Some aspects of nitroxide-mediated living radical polymerization of N-(p-vinylbenzyl)phthalimide

The free radical polymerization of N-(p-vinylbenzyl)phthalimide (VBP) “initiated” with the adduct of 2-benzoyloxy-1-phenylethyl and TEMPO (BS-TEMPO) or TEMPO-terminated polystyrene (PS-TEMPO) in N,N-dimethylformamide (DMF) at 125 °C was found to proceed in a living fashion, providing low-polydispersity PVBP and block copolymers of the type PS-b-PVBA, where TEMPO is 2,2,6,6-tetramethylpiperidinyl-1-oxy. Unlike TEMPO-mediated styrene polymerization, the polymerization rate slightly but distinctly depended on the adduct concentration, which was interpretable as a pre-stationary behavior. The hydrolysis of those polymers gave poly(p-aminomethylstyrene) (PAMS) and PS-b-PAMS, and further treatment of the block copolymer with hydrogen chloride provided an amphiphilic block copolymer. The polymeric amphiphile was used as an emulsifier in emulsion polymerization to produce a positively charged polymeric microsphere.     

Thermal behavior of ground mixtures of heptakis (2,6-di-O-methyl)-β-cyclodextrin and benzoic acid

Characterization of an inclusion complex prepared from amorphous ground mixtures of heptakis (2,6-di-O-methyl)--cyclodextrin (DMCD) and benzoic acid was carried out by a sealed heating method. The formation of the crystalline inclusion complex and the variation in physicochemical properties of the ground mixture were investigated as a function of heating temperature. On the basis of X-ray diffractometry and Fourier transform infrared spectroscopy, the crystallization of the ground mixture was confirmed to take place at about 135°C. The crystallization temperature was shifted to lower temperatures and the bound molar ratio of benzoic acid to DMCD increased as the mixing molar ratio of benzoic acid to DMCD was raised.Tsumura & Co., 3586 Yoshiwara, Amimachi, Inashikigun, Ibaraki 300-11, Japan.     

First catalytic asymmetric hydrophosphonylation of cyclic imines: Highly efficient enantioselective approach to a 4-thiazolidinylphosphonate via chiral titanium and lanthanoid catalysts

The catalytic and enantioselective hydrophosphonylation of a cyclic imine, namely the 3-thiazoline 1, is described. We have discovered a highly efficient enantioselective de novo approach to the pharmaceutically interesting 4-thiazolidinylphosphonate 2 using either titanium or lanthanoid chiral catalysts, which gives excellent enantiomeric purities (up to 98 %ee) and high chemical yields.     

Di-isopropyl fluorophosphate electrode based on squid nerve tissue

Di-isopropyl fluorophosphatase is contained in the giant axon of squid nerve tissue. This tissue can be coupled with a fluoride ion-selective electrode to produce an electrode selective to di-isopropyl fluorophosphate. The semilogarithmic calibration curve at pH 7.1 is linear over the range 2 × 10^?6?7 × 10^?3 M (RSD < 3% ) with a slope of about 44 mV/decade. The detection limit is 8 × 10^?6 M. The electrode lifetime (with constant response characteristics) is about 16 days.     

Synthesis of [1]rotaxane via covalent bond formation and its unique fluorescent response by energy transfer in the presence of lithium ion

Although there have been a lot of reports on the synthesis and properties of [n]rotaxanes (mainly n = 2), only a few reports on the synthesis of [1]rotaxane has been published by V?gtle's group and others (see ref 5). Generally speaking, [1]rotaxane might be expected to exhibit properties different from other rotaxanes, because the rotor and the axle in the [1]rotaxane is bound covalently and closely. We report on a novel method to make [1]rotaxanes via covalent bond formation from a macrocyclic compound. That is, we first prepared a bicyclic compound from macrocycle and then proceeded to [1]rotaxane by aminolysis. This is the first synthetic example of preparation of [1]rotaxane via covalent bond formation, not utilizing weak interactions such as hydrogen bonding, charge transfer, via metal complexation, etc. This method might provide a powerful and new tool for construction of [1]rotaxane as a new supramolecular system. In addition, we investigated energy transfer from rotor to axle using [1]rotaxane that we prepared. Energy transfer occurred perfectly from the naphthalene ring of the rotor to the anthracene ring of the axle. We found also that only lithium ion among alkali ions can drastically enhance the fluorescence intensity. This finding could be applicable to ion-sensing systems, switching devices, and so on.     

