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11.
12.
Microgel-like poly(allyl methacrylate) (PAMA nanosphere) was prepared by the emulsion polymerization of AMA as the reactive crosslinked polymer nanosphere with abundant pendant allyl groups. The terpolymerization of PAMA nanosphere with allyl benzoate (ABz) and vinyl benzoate (VBz) was conducted in bulk using benzoyl peroxide as initiator at 80 °C. The gelation depended on the feed ABz/VBz molar ratio since the molecular weights of resulting poly(ABz-co-VBz)s that act as the bridges increased with an increase in the mole fraction of VBz in the feed monomer. Beyond the gel point, the sol was rapidly incorporated into the gel and the increasing tendency of the gel fraction became steeper from 70 to 95 mol% of VBz as a reflection of increased chain length of bridge between PAMA nanospheres. Moreover, the swelling ratio became lower with increasing the mole percentage of VBz in the feed monomer. These results would support the preferential incorporation of PAMA nanosphere into the gel and the longer bridge can capture more nanospheres to give a much shrunken gel. 相似文献
13.
A cationic CpRu(II) complex in combination with quinaldic acid shows high reactivity and chemoselectivity for the catalytic deprotection of hydroxyl groups protected as allyl ethers. The catalyst operates in alcoholic solvents without the need for any additional nucleophiles, satisfying the practical requirements of operational simplicity, safety, and environmental friendliness. The wide applicability of this deprotection strategy to a variety of multifunctional molecules, including peptides and nucleosides, may provide new opportunities in protective group chemistry. [structure: see text] 相似文献
14.
The separation of diastereomeric esters derived from (±)-pyridylethanols and 3β-acetoxyetienic acid were achieved by an extraction technique using diethyl ether and aqueous hydrochloric acid. A formal total synthesis of PNU-142721 was effectively carried out to prepare the chiral, non-racemic synthon 1-furo[2,3-c]pyridin-5-yl-ethanol (1) by means of this technique. The structure optimized using MOPAC calculations on each diastereomer suggested the presence of intramolecular CH/π interaction in only the (S)-isomer of the diastereomers. 相似文献
15.
Masato ItoAkihide Osaku Sachiko KitaharaMakoto Hirakawa Takao Ikariya 《Tetrahedron letters》2003,44(40):7521-7523
A ternary catalyst system of Cp*RuCl(cod)-2-diphenylphosphinoethylamine-KOt-Bu (Cp*=η5-C5(CH3)5, cod=1,5-cyclooctadiene) causes rapid racemization of chiral non-racemic sec-alcohols, which results from the reversible hydrogen transfer between sec-alcohols and ketones. Both tertiary phosphine and primary amine functionalities in the ligand are responsible for the high rate. 相似文献
16.
Shin-ichiro Shoda Yoshinori Misawa Yousuke Nishijima Yukiko Tawata Tomohiko Kotake Masato Noguchi Atsushi Kobayashi Takeshi Watanabe 《Cellulose (London, England)》2006,13(4):477-484
Chitinase-catalyzed hydrolytic and transglycosylating behavior of 1,2-oxazoline derivative of N-acetyllactosamine (LacNAc-oxa) 1 has been investigated. An extremely rapid hydrolysis (ring-opening of the oxazoline moiety) could be observed, suggesting that 1 behaves as a transition state analogue substrate for chitinase A1 (Bacillus circulans WL-12). This disaccharide monomer 1 was found to polymerize under basic conditions, giving rise to novel oligosaccharides having a β(1-4)–β(1-6) repeating unit in the main chain. The degree of polymerization of the resulting oligosaccharides was up to 5. This is the first example of enzymatic glycosylation reaction forming a β(1-6) bond catalyzed by chitinase. 相似文献
17.
A series of parallel reactions were carried out for the tandem Ugi/Diels-Alder reaction on our MPEG-O-CH2- platform. Ninety-six out of a 100 entries were successful to give complex heterotricycles. The stereoselectivity was found not to be influenced by the building blocks used for amine and carboxylic acid components. An unexpected side pathway was found but was suppressed by employing appropriate reaction conditions. The reaction was also performed on solid phase, by which a larger library is potentially realized by employing the split-pool method. 相似文献
18.
Nagao M Asano K Umeda K Katayama H Ozawa F 《The Journal of organic chemistry》2005,70(25):10511-10514
[reaction: see text] Complex 1 bearing a diphosphinidenecyclobutene ligand (DPCB-OMe) catalyzes highly stereoselective hydrosilylation of diethynylarenes with HSiMe2Ph to afford (Z,Z)-bis(2-silylethenyl)arenes. Treatment of the hydrosilylation products with N-bromosuccinimide causes bromodesilylation in a stereospecific manner, giving (Z,Z)-bis(2-bromoethenyl)arenes in high geometrical purity (>98%). 相似文献
19.
Shizuko Hirata Yukimasa Hashimoto Masato Aihara G. Vitharana Mallika 《Fresenius' Journal of Analytical Chemistry》1996,355(5-6):676-679
A flow-injection method for the determination of dissolved cobalt(II) in sea water has been studied based on a combination of column preconcentration using 8-quinolinol immobilized on silica gel, fluoride containing metal alkoxide glass (8HQ-MAF) and chemiluminescence detection with a gallic acid-hydrogen peroxide system. Co(II) is selectively recovered from an acidified sample with 8-quinolinol immobilized on silica gel. After elution with dilute hydrochloric acid the resultant eluent is mixed with the reagent solutions, heated to 60°C and then introduced into the CL cell. The analysis time including the 2-min sample load was 8 min per sea water sample with a corresponding detection limit of 0.62 ngl-1 (3). The average standard deviation calculated for 10 replicate measurements of artificial sea water samples with a concentration of 10 ngl-1 cobalt was ±2.1%. The method has been tested with the standard reference sea waters NASS and CASS. 相似文献
20.
A home made column of commercially available iminodiacetate resin, Muromac A-1 (50–100 mesh) was used to concentrate rare earth elements (REEs) (15 elements: Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in seawater. An automated low pressure flow analysis method with on-line column preconcentration/inductively coupled plasma mass spectrometry (ICP-MS) is described for the determination of REEs in seawater. Sample solutions (adjusted to pH of 3.0) passed through the column. After washing the column with water, the adsorbed elements were subsequently eluted into the plasma with 0.7 M nitric acid. Calibration curves were accomplished by means of purified artificial seawater with a sample loading time of 120 s. Detection limits (DLs) of the on-line column preconcentration/ICP-MS by eight replicate operations were between 0.040 and 0.251 pg ml−1 for REEs in the artificial seawater. The precision was less than 8.9% for REEs and one sample can be processed in 7 min using a 7 ml of sample. The proposed method was applied to determine REEs in coastal seawater of Hiroshima Bay, Japan. 相似文献