Shigeyasu Kuroda

Au(I)-Catalyzed Cycloisomerizations Terminated by sp3 C-H Bond Insertion

The gold(I)-catalyzed cycloisomerization of 1,5-enynes and 1,4-allylallenes to tetracyclododecane and tetracyclotridecane derivatives, respectively, is reported. Complexation of the cationic gold(I) complex to either the alkyne or allene moiety induces an intramolecular addition of the alkene, leading to a gold(I)-stabilized carbenoid intermediate. This intermediate undergoes a formal sp(3) C-H insertion to generate the tetracyclic adduct. A series of deuterium labeling experiments showed that the C-H functionalization step proceeds with an inverse kinetic isotope effect.

Comparative assessment of the efficiency of Fe-doped TiO2 prepared by two doping methods and photocatalytic degradation of phenol in domestic water suspensions

Abstract Fe-doped TiO2 particles responding to visible light were synthesized by impregnation and calcination method using TiO2 particle and Ti element, respectively. The optical and the chemical properties were characterized by measuring the X-ray diffraction (XRD) and UV–visible spectroscopy. The onset of absorption shifted to longer wavelengths on doping TiO2 by the calcination process, which showed a better response as compared to the impregnation method. The photocatalytic reactivity was evaluated by the degradation of phenol with impregnated Fe-doped (0.5% w/w in Fe) and calcined Fe-doped (FexTi1 xO2, x ¼ 0.005 (Fe/Ti molar ratio)) TiO2 separately in distilled and tap water. The characterization results have confirmed the advanced possibility of correlation between photoactivity and the special property of sulfur-containing calcined Fe-doped TiO2. In case of the coagulation of the undoped A-I and the Fe-doped B-I, the photoactivity showed a decrease due to the presence of natural electrolytes and due to the high pH of tap water, whereas in the case of the coagulation of calcined Fe-doped TiO2 prepared from sulfides (FexTiS2), the photoactivity showed an increase. In this study, highest catalytic activity was found to be strongly dependent both on catalyst structure and on the type of water used.

6-Amino-2,2′-bipyridine as a new fluorescent organic compound

6,6′-Diamino-2,2′-bipyridine (1a) has been found to exhibit a strong fluorescence in the near-UV region. Some amino and/or chloro substituted bipyridines (bpys) have been synthesized and studied to show that only 6-amino-substituted derivatives exhibited a strong emission. The emission of 6-amino-6′-chloro-bpy (3a) was the strongest (λmax= 429.0 nm; Φ= 0.78 in ethanol) among them. On the other hand, little or no emission was observed for monochloro-, dichloro- and 4-amino- derivatives.

Adsorption and aggregation of Fe(III)-hydroxy complexes during the photodegradation of phenol using the iron-added-TiO2 combined system.

The behavior of Fe(III) aquacomplexes in TiO(2) suspensions in the degradation of phenol has been investigated. The most active Fe(OH)(2+) species adsorbed on the surface of TiO(2) retards the conversion of Fe(OH)(2+) into oligomers and therefore increases the percentage of Fe(OH)(2+) with irradiation time, with a consequent enhancement in the catalytic cycle of Fe(III)/Fe(II) and excited charge traps by Fe(III) in the iron-TiO(2) system. The influence of iron addition on TiO(2) was obtained when the regeneration of [Fe(OH)(2+)] remained continuous with irradiation time. In an optimum TiO(2) suspension (0.5g/L) with the addition of 0.1mM Fe(III), the measured k(obs) values for phenol degradation were enhanced for the higher adsorption of Fe(OH)(2+) on the reactive surface of TiO(2) at a specified irradiation time.

Synthesis, Stability, and X-Ray Crystallographic Structure Analysis of Spiro[1H-azulenium-1,1′-cycloalkane] Ions

Abstract Direct cycloalkylation of 1,6-dihydroazulene and subsequent hydride abstraction with a trityl salt gave spiro[1H-azulenium-1,1′-cyclopentane and -1,1′-cyclohexane] ions (3 and 4). On the other hand, spiro[1H-azulenium-1,1′-cycloheptane] ion (5) was synthesized from 1-acetylcyclohepta-1,3,5-triene by a sequence involving the Mukaiyama aldol reaction, the Nazarov cyclization, the Shapiro reaction, and hydride abstraction. These cations showed greater kinetic stability than the three- and four-membered ring homologues. Their pKR+ values are far greater compared with those of the known disubstituted tropylium cations and are in the order of the number of carbon atoms at the 1 position, indicating that an inductive effect of the spiroalkyl groups, besides the π-conjugative and σ-conjugative effects, governs the thermodynamic stability. X-Ray crystallographic structure analysis of these cations was also described.

The synthesis of methano-bridged bisdehydro [18]-, -[20]-, -[22]-, and -[24] annulenes

Abstract Title annulenes were synthesized by Wittig reaction of cyclohepta-1,3,5-triene-1,6-dialdehyde or its vinylogous dialdehydes with 5-methylpenten-2-yn-4-yltriphenylphosphonium bromide, followed by intramolecular oxidative couplings of the resulting acyclic compounds, and they proved to be diatropic or paratropic, corresponding to the number of peripheral π-electrons.

Synthesis and properties of azuleno[2,1-a]-3-8-methano[ 10 ] annulene and its 2-methyl derivative

The cata-condensed system if azulene fused with 1,6-methano [ 10 ]annulenes was synthesized. The 1H NMR spectra revealed the existence of diastropicity as 18-pi electron periphery.

Generation and [4+2] cycloaddition of 1,6-methano[10]annulene-3,4-quinodimethane: a novel synthesis of dimethyl 1,6-methanobenzo[3,4-a][10]annulene-13,14-dicarboxylate ☆

Abstract A new quinodimethane, 1,6-methano[10]annulene-3,4-quinodimethane ( 1 ), was generated and trapped by the Diels–Alder reactions with various dienophiles to provide 1,6-methano[10]annelenes 3 fused with a six-membered ring at the 3,4-positions, one of which was derived to a benzene ring analogue 4 .

Catalytic activities of nickel (II) complexes of a salen analog, [Ni(babp)], in epoxidation of olefins

Abstract A salen analog [Ni(babp)] (babp = 6,6′-bis (benzoylaminato)-2,2′-bipyridine (2—)) and its t -butyl derivative catalysed epoxidation of olefins in the presence of sodium hypochlorite as the oxidant. These complexes showed higher catalytic activity than [Ni (salen)] in epoxidation of an electron-deficient olefin, allyl chloride, yielding epichlorohydrin in 43% yield.

A Synthetic Method for Preparing 3,3-Dialkyl-1,2,3,8-tetrahydroazulen-1-one

Abstract The trimethylsilyl enol ether of l-acetylcyclohepta-1,3,5-triene was transformed to 3,3-dialkyl-1,2,3,8-tetrahydroazulen-1-one by a two-step sequence involving the Mukaiyama aldol reaction with ketones and the subsequent Nazarov cyclization.