF 6 -(S)-BINAP versus AgOAc-(S)-BINAP systems

Abstract Silver(I)-diphosphine complex is an effective catalyst for Mukaiyama Aldol reaction in polar solvents. AgPF6-(S)-BINAP cationic chiral complex indicated a good activity and could afford fairly high enantioselectivity in the reaction of aromatic aldehydes and silyl enol ethers. On the other hand, AgOAc-(S)-BINAP system afforded the aldol product of the absolute configuration opposite to that by AgPF6-(S)-BINAP and very high catalytic activity was shown. The structure and equilibrium state of Ag(I)-BINAP complexes in solution were examined to understand the reaction mechanism. In AgPF6 system [Ag((S)-BINAP)2]PF6 (1a), [Ag((S)-BINAP)]PF6 (1b), [Ag2((S)-BINAP)](PF6)2 (1c) and AgPF6 are present in solution. The active species of the aldol reaction in DMF is [Ag((S)-BINAP)]PF6 (1b), which exists as a minor species in solution. For this cationic Ag(I) catalyst, cyclic transition state containing substrate and silyl enol ether is assumed. In AgOAc-(S)-BINAP system, active species is also monomeric AgOAc((S)-BINAP) (2b) species which exists as a major component in solution and strong interaction was observed with a silyl enol ether. The reaction by AgOAc-(S)-BINAP catalyst is concluded to proceed as follows: nucleophile forms a complex with AgOAc-(S)-BINAP species and is activated. This complex attacks aldehydes to afford aldol adduct via acyclic transition state.

Effective transfer hydrogenation of unsaturated compounds by ruthenium dihydride complex in propan-2-ol

Abstract Ruthenium(II)-hydride complexes were very effective catalysts for the transfer hydrogenation of ketones and imines using propan-2-ol as hydrogen donor in the presence of a base. By using the catalyst dihydridotetrakis(triphenylphosphine)-ruthenium(II), the reduction proceeded effectively in the absence of a base. This ruthenium dihydride catalyst also caused the transfer hydrogenation of benzonitrile to afford benzylamine derivatives albeit in a moderate yield. Isotope labeling experiments in the reaction of N-(2-naphthylmethylidene)benzylamine with this ruthenium dihydride catalyst revealed the hydride transfer from ruthenium hydride to the C N bond of the substrate. In the case of the ruthenium monohydride species, no transfer hydrogenation occurred for ketones, imines and nitrile in the absence of a base except at the C C double bond of conjugated carbonyl compounds.

A novel chiral phosphinediamine ligand and asymmetric hydrogenation of acrylic acid derivatives

Abstract A novel chiral phosphinediamine ligand (PN 2 ) was prepared from ( S )-1-phenylethylamine and dichloroisopropylphosphine. The rhodium-PN 2 catalyst utilizing selective ligation of the amino unit and electrostatic interaction between the ligand and a substrate gave high enantioselectivities up to 92% ee in asymmetric hydrogenations of acrylic acid derivatives.

Asymmetric transfer hydrogenation of aryl-alkyl ketones catalyzed by ruthenium(II) complexes having chiral pyridylmethylamine and phosphine ligands

Abstract In the asymmetric transfer hydrogenation of aromatic ketones using propan-2-ol or a formic acid–triethylamine mixture as hydrogen donor, a mixed ligand ruthenium(II) complex generated in situ from pyridylmethylamine ligands and RuCl2(PPh3)3 or RuHCl(PPh3)3 were examined. In propan-2-ol, the direction of the chirality induction was very sensitive to the aryl substituent of chiral amino unit in pyridylmethylamine ligands. Using HCOOH/NEt3 as hydrogen donor, catalytic activities and enantioselectivities were much improved (up to 100% conversion and 86% e.e.) with ruthenium complex generated from RuHCl(PPh3)3 and 2-pyridylmethyl-1-(R)-phenylethylamine.

Syntheses of mixed-ligand ruthenium(II) complexes with a terpyridine or a tris (pyrazolyl) methane and a bidentate ligand: their application for catalytic hydroxylation of alkanes

Abstract The new mixed-ligand chlororuthenium(II) complexes [RuCl(L) (tpy)]Cln and [RuCl(L) (tpm)]Cln(L = bpy, dmpa or dmgly; n = 0 or 1) were prepared, and the catalytic activity for alkane oxidation using m-chloroperbenzoic acid was examined. Alcohol was the main product: oxidation of adamantane, cyclooctane or ethylbenzene gave hydroxylated products, 1-adamantanol (66%), cyclooctanol (22%) or 1-phenylethanol (48%), respectively.

The structure determination of leucoanthraquinones by proton and carbon-13 nuclear magnetic resonance spectroscopy

Abstract Leucoquinizarin reacts with amines to give mono- and diaminoanthraquinones. Since contamination by diaminoanthraquinones greatly influences the quality of monoaminoanthraquinones as dyestuffs (and vice versa), it is important to elucidate the structure of leucoanthraquinones in connection with the reactivity and selectivity of the reaction with amines. The structure of the leuco compound of 1,4 -bis(butylamino)anthraquinone was assigned to be 1,4 -dibutylamino- 2,3 -dihydroanthracene- 9,10 -dione by p.m.r. However, the structure of the leuco compounds of 1,4 -dihydroxyanthraquinone(quinizarin) and 1 -butylamino- 4 -hydroxyanthraquinone could not be determined definitely by p.m.r. alone. An examination of 13 C-n.m.r. spectra of anthraquinones and leucoanthraquinones afforded convincing data. The structures of the leuco compounds of quinizarin and 1 -butylamino- 4 -hydroxyanthraquinone were concluded to be 9,10 -dihydroxy- 2,3 -dihydroanthracene- 1,4 -dione and 1 -butylamino- 10 -hydroxy- 2,3 -dihydroanthracene- 4,9 -dione respectively. The reactive species of leucoquinizarin are discussed on the basis of the results.

Solvatochromism of stilbazolium merocyanine-type dyes containing a benzoquinolizinium ring

Abstract The UV/VIS spectra of a series of stilbazolium merocyanine-type dyes containing a benzoquinolizinium ring have been recorded in seven solvents. The dyes with a hydroxyl group showed hypsochromic shifts (less than 50 nm) on changing the solvent from 3-methylbutan-1-ol to water. On the other hand, the azonia betaine-type dyes formed by deprotonation of the hydroxy-substituted dyes exhibited a large hypsochromic shift (about 200 nm) as the solvent polarity increased. The transition energies (ET) of the dyes having a hydroxyl group did not correlate well with solvent polarity scales such as Brookers χR and χB, Kosowers Z, and Dimroth and Reichardts ET(30), while good correlations were observed between ET of the azonia betaine-type dyes and the scales χB, Z, and ET(30). The solvatochromism was analyzed by the linear solvation energy relationship with the multi-parameter proposed by the Kamlet, Abboud, and Taft group and showed excellent correlations for the azonia betaine-type dyes. The inherent wave-number (ν0) and the susceptibility of the absorption maximum (νmax) to solvent polarity-polarizability ( π ∗ ), to solvent hydrogen-bond donating acidity (α), and to solvent hydrogen-bond accepting basicity (β) are discussed.