Vinyl polymerization. 413. Polymerization of vinyl monomer initiated by poly(vinylbenzyltrimethyl)-ammonium chloride

The polymerization of vinyl monomer initiated by an aqueous solution of poly(vinylbenzyltrimethyl)ammonium chloride (Q-PVBACI) was carried out at 85°C. Styrene, p-chlorostyrene, methyl methacrylate, and i-butyl methacrylate were polymerized, whereas acrylonitrile and vinyl acetate were not. The effects of the amounts of vinyl monomer, Q-PVBACI, and water on the conversion of vinyl monomer were studied. The overall activation energy in the polymerization of styrene was estimated as 79.1 kJ mol^?1. The polymerization proceeded through a radical mechanism. The selectivity of vinyl monomer was discussed by “a concept of hard and soft hydrophobic areas and monomers.”     

Two New Spermidine Alkaloids from Chisocheton weinlandii

The investigation of the MeOH extract of the leaves of Chisocheton weinlandii Harms (Meliaceae) revealed two new open‐chain spermidine alkaloids, chisitine 1 ( 1 ) and chisitine 2 ( 2 ). Their structures were elucidated by NMR spectroscopy, tandem‐mass spectrometry, and independant syntheses (Scheme 3). Detailed MS/MS fragmentation pathways are discussed for both compounds based on H/D exchange and ¹⁸O‐labeling experiments (Schemes 1 and 2).     

Cationic polymerization of γ-methyl- and α-methylphenylallene

The cationic polymerizations of γ-methylphenylallene ( 1 ) and α-methylphenylallene ( 2 ) were carried out with some Lewis acids at 25 and 0°C in dichloromethane to obtain the corresponding polymers through allyl cations, respectively. Tin (IV) chloride was found to be an effective catalyst for the cationic polymerization of both allenes 1 and 2 compared with other Lewis acids. Thus, in the polymerization of 1 , methanol-insoluble polymer was only obtained using Tin (IV) chloride, and M?_n of methanol-insoluble polymer obtained by Tin (IV) chloride was the highest in the polymerization of 2 . From the analysis of ¹H- and ¹³C-NMR spectra of the obtained polymers, the polymer from 1 consisted of two kinds of units polymerized by each double bonds of allene 1 , whereas the polymer from 2 consisted of only one unit polymerized by terminal double bond of allene 2 . Moreover, effect of solvent on the cationic polymerizations of 1 and 2 were discussed.     

Complex formation of poly(4-vinyl-N-alkylpyridinium) salts or polymer containing flavin mononucleotide with indole derivatives

A charge-transfer-type complex formation between poly(4-vinyl-N-propylpyridinium bromide) (C3PVP), poly(4-vinyl-N-butylpyridinium bromide) (C4PVP) or poly(4-vinyl-N-benzylpyridinium chloride) (BzPVP), and indole derivatives or between polymer containing flavin mononucleotide residues and indole derivatives was studied in the presence of simple and polyelectrolytes. The association constant (K) of the complex formation with indole acetate increased in the order BzPVP > C4PVP > C3PVP, which indicated an important contribution by hydrophobic interaction. The addition of simple and polyelectrolytes decreased the association constants. This was explained by the “secondary salt effect” of the salts. The importance of the electrostatic interactions in the complexation systems was obvious. The influence of simple electrolytes on the K values was discussed theoretically according to Manning's theory.     

Photochemical study of [3(3)](1,3,5)cyclophane and emission spectral properties of [3n]cyclophanes (n = 2-6)

Thephotochemical reaction of [3(3)](1,3,5)cyclophane 2, which is a photoprecursor for the formation of propella[3(3)]prismane 18, was studied using a sterilizing lamp (254 nm). Upon photolysis in dry and wet CH2Cl2 or MeOH in the presence of 2 mol/L aqueous HCl solution, the cyclophane 2 afforded novel cage compounds comprised of new skeletons, tetracyclo[6.3.1.0.(2,7)0(4,11)]dodeca-5,9-diene 43, hexacyclo[6.4.0.0.(2,6)0.(4,11)0.(5,10)0(9,12)]dodecane 44, and pentacyclo[6.4.0.0.(2,6)0.(4,11)0(5,10)]dodecane 45. All of these products were confirmed by the X-ray structural analyses. A possible mechanism for the formation of these photoproducts via the hexaprismane derivative 18 is proposed. The photophysical properties in the excited state of the [3n]cyclophanes ([3n]CP, n = 2-6) were investigated by measuring the emission spectra and determining the quantum yields and lifetimes of the fluorescence. All [3n]CPs show excimeric fluorescence without a monomeric one. The lifetime of the excimer fluorescence becomes gradually longer with the increasing number of the trimethylene bridges. The [3n]CPs also shows excimeric phosphorescence spectra without vibrational structures for n = 2, 4, and 5, while phosphorescence is absent for n = 3 and 6. With an increase in symmetry of the benzene skeleton in the [3(3)]- and [3(6)]CPs, the probability of the radiation (phosphorescence) process from the lowest triplet state may drastically decrease.     

