Dechlorination of poly(vinylidene chloride) in NaOH/ethylene glycol as a function of NaOH concentration, temperature, and solvent

The wet dechlorination treatment of poly(vinylidene chloride) (PVDC) was evaluated at atmospheric pressure in a solution of NaOH in ethylene glycol (EG), as a function of NaOH concentration, temperature, and solvent. Hydroxide ion from NaOH was required for dechlorination with EG acting solely as a solvent. The wet treatment exhibited significantly enhanced dechlorination efficiency over traditional thermal techniques, with a reaction efficiency as high as 92.8% in 1.0 M NaOH at 190 °C. Dechlorination reactions of PVDC in both NaOH/EG and NaOH/H₂O were expressed by an apparent first-order reaction. At 190 °C, the apparent rate constant in 1.0 M NaOH/EG was approximately 1.4 times larger than in 1.0 M NaOH/H₂O, with an apparent activation energy of 82.8 kJ mol⁻¹, indicating that the reaction proceeded under chemical control. The degree of dechlorination increased with increasing reaction temperature, favouring the elimination of HCl over the hydroxyl substitution of chloride.     

Brønsted acid catalyzed regioselective aza-Ferrier reaction: a novel synthetic method for alpha-(N-Boc-2-pyrrolidinyl) aldehydes

The 1,4-elimination reaction of (Z)-N-Boc-2-(4-methoxy-2-alkenyloxy)pyrrolidines is shown to proceed with high (1E,3E)-stereoselectivity to afford N-Boc-2-(1,3-dienyloxy)pyrrolidines; the Br?nsted acid catalyzed aza-Ferrier reaction of the N-Boc-2-(1,3-dienyloxy)pyrrolidines (3) provides alpha-(N-Boc-2-pyrrolidinyl) aldehydes in excellent yields with high alpha-regioselectivities.     

Functionalization of silicon surfaces with catalytically active Pd complexes and application to the aerobic oxidation of benzylic alcohols

A single-crystal silicon surface was modified with a bisoxazoline-Pd molecular layer and utilized as a highly efficient (catalyst turnover number up to 780,000, 110 degrees C, 72 h) and recyclable catalyst in the aerobic oxidation of benzylic alcohols.     

Enumerating 3-manifolds with lengths up to 9 by a canonical order

On previous works, we enumerated the prime links with lengths up to 10 and the prime link exteriors with lengths up to 9. In this paper, we make an enumeration of the first 133 closed 3-manifolds which are the 3-manifolds with lengths up to 9 by using the enumeration of the prime link exteriors.     

Photosensitive polybenzoxazole based on a poly(o‐hydroxy amide), a dissolution inhibitor,and a photoacid generator

A positive‐type photosensitive polybenzoxazole (PSPBO), based on a poly(o‐hydroxy amide) (PHA), the dissolution inhibitor (DI) 9,9‐bis(4‐tert‐butoxycarbonyloxyphenyl)fluorene (t‐Boc BHF), and the photoacid generator (5‐propylsulfonyloxyimino‐5H‐thiophene‐2‐ylidene)‐(2‐methylphenyl)acetonitrile (PTMA), was developed. Several new tert‐butoxycarbonylated compounds as DIs for PSPBOs were prepared from phenolic compounds having a cardolike structure with di‐tert‐butyl dicarbonate in the presence of 4‐dimethylaminopyridine. Among them, t‐Boc BHF and 5,5′,6,6′‐tetra(tert‐butoxycarbonyl)‐3,3,3′,3′‐tetramethyl‐1,1′‐spirobiindane acted as excellent DIs, giving a large dissolution contrast between the exposed and unexposed areas in a 2.38 wt % tetramethylammonium hydroxide solution (TMAHaq)/5 wt % iso‐propanol (i‐PrOH). The dissolution behavior of this PSPBO system was studied in relation to the PTMA and t‐Boc BHF loadings and postexposure baking temperature. A PSPBO consisting of PHA (77 wt %), t‐Boc BHF (20 wt %), and PTMA (3 wt %) exhibited a sensitivity of 34 mJ/cm² and a contrast of 5.8 when exposed to 365‐nm light (i‐line) and developed with an aqueous alkaline developer, 2.38 wt % TMAHaq/5 wt % i‐PrOH. A clear, positive image with 6‐μm features and a 10‐μm‐thick pattern with high sensitivity and contrast was produced by contact printing and converted into polybenzoxazole patterns upon heating at 350 °C for 1 h. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 661–668, 2007     

Application of biphasic reaction procedure using ferric chloride dissolved in an imidazolium salt and benzotrifluoride (FeIm-BTF procedure) to aza-Prins cyclization reaction

