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Reactions of morpholine with 4-halocoumarins 1 , 3-halocoumarins 3 , and 2-halo-l,4-naphthoquinones 8 yield two different products, one where halogen is replaced by a nucleophile at the same carbon and the other where the nucleophile is attached to the vicinal carbon away from that bearing the halogen. It is considered that reactions proceeds through nucleophilic vinylic substitution by comparision of the reaction products and deuterium exchange experiments. Plausible mechanisms for these routes are suggested. 相似文献
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Jie Eun Lee Joo Hwan Cha Ae Nim Pae Kyung II Choi Hun Yeong Koh Youseung Kim 《合成通讯》2013,43(23):4299-4308
Allylation of the C-3 position of the cephem nucleus was accomplished by either indium mediated or indium trichloride promoted tin mediated allylation reactions in aqueous media. Both methods gave 3-allyl-3-hydroxycephams 2a - 2d, in moderate to excellent yields. 相似文献
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Sang Hee Kim Hyung Gyu Kim Hyunah Choo Ae Nim Pae Bong Young Chung 《Tetrahedron letters》2006,47(36):6353-6356
N-Acyliminium ion cyclizations were studied with allenylmethylsilanes to synthesize nitrogen heterocycles. N-Acyliminium ion cyclizations were carried out by exposure of precursors 6 and 7 to Lewis acid. The precursors 6 were converted to pyrrolizidinone derivatives 9 with an exo-allene moiety, while the precursors 7 to indolizidinone derivatives 10 with an exo-1,3-diene moiety. 相似文献
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Younshil Kim Junghyun Choi Youlee Lee Taehong Kim Daejin Kim Wooyoung Jang Ki-Soo Lim Ik-Bu Sohn Jongmin Lee 《Applied Physics A: Materials Science & Processing》2010,101(1):147-152
We report femtosecond laser bonding with strengths of a few MPa and the material mixing during the laser bonding process by
using Sm3+- and Cr3+-doped glasses and 180 fs pulses at a repetition rate of 1 kHz from an amplified Ti:sapphire laser at a wavelength of 785 nm.
By analyzing fluorescence spectra taken around the interface using a confocal scanning microscope we observed the migration
of Sm ions from the upper Sm-doped glass to the lower Cr-doped glass and the reduction from Sm3+ to Sm2+ ions just above the interface for the borate-borate material system. However, in Sm-doped borate-borosilicate, the laser
bonding did not produce any reduction and migration of Sm3+ ions. 相似文献
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A concise synthesis of tetrabenazine and dihydrotetrabenazine is described. The key feature of this synthesis is the intramolecular aza-Prins-type cyclization of an amino allylsilane via oxidative C-H activation. 相似文献
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Dielectric methods have been employed to study the high-pressure behavior of a polyurethane elastomer (Solithane 113) in the vicinity of its α transition. The α-loss peak is shifted to higher temperatures and broadened somewhat with the application of hydrostatic pressure up to 6.4 kbars. The slope of Tα vs. P, or dTα/dP, obtained at low frequencies was found to be equal to dTg/dP obtained by a volumetric method. Moreover, it attained a nonzero limiting value at high pressures for each frequency tested (3—30,000 Hz) and the limiting value itself increased with increasing frequency from 10.5°C/kbar at 3 Hz to 18°C/kbar at 30,000 Hz. The activation enthalpy ΔH* was found to be nearly constant over the pressure range tested, but the activation volume ΔV* decreased with increasing pressure. The relation dTα/dP = T (ΔV*/ΔH*) was shown to hold for the elastomer. 相似文献
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Jeong GS Oh GS Pae HO Jeong SO Kim YC Shin MK Seo BY Han SY Lee HS Jeong JG Koh JS Chung HT 《Experimental & molecular medicine》2006,38(4):393-400
Recently, it has been reported that curcumin, which is known as a potent antioxidant, acts as a non- stressful and non-cytotoxic inducer of the cytoprotective heme oxygenase (HO)-1. In this study, naturally occurring curcuminoids, such as pure curcumin, demethoxycurcumin (DMC) and bis-demethoxycurcumin (BDMC), were compared for their potential ability to modulate HO-1 expression and cytoprotective activity in human endothelial cells. All three curcuminoids could induce HO-1 expression and HO activity with differential levels. The rank order of HO activity was curcumin, DMC and BDMC. In comparison with endothelial protection against H2O2-induced cellular injury, cytoprotective capacity was found to be highest with curcumin, followed by DMC and BDMC. Interestingly, cytoprotective effects afforded by curcuminoids were considerably associated with their abilities to enhance HO activity. Considering that the main difference among the three curcuminoids is the number of methoxy groups (none for BDMC, one for DMC, and two for curcumin), the presence of methoxy groups in the ortho position on the aromatic ring was suggested to be essential to enhance HO-1 expression and cytoprotection in human endothelial cells. Our results may be useful in designing more efficacious HO-1 inducers which could be considered as promising pharmacological agents in the development of therapeutic approaches for the prevention or treatment of endothelial diseases caused by oxidative damages. 相似文献
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The procedure of synthesizing the ZnS-AgAlS2 phosphor are described. It is shown that this phosphor has three emission bands and three excitation band groups for these emission bands. The temperature- and concentration-dependent shifts of the emission and excitation bands are noted along with the changes which occur in the emission band intensities with changes in temperature and concentration. An explanation of the observed effects is offered. 相似文献