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341.
An N-substituted maleimide has been used in conjunction with ketocoumarins and a tertiary amine to initiate the polymerization of 1,6-hexanedioldiacrylate in both the UV (365/366 nm) and visible region (436 nm) of the electromagnetic spectrum. The rate of polymerization of three ketocoumarin/tertiary amine combinations are significantly increased by the addition of a N-substituted maleimide, presumably due to oxidation of the coumarin ketyl radical formed by interaction between the triplet state of the ketocoumarin and the tertiary amine. 相似文献
342.
The synthesis of cyclopentanoid natural products, iridoid monoterpenes and prostaglandins, was achieved from a common intermediate 2 , which was obtained from 1 via photochemical rearrangement. 相似文献
343.
Hong Chao GUO Shang Zhong LIU Xue Tai HOU Min WANG* Department of Applied Chemistry China Agricultural University Beijing 《中国化学快报》2001,(9)
4-Amino-6-tert-butyl-3-methylthio-1, 2, 4-triazin-5 (4H)-one I, named as Metribuzin1, is an excellent selective herbicide. In the course of studying the reaction of I, we have found an unexpected reaction. We have attempted to prepare 6-tert-butyl- 4-methylamino-3-methylthio-1, 2, 4-triazin-5 (4H)-one II from I with methyl iodide in the presence of sodium hydroxide in aqueous methanol, surprisingly, instead of II the product III 4-amino-6-tert-butyl-3, 4-dihydro-2-methyl-3-thioxo-1, 2, 4-… 相似文献
344.
Summary: Carbon molecular‐sieve membranes (CMSMs) have shown great potential for gas separation. They exhibit high selectivity by permitting effective size‐ and shape‐separation between gas molecules of similar molecular dimensions. Hence, the control of their pore size is very important. While previous studies have focused on the conditions of pyrolysis and its effect on CMSM properties, a novel approach is reported here whereby the precursor polymer is chemically modified prior to pyrolysis and the resultant CMSM was investigated for its gas separation properties. Pyrolysis of chemically crosslinked and uncrosslinked Matrimid® resulted in a change in d‐spacing from 5.6 to 3.6 and 3.7 Å, respectively. The crosslinked CMSM also exhibited greater ordering in its packing. The Matrimid‐derived CMSMs exhibited excellent separation properties for CO2/CH4.
345.
Tai Kyoung Kim Ju-Mi Hong Kyung Hee Kim Se Jong Han Il-Chan Kim Hyuncheol Oh Joung Han Yim 《Molecules (Basel, Switzerland)》2021,26(21)
The pathogenesis of Alzheimer’s disease (AD) is still unclear, and presently there is no cure for the disease that can be used for its treatment or to stop its progression. Here, we investigated the therapeutic potential of ramalin (isolated from the Antarctic lichen, Ramalina terebrata), which exhibits various physiological activities, in AD. Specifically, derivatives were synthesized based on the structure of ramalin, which has a strong antioxidant effect, BACE-1 inhibition activity, and anti-inflammatory effects. Therefore, ramalin and its derivatives exhibit activity against multiple targets associated with AD and can serve as potential therapeutic agents for the disease. 相似文献
346.
Yong‐Xian Cheng Jun Zhou Ning‐Hua Tan Qi‐Tai Zheng Ning‐Bo Gong Yang Lu 《Helvetica chimica acta》2001,84(8):2343-2346
Cucubaldiol ( 1 ), a novel norsesquiterpenoid incorporating a bicyclo[2.2.2]octene ring system, was isolated from the whole plants of Cucubalus baccifer L. Its structure was determined on the basis of spectroscopic data especially by 2D‐NMR and X‐ray diffraction analyses. 相似文献
347.
Investigating the surface photografting polymerization of styrene (St), it was found that in the absence of photoinitiator and at high temperatures, a remarkable amount of St‐grafted polymer is formed. The initiation performance of St was further confirmed by surface photografting polymerization of acrylic acid, where St was used as the photoinitiator. This finding is useful to investigate the reaction mechanism of aromatic compounds under UV radiation and develop photoinitiator‐free polymerization systems. 相似文献
348.
349.
The cytotoxicities of α‐methylidene‐γ‐butyrolactones, which are linked to coumarins (see 15 and 16 ) and to potential DNA‐intercalating carriers such as flavones, xanthones, carbazole, and dibenzofuran (see 9a – e , 10a – e , 11 , and 12 ), were studied. These compounds were synthesized via alkylation of their hydroxy precursors followed by a Reformatsky‐type condensation (Scheme). These α‐methylidene‐γ‐butyralactones were evaluated in vitro against 60 human tumor cell lines derived from nine cancer cell types and demonstrated a strong growth‐inhibitory activity against leukemia cancer cells (Tables 1 and 2). For flavone‐ and xanthone‐containing α‐methylidene‐γ‐butyrolactones 9a – e and 10a – e , respectively, the overall potency (mean value) decreased on introduction of an electron‐withdrawing substituent at the γ‐phenyl substituent and increased with an electron‐donating substituent. Comparing the different chromophores established the following order of decreasing potency (log GI50): dibenzofuran ( 12 , −6.17) > flavone ( 9a , −5.96) > carbazole ( 11 , −5.80) and xanthone ( 10a , −5.77) > coumarin ( 15 , −5.60; 16 , −5.65). Among them, the dibenzofuran derivative 12 showed not only strong inhibitory activities against leukemia cancer cell lines with an average log GI50 value of −7.22, but also good inhibitory activities against colon, melanoma, and breast cancer cells with average log GI50 values of −6.23, −6.31, and −6.39, respectively. 相似文献
350.
Structural Effect on Electron Impact Decomposition of 1, 3- and 1, 4-Cyclohexane Dinitrites 下载免费PDF全文
Alkyl dinitrites have attracted attention as an important type of nitrosating agent and a pollution source in atmosphere. The reactivity and chemistry of alkyl dinitrites induced by the two ONO functional groups are relatively unknown. In this work, decompositions of 1, 3-cyclohexane dinitrite and 1, 4-cyclohexane dinitrite are studied by electron impact ionization mass spectroscopy (EI-MS). Apart from NO+ ($m/z$=30), fragment ions $m/z$=43 and 71 are the most abundant for the 1, 3-isomer. On the other hand, fragments $m/z$=29, 57, 85, and 97 stand out in the EI-MS spectrum of 1, 4-isomer. Possible dissociation mechanisms of the two dinitrites are proposed by theoretical calculations. The results reveal that the ring-opening of 1, 3-cyclohexane dinitrite mainly starts from the intermediate ion (M-NO)+ by cleavage of two $\alpha$C-$\beta$C bonds. For 1, 4-cyclohexane dinitrite, in addition to the decomposition via intermediate (M-NO)+, cleavage of $\beta$C-$\beta$C bonds can occur directly from the parent cation M+. The results will help to understand the structural related chemistry of alkyl dinitrites in atmosphere and in NO transfer process. 相似文献