Mechanism of formation of iron(II) complexes with pentadentate ligands via C-C bond formation between trans-[Fe(2,4-bis(2-pyridylmethylimino)pentane)(MeCN)2]ClO4]2.MeCN and various nitriles

The order of relative reactivity of nitriles for the formation of Fe(II) complexes (2s) with 3-(1-alkyl(or aryl)methyl)-1-imino-2,4-bis(2-pyridylmethylimine)(L(2)s) from that with 2,4-bis(2-pyridylmethylimono)pentane (L1), trans-[FeL(1)(MeCN)(2)][ClO(4)](2).MeCN (1), and various nitriles has been determined based on the following order: C(6)F(5)CN > 3,4-difluorobenzonitrile > 4-fluorobenzonitrile > C(6)H(5)CN > C(6)H(5)CH(2)CN > C(2)H(5)CN > MeCN > Me(2)CHCN >Me(3)CN. An iron(II) complex with L1 in a cis-configuration was prepared as the ternary complex [FeL(1)(bpy)][ClO(4)](2).1.5MeNO(2).0.5H(2)O, 3a (bpy = bipyridine). Compounds 2s and 3a undergo enantiomeric interconversion with an activation energy of ca. 60 kJ mol(-1).     

Ground state of the Si(0 0 1) surface revisited—is seeing believing?

The stable structure of clean Si(0 0 1) surface around 100 K is the c(4 × 2) arrangement constructed by buckled dimers. This structure was widely accepted as the ground state in 1990’s. The view was challenged at the beginning of 2000’s by the observations of a p(2 × 1) structure below 20 K with scanning tunneling microscopy (STM). Recent experimental studies confirm that the dimer is buckled below 30 K. Large tip–surface interaction, and/or tunneling current induced dynamical effect are now experimentally evident in the STM images at low temperatures. Moreover, a current induced structure transformation is discovered below 40 K even in the study by low energy electron diffraction. Dynamical electronic and vibrational effects are theoretically studied for accounting the observation of a p(2 × 1) structure below 20 K.     

A convenient preparation of 4,8-dimethoxy-3-substituted-2(1H)-quinolones by an electrophilic reaction through base-induced deprotonation and its synthetic application for the synthesis of new alkaloids, 3,4,8-trimethoxy-2(1H)-quinolone and 3-formyl-4,7,8-trimethoxy-2(1H)-quinolone(glycocitridine)

Some 4,8-dimethoxy-3-substituted-2(1H)-quinolones were prepared by electrophilic reaction of 4,8-dimethoxy-2(1H)-quinolone with electrophiles in the presence of n-butyllithium-N,N,N',N'-tetramethylethyl-enediamine in fairly good yields. This present method was successfully applied for the synthesis of two new alkaloids bearing the 4,8-dimethoxy-2(1H)-quinolone skeleton.     

Interfacial properties of branch-tailed fluorinated surfactants yielding a water/supercritical CO2 microemulsion

We have examined the interfacial properties of several fluorinated surfactants in a water/CO2 mixture with a pendant drop tensiometer and revealed the relationships between the interfacial properties, the surfactant structure, and the microemulsifying power. We employed the following Aerosol-OT analogue surfactants that have two fluorinated tails: bis(1H,1H,5H-octafluoropentyl)-2-sulfosuccinate (di-HCF4), sodium bis(1H,1H,9H-hexadecafluorononyl)-2-sulfosuccinate (di-HCF8), sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2), and sodium bis((1H,1H,2H,2H-heptadecafluorodecyl)-oxyethylene)-2-sulfosuccinate (8FS(EO)4). To discuss the effect of the fluorocarbon/hydrocarbon ratio in single surfactant molecules, water/CO2 interfacial tension (IFT) of a hybrid surfactant with one fluorocarbon and one hydrocarbon tail, that of a surfactant with a single fluorinated tail, and that of a hydrocarbon surfactant, Aerosol-OT (AOT), were examined. The hybrid surfactant employed was sodium 1-oxo-1-[4-(tridecafluorohexyl)phenyl]-2-hexanesulfonate (FC6-HC4), and the single-tailed surfactant was perfluoropolyether ammonium carboxylate (PFPECOONH4, CF3CF2(CF2OCF(CF3))4COONH4). All of the fluorinated AOT analogue surfactants exhibited an excellent level of activity at the water/CO2 interface compared with other fluorinated surfactants and AOT. With a larger hydrocarbon chain number in the CO2-philic tails (i.e., from 0 to 2), the IFT of the AOT analogue surfactants was increased. The area occupied by one surfactant molecule at the water/CO2 interface, A, and the critical microemulsion concentration, cmicroc, were determined and used to examine the water-to-surfactant molar ratio within a reversed micelle, W0c, of the surfactants. The surfactants that form W/scCO2 microemulsions with a large W0c were found to lower the interfacial tension efficiently irrespective of increases in temperature. To achieve the most desirable W0C, the surfactant needs not only a high CO2-philicity of the tails but also a high Krafft point, properties which induce a low hydrophilic/CO2-philic balance.