Selective hydrogenation of benzophenones to benzhydrols. Asymmetric synthesis of unsymmetrical diarylmethanols

[reaction: see text] trans-RuCl2[P(C6H4-4-CH3)3]2(NH2CH2CH2NH2) acts as a highly effective precatalyst for the hydrogenation of a variety of benzophenone derivatives to benzhydrols that proceeds smoothly at 8 atm and 23-35 degrees C in 2-propanol containing t-C4H9OK with a substrate/catalyst ratio of 2000-20000. Use of a BINAP/chiral diamine Ru complex effects asymmetric hydrogenation of various ortho-substituted benzophenones and benzoylferrocene to chiral diarylmethanols with consistently high ee.     

Ring‐Opening Reactions of 3‐Aryl‐1‐benzylaziridine‐2‐carboxylates and Application to the Asymmetric Synthesis of an Amphetamine‐Type Compound

Nucleophilic ring‐opening reactions of 3‐aryl‐1‐benzylaziridine‐2‐carboxylates were examined by using O‐nucleophiles and aromatic C‐nucleophiles. The stereospecificity was found to depend on substrates and conditions used. Configuration inversion at C(3) was observed with O‐nucleophiles as a major reaction path in the ring‐opening reactions of aziridines carrying an electron‐poor aromatic moiety, whereas mixtures containing preferentially the syn‐diastereoisomer were generally obtained when electron‐rich aziridines were used (Tables 1–3). In the reactions of electron‐rich aziridines with C‐nucleophiles, S_N2 reactions yielding anti‐type products were observed (Table 4). Reductive ring‐opening reaction by catalytic hydrogenation of (+)‐trans‐(2S,3R)‐3‐(1,3‐benzodioxol‐5‐yl)aziridine‐2‐carboxylate (+)‐trans‐ 3c afforded the corresponding α‐amino acid derivative, which was smoothly transformed into (+)‐tert‐butyl [(1R)‐2‐(1,3‐benzodioxol‐5‐yl)‐1‐methylethyl]carbamate((+)‐ 14 ) with high retention of optical purity (Scheme 6).     

Study on the thermal stability of a chiral stationary phase coated on capillaries for GC

A chiral stationary phase prepared by bonding L -valine-t-butylamide to XE-60 has been coated on glass and metal capillaries. The performances of the chiral glass and metal columns were equivalent to those of commercial fused silica capillary columns. The thermal stability of the glass column was examined up to 280°C. It was found that no appreciable change in separation factor (α value) was observed up to 230°C. The α values gradually decreased between 240 and 260°C, and enantiomer separation was no longer achieved at 280°C. It was concluded that the allowable upper limit temperature of the chiral stationary phase is between 230 and 240°C in the isothermal mode, and ca 260°C in temperature-programmed mode.     

Ionic conductivity of superionic conducting glasses in the pseudobinary system AgIAg2MoO4

The ionic conductivity was measured in the temperature range 250–300 K as a function of composition of superionic conducting glasses in the pseudobinary system AgIAg₂MoO₄. The conductivity, ranging from 10^?2 to 10^?4 Ω^?1 cm^?1 at room temperature, increases linearly in logarithmic scale with increasing AgI content, while the total silver ion concentration remains nearly constant in the whole glass-forming region of the present system. Such a composition dependence of conductivity is considered to be evidence that only a fraction of the silver ions in glass contributes to the ionic conduction. The conductivity and the activation energy for conduction differ slightly between bulk glasses and pressed pellets of pulverized glasses. The close agreement in bulk glasses and pellets suggests that bulk rather than grain boundary or surface diffusion dominates the conduction process in the present glasses.     

Isolation and crystal structure of a water-soluble iridium hydride: a robust and highly active catalyst for acid-catalyzed transfer hydrogenations of carbonyl compounds in acidic media

This paper reports the isolation and structural determination of a water-soluble hydride complex [Cp*Ir(III)(bpy)H](+) (1, Cp* = eta(5)-C(5)Me(5), bpy = 2,2'-bipyridine) that serves as a robust and highly active catalyst for acid-catalyzed transfer hydrogenations of carbonyl compounds at pH 2.0-3.0 at 70 degrees C. The catalyst 1 was synthesized from the reaction of a precatalyst [Cp*Ir(III)(bpy)(OH(2))](2+) (2) with hydrogen donors HCOOX (X = H or Na) in H(2)O under controlled conditions (2.0 < pH < 6.0, 25 degrees C) which avoid protonation of the hydrido ligand of 1 below pH ca. 1.0 and deprotonation of the aqua ligand of 2 above pH ca. 6.0 (pK(a) value of 2 = 6.6). X-ray analysis shows that complex 1 adopts a distorted octahedral geometry with the Ir atom coordinated by one eta(5)-Cp*, one bidentate bpy, and one terminal hydrido ligand that occupies a bond position. The isolation of 1 allowed us to investigate the robust ability of 1 in acidic media and reducing ability of 1 in the reaction with carbonyl compounds under both stoichiometric and catalytic conditions. The rate of the acid-catalyzed transfer hydrogenation is drastically dependent on pH of the solution, reaction temperature, and concentration of HCOOH. The effect of pH on the rate of the transfer hydrogenation is rationalized by the pH-dependent formation of 1 and activation process of the carbonyl compounds by protons. High turnover frequencies of the acid-catalyzed transfer hydrogenations at pH 2.0-3.0 are ascribed not only to nucleophilicity of 1 toward the carbonyl groups activated by protons but also to a protonic character of the hydrido ligand of 1 that inhibits the protonation of the hydrido ligand.