Aza-Prins cyclization reaction of N-tosyl-3-butenylamine with aliphatic and aromatic aldehydes was performed using a combination of FeCl₃ and 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF₆) or 1-butyl-3-methylimidazolium tetrachloroferrate (BmimFeCl₄) in benzotrifluoride (BTF). The desired N-tosyl-4-chloro-2-substituted piperidines were obtained from aliphatic aldehydes in comparable yields to those for the previously reported reactions in which FeCl₃ was used in CH₂Cl₂. On the other hand, significant progress for the piperidine synthesis from aromatic aldehydes has been achieved, particularly when BmimFeCl₄ was used with FeCl₃ in BTF.     

Salt tolerance of an aqueous solution of a novel amphiphilic polysaccharide derivative

An aqueous solution of an amphiphilic polysaccharide derivative, hydrophobically (stearyl alkyl group) and hydrophilically (sulfonic-acid salt group) modified hydroxyethylcellulose (HHM-HEC), showed increased viscosity, elasticity, and thixotropic properties in response to the addition of monovalent and divalent salts. Furthermore, the HHM-HEC solution had a transparent appearance at a NaCl concentration of 7 wt %. Since it showed superior salt tolerance to HEC, we focused attention on the two substituents of HHM-HEC and prepared HEC derivatives, namely, hydrophobically modified hydroxyethylcellulose (R-HEC), hydrophilically modified hydroxyethylcellulose (S-HEC), and nonmodified hydroxyethylcellulose (HEC). In addition, we used oscillatory, thixotropic, and fluorometric methods to compare the rheological properties of HHM-HEC with those of other derivatives in the presence of NaCl and ZnCl2, and attempted to elucidate the respective roles of the two substituents of HHM-HEC solution in the salt-tolerance mechanism. As the NaCl concentration in the HHM-HEC solution increased, the values of the elastic modulus G' and the viscous modulus G' increased, and, moreover, the relative intensities of the first (I1 = 372 nm) and the third (I3 = 383 nm) vibronic bands of the pyrene monomer emission spectrum (the I1/I3 ratio) decreased. These results suggested that the added salt strengthened the three-dimensional network structure of the HHM-HEC polymer by the formation of cross-linkages through the association of hydrophobic substituents. This hydrophobic substituent was therefore essential in allowing HHM-HEC to exhibit a high viscosity in a salt solution. Although the R-HEC solution showed a higher viscosity than did the HHM-HEC solution in the absence of added salts, it became cloudy and lost its viscosity at high NaCl concentrations, apparently because of the shrinkage of its network structure. This signified that the hydrophilic substituent was essential for the sufficient solubility of HHM-HEC to show its rheological properties in a salt-rich solution. We propose to explain how the viscosity of HHM-HEC increases in the presence of salts as follows: Added salts weaken the electrostatic repulsion between the hydrophilic substituents, thereby enhancing the interactions of hydrophobic substituents and consequently increasing the rigidity of the HHM-HEC solution.     

1,2-Dimethoxy-4,5-dimethylene: a new protecting group for acyclic amino acid derivatives prepared by Stevens rearrangement

A new protecting group, 1,2-dimethoxy-4,5-dimethylene, for acyclic amino acid derivatives could be introduced by N,N-dialkylation with 1,2-bis(bromomethyl)-4,5-dimethoxybenzene (1) and removed via amine de-alkylation with acyl chlorides. The method can be used with base-induced [2,3] and [1,2] Stevens rearrangement products.     

Local Whittle likelihood estimators and tests for non-Gaussian stationary processes

In this paper, we propose a local Whittle likelihood estimator for spectral densities of non-Gaussian processes and a local Whittle likelihood ratio test statistic for the problem of testing whether the spectral density of a non-Gaussian stationary process belongs to a parametric family or not. Introducing a local Whittle likelihood of a spectral density f _θ (λ) around λ, we propose a local estimator [^(q)] = [^(q)] (l){\hat{\theta } = \hat{\theta } (\lambda ) } of θ which maximizes the local Whittle likelihood around λ, and use f_{[^(q)] (l)} (l){f_{\hat{\theta } (\lambda )} (\lambda )} as an estimator of the true spectral density. For the testing problem, we use a local Whittle likelihood ratio test statistic based on the local Whittle likelihood estimator. The asymptotics of these statistics are elucidated. It is shown that their asymptotic distributions do not depend on non-Gaussianity of the processes. Because our models include nonlinear stationary time series models, we can apply the results to stationary GARCH processes. Advantage of the proposed estimator is demonstrated by a few simulated numerical examples.