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31.
Kiyoshi Koyama Masato Nishimura 《Journal of polymer science. Part A, Polymer chemistry》1972,10(9):2601-2608
The polymerization of vinyl monomers initiated by binary initiator systems composed of a copper–amine complex type resin and organic halides has been studied. These binary systems initiated the polymerization of various vinyl monomers. A kinetic study of the polymerization of methyl methacrylate initiated by the copper–amine complex resin–CCl4 system was carried out, and it was found that the polymerization proceeds by way of a radical mechanism. This fact was also supported by the copolymerization of methyl methacrylate with styrene. The overall activation energy of the polymerization of methyl methacrylate was estimated as 8.4 kcal/mole. The activity of the initiator systems was greatly dependent upon the dissociation energy of carbon–halogen bonds in the organic halides. A possible initiation mechanism with the binary systems is proposed and discussed. 相似文献
32.
Diversity-oriented organic synthesis (DOS) is a key concept for construction of skeletally diverse small molecule libraries to discover drug-like small molecules. Here, we describe a DOS class to transform a complex 7-oxanorbornene skeleton, which is readily accessible by a tandem Ugi/Diels-Alder reaction, into two heterotricycle skeletons selectively by using tandem ROM/CM/RCM reaction. In the present study, the mode of cyclization is pre-encoded by building blocks used in the complexity-generating tandem Ugi/Diels-Alder reaction. Since variable alkenes can be used in the CM reaction, our approach can be extended to construct both skeleton- and appendage-diverse small molecule libraries. 相似文献
33.
Poon TS Kuchel JM Badruddin A Halliday GM Barnetson RS Iwaki H Hatao M 《Photochemistry and photobiology》2003,78(4):331-336
Very little information exists on the amount of natural and artificial UV light required to cause sunburn and tanning in individuals with very pale skin who are at the greatest risk of developing skin cancer. We have investigated minimal erythema dose (MED) and minimal melanogenic dose (MMD) in a group of 31 volunteers with Fitzpatrick skin types I and II using an Oriel 1000 W xenon arc solar simulator and natural sunlight in Sydney, Australia. We measured the erythemal and melanogenic responses using conventional visual scoring, a chromameter and an erythema meter. We found that the average MED measured visually using the artificial UV source was 68.7 +/- 3.3 mJ/cm2 (3.4 +/- 0.2 standard erythema doses [SED]), which was significantly different from the MED of sunlight, which was 93.6 +/- 5.6 mJ/cm2 (P < 0.001) (11.7 +/- 0.7 SED). We also found significant correlations between the solar-simulated MED values, the melanin index (erythema meter) and the L* function (chromameter). The average MMD (obtained in 16 volunteers only) using solar-simulated light was 85.6 +/- 4.9 mJ/cm2, which was significantly less than that measured with natural sunlight (118.3 +/- 8.6 mJ/cm2; P < 0.05). We mathematically modeled the data for both the chromameter and the erythema meter to see if we were able to obtain a more objective measure of MED and differentiation between skin types. Using this model, we were able to detect erythemal responses using the erythema index function of the erythema meter and the a* function of the chromameter at lower UV doses than either the standard visual or COLIPA methods. 相似文献
34.
Nambu H Hata K Matsugi M Kita Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(2):719-727
The combination of the water-soluble radical initiator, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044) and the surfactant, cetyltrimethyl-ammonium bromide (CTAB), was found to be the most suitable condition for the effective and direct synthesis of useful active thioesters (pentafluorophenyl thioesters) in water. In addition, the direct amidation of aldehydes was achieved by the addition of the amines to the thioesterification reaction mixture in water. 相似文献
35.
Here, we report a diversity-oriented synthetic approach toward skeletally diverse, cyclized peptidomimetics with diverse appendages. Starting from α-(N-acylamino)amides with various appendages, 12 to 16-membered lactams with defined olefin geometry were synthesized by a common synthetic sequence. We also synthesized the macrocycle in a liquid phase directed toward a construction of the peptidomimetics library. 相似文献
36.
