Diiron amido-imido complex [(CpFe)2(mu2-NHPh)(mu2-NPh)]: synthesis and a net hydrogen atom abstraction reaction to form a bis(imido) complex

A reaction between [CpFeCl]x and LiNHPh (1 equiv to Fe) produces a new paramagnetic Fe(II)-Fe(III) mu2-amido-mu2-imido complex [(CpFe)2(mu2-NHPh)(mu2-NPh)] (1), which, upon interaction with 2,2'-azobis(2,4-dimethylvaleronitrile), undergoes a net N-H hydrogen atom abstraction reaction to give a diamagnetic Fe(III)-Fe(III) mu2-imido dimer [CpFe(mu2-NPh)]2 (2). The molecular structures of 1 and 2 have been determined by single-crystal X-ray diffraction.     

Nickel-catalyzed [3+1+1] cycloaddition reactions of alkenyl Fischer carbene complexes with methylenecyclopropanes

Methylenecyclopentanones were synthesized by the nickel-catalyzed [3+1+1] cycloaddition reactions of alkenyl Fischer carbene complexes with methylenecyclopropanes. The methylenecyclopropane was transformed into the C(2)-symmetric bis-cyclopentapyridazine derivative by reacting with p-toluenesulfonyl hydrazine.     

Biodegradable Polyurethanes from Plant Components

Abstract

Polyurethane (PU) sheets and foams having plant components in their network were prepared by using the following procedure. Polyethylene glycol (PEG) was mixed with one of the following; molasses, lignin, woodmeal, or coffee grounds. The mixture obtained was reacted with diphenylmethane diisocyanate (MDI) at room temperature, and precured PUs were prepared. The precured PUs were heat-pressed and PU sheets were obtained. In order to make PU foam, the above mixture was reacted with MDI after the addition of plasticizer, surfactant (silicone oil), catalyst (di-n-butyltin dilaurate), and droplets of water under vigorous stirring. The glass transition temperature, tensile and compression strengths, and Young's modulus of the PU sheets and foams increased with an increasing amount of plant components. This suggests that saccharide and lignin residues act as hard segments in PUs. It was found that the PUs obtained were biodegradable in soil. The rate of biodegradation of the PUs derived from molasses and coffee grounds was between that of cryptomeria (Cryptomeria japonica) and beech (Fagus sieboldi).     

Fully automated liquid chromatography-mass spectrometry determination of 17beta-estradiol in river water

Surface modified molecularly imprinted polymers (SM-MIPs) for 17beta-estradiol (E2), utilizing 6-ketoecradiol as a pseudo template were prepared. MIPs for E2 were synthesized using 4-vinyl pyridine and ethylene dimethacrylate as a functional monomer and cross-linking agent, respectively. MIPs selectively retained E2 and provided excellent chromatographic resolution from interfering compounds inherent in river water sample matrices. Therefore, freshly prepared MIPs were applied to quantitative mass spectrometric (negative electrospray ionization mode) detection of low levels of E2 in river water sample. In order to pre-concentrate the target compound for HPLC analysis, column switching was coupled with a pretreatment column packed with the MIPs. The repeatability of actual determinations of river water sample, in which background E2 was not detected, spiked with 50 ng/L of E2 was 2.2% RSD with a detection limit and qualification limit of 1.8 and 5.4 ng/L, respectively. Surface modification of MIP particlefs packed in the pretreatment column provided selective affinity and on-line concentration of low levels of E2 while simultaneously eliminating sample matrix interference, resulting in a significant increase in sensitivity and reproducibility for liquid chromatography-mass spectrometry analysis of E2 in river water sample.     

Theoretical study of pyrazolate-bridged dinuclear platinum(II) complexes: interesting potential energy curve of the lowest energy triplet excited state and phosphorescence spectra

