Synthesis of 3-[[(2-benzimidazolyl)thio]methyl]-1-methyl-1,8-dihydrocycloheptapyrazol-8-ones

3-(Bromoacetyl)tropolone was reacted with five 2-mercaptobenzimidazoles to give 3-[[(2-benzimidazolyl)thio]acetyl]tropolones. These products were heated with methylhydrazine to afford 3-[[(2-benzimidazolyl)thio]methyl]-1-methyl-1,8-dihydrocycloheptapyrazol-8-ones. In these reactions, 1-methyl-3-[(1-methylhydrazino)methyl]-1,8-dihydrocycloheptapyrazol-8-one was isolated as a minor product.     

Exclusive formation of alpha-methyleneoxetanes in ketene-alkene cycloadditions. Evidence for intervention of both an alpha-methyleneoxetane and the subsequent 1,4-zwitterion

This paper describes a new mechanistic feature for the Staudinger ketene-alkene cycloaddition reactions to give cyclobutanones. Low-temperature NMR (13C, 19F, and 1H) monitoring of a reaction between bis(trifluoromethyl)ketene (1) and ethyl vinyl ether (2) has shown that the Staudinger reaction proceeds to form initially and exclusively an alpha-methyleneoxetane (3) by [2 + 2](C=O) cycloaddition across the ketene C=O bond. The initial intermediate 3 undergoes ring cleavage to produce a 1,4-zwitterion (4), which is converted to the final [2 + 2](C=C)-type product, cyclobutanone (5). The key intermediate 3 has been isolated in its pure form and was found to be converted to the final products 5 on warming, via the 1,4-zwitterion 4. The alpha-methyleneoxetane 3 is so reactive that it reacts with methanol rapidly even at -80 degrees C via solvolysis to afford an adduct 7. The ion 4 derived from the pure isolated oxetane 3 was intercepted with acetone by a 1,4-dipolar cycloaddition to give a 1,3-dioxane 8. An open-chain alpha,beta-enone (6) has been also obtained from 3. We conclude that the (1 + 2) reaction proceeds in a new three-step mechanism; formation of an alpha-methyleneoxetane 3, a [2 + 2]-type cycloadduct across the C=O bond of ketene, followed by ring cleavage to give the zwitterion 4 and by recombination to form the final product, cyclobutanone 5. The zwitterion 4 is not equilibrating with reactants 1 and 2 but comes from the alpha-methyleneoxetane 3. Exclusive formation of another oxetane 12 has been observed in a reaction between diphenylketene (9) and methyl isopropenyl ether (11). The selectivity of initial formation of cyclobutanone or oxetane has been generalized with aid of frontier-orbital theory and ab initio calculations.     

Hydrolytic polycondensation of vinyltrimethoxysilane and formation of vinylpolysiloxane films

Hydrolytic polycondensation of vinyltrimethoxysilane (VTM) was investigated in detail to prepare vinylpolysiloxanes (VPS) having spinnability and tough gel films. VTM was hydrolyzed in various molar ratios r₁ (H₂O/VTM) = 0.5–1.6 (HCl/VTM = 0.105, EtOH/VTM = 1.44) at 70°C under a N₂ stream with stirring at 150 rpm to give vinylpolysiloxanes with =510–2100 ( =1.1–10.4). The controlled hydrolysis in r₁ = 1.40–1.64 formed VPSs having the various degrees of spinnability at N₂ flow rates of 100–500 ml/min. Transparent films of thickness 0.1–0.05 mm and tensile strength 5–16 MPa were prepared when a 20 wt% acetonemethanol (1:1, V/V) solution of VPS (r₁=1.64) was cast at 80°C for several ten days. The reaction was followed by ²⁹Si-NMR spectroscopy to investigate the distribution of unit structures T¹, T² and T³ in VPS depending on r₁.     

Electronic structures of five-coordinate iron(III) porphyrin complexes with highly ruffled porphyrin ring

The spin states of the iron(III) complexes with a highly ruffled porphyrin ring, [Fe(TEtPrP)X] where X = F-, Cl-, Br-, I-, and ClO4(-), have been examined by 1H NMR, 13C NMR, EPR, and M?ssbauer spectroscopy. While the F-, Cl-, and Br- complexes adopt a high-spin (S = 5/2) state, the I- complex exhibits an admixed intermediate-spin (S = 5/2, 3/2) state in CD2Cl2 solution. The I- complex shows, however, a quite pure high-spin state in toluene solution as well as in the solid. The results contrast those of highly saddled [Fe(OETPP)X] where the I- complex exhibits an essentially pure intermediate-spin state both in solution and in the solid. In contrast to the halide-ligated complexes, the ClO4(-) complex shows a quite pure intermediate-spin state. The 13C NMR spectra of [Fe(TEtPrP)ClO4] are characterized by the downfield and upfield shifts of the meso and pyrrole-alpha carbon signals, respectively: delta(meso) = +342 and delta(alpha-py) = -287 ppm at 298 K. The data indicate that the meso carbon atoms of [Fe(TEtPrP)ClO4] have considerable amounts of positive spin, which in turn indicate that the iron has an unpaired electron in the d(xy) orbital; the unpaired electron in the d(xy) orbital is delocalized to the meso positions due to the iron(d(xy))-porphyrin(a(2u)) interaction. Similar results have been obtained in analogous [Fe(TiPrP)X] though the intermediate-spin character of [Fe(TiPrP)X] is much larger than that of the corresponding [Fe(TEtPrP)X]. On the basis of these results, we have concluded that the highly ruffled intermediate-spin complexes such as [Fe(TEtPrP)ClO4] and [Fe(TiPrP)ClO4] adopt a novel (d(xz), d(yz))3(d(xy))1(d(z)(2)1 electron configuration; the electron configuration of the intermediate-spin complexes reported previously is believed to be (d(xy))2(d(xz)), d(yz))2(d(z)(2))1.     

