Zen-ichi Yoshida

Electronic spectra of mono-substituted anthraquinones and solvent effects

Abstract A systematic investigation of the near UV and visible spectra of mono-substituted anthraquinones and the solvent effects on the longest wavelength π → π* absorption band of these compounds reveals that the longest wavelength π → π* band of 1- and 2-substituted anthraquinones with electron donating groups can be assigned to the intramolecular electron transfer transition from the substituents to the anthraquinone nucleus. The effect of the intramolecular hydrogen-bonding between the carbonyl group of the quinone and the adjacent substituents on the π → π* absorption band has also been investigated. The absorption frequency-shifts in various solvents indicate that the value of the frequency-shift mainly depends on the strength of the hydrogen bond between the substituents and the solvent molecules. The largest shifts are caused by the interaction between active hydrogen of the substituents and the proton accepting solvents. In the case of 1-substituted anthraquinones, however, the intramolecular hydrogen-bonding is favoured and the solvent shifts are small. In the absence of the intermolecular hydrogen bonds, the solvent shifts are well interpreted by McRaes equation.

Generation of 2-Carboethoxyethylzinc iodide and 3-carboethoxypropylzinc iodide and their application to the synthesis of γ- and δ-keto esters

Abstract 2-Carboethoxyethylzinc iodide and 3-carboethoxypropylzinc iodide are generated by the reaction of the corresponding iodoesters with Zn-Cu couple and utilized for the palladium catalyzed coupling reaction with acid chloride to quantitatively provide gamma- and delta- keto esters, respectively.

How the π Conjugation Length Affects the Fluorescence Emission Efficiency

How the pi conjugation length affects the fluorescence emission efficiency is elucidated by examination of the theoretical and experimental relationship between absolute quantum yield (Phi(f)) and magnitude (Api) of the pi conjugation length in the excited singlet state, which provides a novel concept for molecular design for highly fluorescent organic compounds. As a tool to predict Phi(f) from a structural model, (nu(a) - nu(f))1/2 x a3/2 (nu(a): wavenumber of absorption maximum, nu(f): wavenumber of emission maximum, a: molecular radius) could be used instead of Api. The concept should be valuable for potential applications to (1) examination of an excited singlet state structure (for example, coplanarity of excited-state molecules) and (2) molecular design of novel materials, in which the excited singlet state plays an important role, such as highly efficient fluorophores, electroluminescent materials, photoconducting materials, and nonlinear optical materials. A remarkably intense green fluorophore (Phi(f) 0.88, log epsilon 4.72, lambda(em) 527 nm) is created based on this concept, which is of great interest in relation to a green fluorescent protein (Topaz, T203Y type, Phi(f) 0.60, log epsilon 4.98, lambda(em) 527 nm).

New molecular energy storage systems

Abstract In order to find an outstanding molecular energy storage system A/B composed of a cycle of reactions including a direct sunlight-induced endoergic process and an energy-releasing reverse process, the photochemical valence isomerization of new organic compounds leading to highly strained systems was investigated on the basis of new concepts. Metal complex catalysis for the energy-releasing process was also studied using homogeneous and heterogeneous catalysts. Consequently we found an excellent system (“DONAC”). A bench-scale test plant was constructed to examine the practical application of the energy-releasing process from donor-acceptor quadricyclane to donor-acceptor norbornadiene.

Synthesis and properties of ethanediylidene-2,2′-bis(1,3-dithiole)

Abstract A new type of electron donors in the charge-transfer complex formation, ethanediylidene-2,2′-bis(1,3-dithiole)′s, have been synthesized by the reaction of (1,3-dithiolidene)phosphoranes with 2-formylmethylene-1,3-dithioles and their properties have been discussed.

Palladium catalyzed oxycarbonylation of 4-penten-1,3-diols: efficient stereoselective synthesis of cis 3-hydroxytetrahydrofuran 2-acetic acid lactones

Abstract cis 3-Hydroxytetrahydrofuran acetic acid lactones have been prepared selectively and in high yield by an intramolecular palladium catalyzed oxycarbonylation of 4-penten-1,3-diols under mild conditions (room temperature, 1 atm of CO).

A convenient and efficient unsymmetrical ketone synthesis from acid chlorides and alkyl iodides catalyzed by palladium

Abstract Unsymmetrical ketones are prepared in good or excellent yields by a palladium catalysed coupling reaction of acid chlorides and alkyl iodides mediated by Zn-Cu couple.

Unsymmetrical ketone synthesis via palladium catalyzed carbonylation of organic halides

Abstract Aryl alkyl (or benzyl) ketones are selectively prepared by the reaction of aryl iodides and alkyl iodides (or benzyl chlorides) in the presence of a stoichiometric amount of zinc-copper couple and a catalytic amount of palladium(0) complex under an atmospheric pressure of carbon monoxide.

Intramolecular hydrogen bond in enol form of 3-substituted-2,4-pentanedione

Abstract The 3-substituent effect on the enolic ring of 2,4-pentanedione has been investigated. A linear relationship between the chemical shifts of the enolic proton and the chelated carbonyl stretching vibrations has been found for the various highly enolized 3-substituted-2,4-pentanediones. The stronger electron-withdrawing resonance effect of the substituent at 3-position results in the lower magnetic field shift of the enolic proton and the lower frequency shift of the chelated carbonyl stretching. Semi-empirical Huckel calculations have been performed to enable discussion of the electronic effect of the substituents.

Stereoselective Intramolecular Aminocarbonylation of 3-Hydroxypent-4-enylamides Catalyzed by Palladium

Abstract The urethanes and tosamides of 3-Hydroxypent-4-enylamine and its C1  C4 substituted derivatives undergo the palladium catalyzed intramolecular aminocarbonylation (0.1 equiv of PdCl2, 3.0 equiv of CuCl2, 3.0 equiv of NaOAc in acetic acid under ca. 1 atm of CO) to give selectively cis 3-hydroxypyrrolidine 2-acetic acid lactone and its C2  C5 substituted derivatives in good yields (66 – 90%), respectively.