Four kinds of 3,5-dialkylpyrazolate(R2pz)-bridged dinuclear platinum(II) complexes [Pt2(mu-R2pz)2(dfppy)2] (dfppy=2-(2,4-difluorophenyl)pyridine; R2pz=pyrazolate in 1, 3,5-dimethylpyrazolate in 2, 3-methyl-5- tert-butylpyrazolate in 3, and 3,5-bis(tert-butyl)pyrazolate in 4) were theoretically investigated by the DFT(B3PW91) method. The Stokes shift of their phosphorescence spectra was discussed on the basis of the potential energy curve (PEC) of the lowest energy triplet excited state (T1). This PEC significantly depends on the bulkiness of substituents on pz. In 1 and 2, bearing small substituents on pz, one local minimum is present in the T1 state besides a global minimum. The local minimum geometry is similar to the S0-equilibrium one. The T1 state at this local minimum is characterized as the pi-pi* excited state in dfppy, where the dpi orbital of Pt participates in this excited state through an antibonding interaction with the pi orbital of dfppy; in other words, this triplet excited state is assigned as the mixture of the ligand-centered pi-pi* excited and metal-to-ligand charge transfer excited state ((3)LC/MLCT). The geometry of the T1-global minimum is considerably different from the S0-equilibrium one. The T1 state at the global minimum is characterized as the triplet metal-metal-to-ligand charge transfer ((3)MMLCT) excited state, which is formed by the one-electron excitation from the dsigma-dsigma antibonding orbital to the pi* orbital of dfppy. Because of the presence of the local minimum, the geometry change in the T1 state is suppressed in polystyrene at room temperature (RT) and frozen 2-methyltetrahydrofuran (2-MeTHF) at 77 K. As a result, the energy of phosphorescence is almost the same in these solvents. In fluid 2-MeTHF at RT, on the other hand, the geometry of the T1 state easily reaches the T1-global minimum. Because the T1-global minimum geometry is considerably different from the S0-equilibrium one, the phosphorescence occurs at considerably low energy. These are the reasons why the Stokes shift is very large in fluid 2-MeTHF but small in polystyrene and frozen 2-MeTHF. In 3 and 4, bearing bulky tert-butyl substituents on pz, only the T1-global minimum is present but the local minimum is not. The electronic structure of this T1-global minimum is assigned as the (3)MMLCT excited state like 1 and 2. Though frozen 2-MeTHF suppresses the geometry change of 3 and 4 in the T1 state, their geometries moderately change in polystyrene because of the absence of the T1-local minimum. As a result, the energy of phosphorescence is moderately lower in polystyrene than in frozen 2-MeTHF. The T1-global minimum geometry is much different from the S0-equilibrium one in 3 but moderately different in 4, which is interpreted in terms of the symmetries of these complexes and the steric repulsion between the tert-butyl group on pz and dfppy. Thus, the energy of phosphorescence of 3 is much lower in fluid 2-MeTHF than in frozen 2-MeTHF like 1 and 2 but that of 4 is moderately lower; in other words, the Stokes shift in fluid 2-MeTHF is small only in 4.     

Synthesis and structure-activity relationship study of monotesone-A, an antifungal component of Monotes engleri

The synthesis of (+/-)-monotesone-A, an antifungal component of Monotes engleri, as well as its four structural analogues were accomplished starting from the corresponding MOM-protected phloracetophenone and benzaldehyde derivatives. Antifungal activities of the five flavanone derivatives were studied against Candida albicans (14053 and ATCC 10231), Candida inconspicua, Candida dubliniensis and Candida krusei.     

A mild inter- and intramolecular amination of aryl halides with a combination of CuI and CsOAc

A unique combination of CuI and CsOAc was found to catalyze aryl amination under mild conditions. The reaction takes place at room temperature or at 90 °C with broad functional group compatibility. The intramolecular reaction was able to form five-, six-, and seven-membered rings with various protecting groups on the nitrogen atom. The scope of the intermolecular amination, as well as its applications to unsymmetrical N,N′-dialkylated phenylenediamines, was investigated.     

Enantioselective synthesis of phomallenic acid C, an inhibitor of FAS II pathway

Enantioselective synthesis of phomallenic acid C, an inhibitor of bacterial FAS II pathway, was successful. Allenyldiyne structure was constructed by a direct anti-S_N2′ coupling of propargyl mesylate with diynylindium in the presence of palladium catalyst. Enantiomeric purity was determined by Ohrui-Akasaka method to be 83%ee.     

Inclusion polymerization of 1-chlorobutadiene in a deoxycholic acid canal

Inclusion polymerization of 1-chlorobutadiene was studied using 3α,12α-dihydroxy-5β-cholan-24-oic acid (deoxycholic acid, DCA) as host molecules. It was found that the poly(1-chlorobutadiene) had almost 100% of head to tail, trans-1,4-structure on the basis of ¹³C-NMR and IR spectroscopies. This was the first example of preparing the highly regulated poly(1-chlorobutadiene) by using the inclusion polymerization technique. The polymers obtained were optically active and the maximum value of specific rotation was [α]_D-41.9°. Both the rate constants and the value of activation energy of the elementary reactions of inclusion polymerization of 1-chlorobutadiene were determined by graphical evaluation. The activation energy of propagation and termination was 11.7 and 11.1 kcal/mol, respectively.     

Galloyl-Derived Orthoquinones as Reactive Partners in Nucleophilic Additions and Diels-Alder Dimerizations: A Novel Route to the Dehydrodigalloyl Linker Unit of Agrimoniin-Type Ellagitannins

Orthochloranil-mediated oxidation of galloyl monoethers furnishes the derived orthoquinones in excellent yield. These reactive electrophiles participate in a variety of nucleophilic addition reactions with heteroatomic and carbanionic partners. In addition, Lewis acid-mediated dimerization of the orthoquinones provides an efficient route to dehydrodigalloyl-type diaryl ether units characteristic of several ellagitannin natural products. The implications for ellagitannin biosynthesis and gallotannin-protein covalent attachment are discussed.