Chemical shift of meso-carbon: a powerful probe to determine the coordination structure and electron configuration of ferric porphyrin complexes

The meso-13C chemical shifts have been revealed to serve a powerful probe to determine the coordination structure and electron configuration of ferric porphyrin complexes.     

Synthesis and functionalization of 3,3'-bis(spirodienone)-bridged 2,2'-bithiophene: a new building block for redox-active molecular switching materials

Bithiophene derivatives bridged with a bis(spirodienone) unit were synthesized and characterized. Lithiation of the thiophene rings of an unsubstituted derivative proceeded without decomposition of the bis(spirodienone) skeleton. Palladium-catalyzed cross-coupling reactions (Suzuki-Miyaura, Sonogashira) with bromides afforded a variety of pi-extended derivatives. Bond breaking and formation under redox conditions were observed by cyclic voltammetry.     

Thermoresponsive characteristics of fluoroalkyl end-capped co-oligomers in aqueous solutions and on the poly(methyl methacrylate) film surface

Fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide--acryloylmorpholine co-oligomers were prepared by the co-oligomerizations of fluoroalkanoyl peroxides with the corresponding monomers. These fluorinated co-oligomers exhibited a lower critical solution temperature (LCST) characteristic in aqueous solutions. Of particular interest, a steep time dependence of contact angle values for dodecane was observed from 40 to 60 degrees C to decrease their values, effectively, on the modified PMMA [poly(methyl methacrylate)] film surface treated with fluorinated co-oligomer possessing the LCST: 36 degrees C (in water), although such a steep time dependence was not observed from 20 to 30 degrees C.     

Study on chemical speciation in aluminum chloride solution by ESI-Q-MS

AlCl(3) solution was analyzed at concentrations from 0.02 to 100 mM using an electrospray ionization quadrupole mass spectrometer (ESI-Q-MS), and the dissolution state of aluminum ions is discussed. Results obtained using ESI-Q-MS were consistent with those obtained using (27)Al nuclear magnetic resonance ((27)Al NMR). Aluminum species existed mainly as positively charged monomeric aluminum hydroxide coordinated with several water molecules in solution. The complexation of chloride ions by aluminum ions differed between the positive and negative ion modes. Chemical reactions that partially modified chemical forms of species through ESI-Q-MS measurement were also observed. In the same aluminum chloride solution, using ESI-TOF-MS and ESI-Q-MS/MS studies, the disagreement of the reports is discussed. It is concluded that ESI-TOF-MS might show also the gas-phase reaction in the mass spectrometer but the dissolution state of aluminum species can be shown by ESI-Q-MS.     

Preparation of novel fluoroalkyl end-capped oligomeric nanoparticles-encapsulated hibitane

Fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomer [R_F-(DOBAA)_n-R_F] reacted with hibitane in methanol at 90 °C to afford R_F-(DOBAA)_n-R_F oligomeric nanoparticles-encapsulated hibitane in good isolated yields. These fluorinated oligomeric particles-encapsulated hibitane were nanometer size-controlled very fine particles, and were found to exhibit a good dispersibility and stability in a wide variety of traditional organic solvents including fluorinated aliphatic solvents. Each dispersed solution with fluorinated nanoparticles afforded transparent colorless solution. These fluorinated nanoparticles were also found to exhibit a good antibacterial activity, and were applied to the surface modification of traditional organic polymers such as poly(methyl methacrylate).     

Rearranged lanostane triterpenoids from Abies sachalinensis (III)

To isolate more rearranged lanostane-type triterpenes from Abies sachalinensis, continuous chemical investigation of the ethyl acetate soluble fraction of the methanol extract of A. sachalinensis afforded two new rearranged lanostane-type triterpenes (1, 2). Their structures were elucidated to be 3,4-seco-4(28),7,12,24-mariesatetraen-26,23-olide-23-hydroxy-3-oic acid (1) and ethyl 3,4-seco-8(14-->13R)abeo-17,13-friedo-4(28),7,14,24-lanostatetraen-26,23-olide-23-hydroxy-3-oate (2), respectively. The structure of these compounds was determined by spectral studies, especially by two-dimensional (2D)-NMR and high-resolution (HR)-MS. Compounds 1 and 2 have a tautomeric lactone structure in the side chain.