Imai M Tanaka M Tanaka K Yamamoto Y Imai-Ogata N Shimowatari M Nagumo S Kawahara N Suemune H 《The Journal of organic chemistry》2004,69(4):1144-1150
Intermolecular hydroacylation between salicylaldehydes 1, 26-40 and 1,4-penta- or 1,5-hexadienes 4-13 by Rh-catalyst proceeded under mild reaction conditions to give a mixture of iso- and normal-hydroacylated products 14-25, 41-55, and 57-60. In the hydroacylation reaction, chelation of both salicylaldehyde and diene to the Rh-complex plays a crucial role. The ratio of iso- and normal-hydroacylated products could be regulated by the addition of salicylic acid or amines. The effects of various Rh-complexes, solvents, and additives were examined, and the plausible mechanisms of the catalytic cycle were proposed on the basis of the deuterium-labeling salicylaldehyde experiments. 相似文献
37.
Du YZ Hiratsuka Y Taira S Eguchi M Uyeda TQ Yumoto N Kodaka M 《Chemical communications (Cambridge, England)》2005,(16):2080-2082
A new nano-biomachine has been created from microtubules (MTs) and hetero-bifunctional polymer particles bearing pyruvate kinase, which is propelled on glass surfaces coated with kinesin by use of self-supplying ATP. 相似文献
38.
Masato Machida 《Catalysis Surveys from Asia》2002,5(2):91-102
(n)MnOx–(1?n)CeO2 binary oxides have been studied for the sorptive NO removal and subsequent reduction of NOx sorbed to N2 at low temperatures (≤150 °C). The solid solution with a fluorite-type structure was found to be effective for oxidative NO adsorption, which yielded nitrate (NO? 3) and/or nitrite (NO? 2) species on the surface depending on temperature, O2 concentration in the gas feed, and composition of the binary oxide (n). A surface reaction model was derived on the basis of XPS, TPD, and DRIFTS analyses. Redox of Mn accompanied by simultaneous oxygen equilibration between the surface and the gas phase promoted the oxidative NO adsorption. The reactivity of the adsorbed NOx toward H2 was examined for MnOx–CeO2 impregnated with Pd, which is known as a nonselective catalyst toward NO–H2 reaction in the presence of excess oxygen. The Pd/MnOx–CeO2 catalyst after saturated by the NO uptake could be regenerated by micropulse injections of H2 at 150 °C. Evidence was presented to show that the role of Pd is to generate reactive hydrogen atoms, which spillover onto the MnOx–CeO2 surface and reduce nitrite/nitrate adsorbing thereon. Because of the lower reducibility of nitrate and the competitive H2–O2 combustion, H2–NO reaction was suppressed to a certain extent in the presence of O2. Nevertheless, Pd/MnOx–CeO2 attained 65% NO-conversion in a steady stream of 0.08% NO, 2% H2, and 6% O2 in He at as low as 150 °C, compared to ca. 30% conversion for Pd/γ–Al2O3 at the same temperature. The combination of NOx-sorbing materials and H2-activation catalysts is expected to pave the way to development of novel NOx-sorbing catalysts for selective deNOx at very low temperatures. 相似文献
39.
Yamanaka N Kawano R Kubo W Kitamura T Wada Y Watanabe M Yanagida S 《Chemical communications (Cambridge, England)》2005,(6):740-742
Use of a new ionic liquid crystal, 1-dodecyl-3-methylimidazolium iodide, and iodine as an electrolyte of dye-sensitized solar cells leads to a high short circuit photocurrent density and a high light-to-electricity conversion efficiency, due to a self-assembled structure of the imidazolium cations, resulting in high conductivity of the electrolyte. 相似文献
40.
3-Alkylthio-4-amino-1,6-dihydro-1,2,4-triazin-5(4H)-ones were synthesized by the reduction of 3-thio-4-amino-1,2,4-triazine-3,5(2.H,4H)-diones and successive S-alkylation. The regiospecific alkylation on the N-1 position or the exo amino group leads to a variety of 1,6-dihydro-1,2,4-triazin-5(4H)-one derivatives. An alternative synthesis of 3-thio-4-amino-1,6-dihydro-1,2,4-triazine-3,5(2H,4H)-diones was accomplished through the cyclization of 1-thiocarbohydrazidoacetamide derivatives. 相似文献