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991.
3-[1′(1′H)-Substituent-pyrazol-5′-yl]benzo[5,6]coumarins and 3-(1′,2′-oxazol-5′-yl)benzo[5,6]coumarin were prepared via condensation of 3-(2′-formyl-1′-chlorovinyl)benzo[5,6] coumarin with hydrazine derivatives or hydroxylamine.Reaction of 3-[1′(1′H)-pyrazol-5′-yl]benzo[5,6]coumarin with alkyl halides,olefinic compunds or acid chlorides are described. 相似文献
992.
Yael Diskin‐Posner Goutam Kumar Patra Israel Goldberg 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(6):m344-m346
The title compound, [5,10,15,20‐meso‐tetrakis(4‐hydroxyphenyl)porphyrinato‐κ4N]zinc(II) tris(dibenzo‐24‐crown‐8) methanol tetrasolvate, [Zn(C44H28N4O4)]·3C24H32O8·4CH4O, was synthesized and its molecular structure precisely characterized by low‐temperature single‐crystal analysis. All the components are involved in hydrogen bonding with each other, thus forming an extensively hydrogen‐bonded supramolecular lattice. The functionalized porphyrin moiety coordinates both equatorially and axially to the neighboring species. 相似文献
993.
994.
Synthesis of poly(thiocarbonate)s from the copolymerization of epoxides and carbon disulfide (CS2) remains a tough challenge, due to inevitable oxygen‐sulfur atom scrambling process. In this work, we utilized the oxygen‐sulfur exchange reaction (O‐S ER) to synthesize a random copolymer with monothiocarbonate and trithiocarbonate units from CS2 and phenyl glycidyl ether (PGE) via metal‐free Lewis pairs. The copolymers contained monothiocarbonate and trithiocarbonate units of which the molar fraction could be tuned by varying either the types of Lewis pairs or the reaction temperature. Keeping track on the intermediate provided an insight in the process of O‐S ER and thus gave a hint to control the product structure. Production and consumption of phenyl thioglycidyl ether was the key process to regulate the chain structure. Remarkably, the oxygen atoms of PGE could be excluded out of the chain, resulting in the nearly complete production of poly(trithiocarbonate)s. Correspondingly, the refractive index of this kind of copolymer could be regulated in a wide range of 1.73—1.79 (at 590 nm). 相似文献
995.
Sayaka Taji Takeshi Yamada Yasuko In Shun‐ichi Wada Yoshihide Usami Kazuo Sakuma Reiko Tanaka 《Helvetica chimica acta》2007,90(11):2047-2057
Three new lanostane‐type triterpenoids, inonotsulides A, B, and C ( 1 – 3 , resp.) were isolated from the sclerotia of Inonotus obliquus (Pers .: Fr.) (Japanese name: Kabanoanatake; Russian name: Chaga). Their structures were determined to be (20R,24S)‐3β,25‐dihydroxylanost‐8‐en‐20,24‐olide ( 1 ), (20R,24R)‐3β,25‐dihydroxylanost‐8‐en‐20,24‐olide ( 2 ), and (20R,24S)‐3β,25‐dihydroxylanosta‐7,9(11)‐dien‐20,24‐olide ( 3 ) on the basis of chemical transformation, NMR spectroscopy including 1D and 2D (1H,1H‐COSY, NOESY, HMQC, HMBC), EI‐MS, and single‐crystal X‐ray analysis. 相似文献
996.
A novel type of phosphated puerarin derivatives were synthesized through a simplified Atheron‐Todd reaction for the first time. The structure of these compounds were elucidated by IR, ESI‐MS and NMR. Moreover, the reason the dialkylphophite reagent had different chemselectivities toward different hydroxys on the puerarin was discussed. 相似文献
997.
Mohammed A. Suliman Mohammed A. Gondal Mohamed A. Dastageer Gaik‐Khuan Chuah Chanbasha Basheer 《Photochemistry and photobiology》2019,95(6):1485-1494
An efficient method of photocatalytic degradation of methylparaben in water using Ag nanoparticles (NPs) loaded AgBr‐mesoporous‐WO3 composite photocatalyst (Ag/AgBr@m‐WO3), under visible light is presented. In this process, quantification of methylparaben in water was carried out by high‐performance liquid chromatography (HPLC) and the HPLC results showed a significant reduction of methylparaben in water due to the enhanced of photocatalytic degradation efficiency of Ag/AgBr@m‐WO3. For the material synthesis, highly ordered mesoporous‐WO3 (m‐WO3) was initially synthesized by sol–gel method and AgBr nanoparticles (NPs) were subsequently introduced in the pores of m‐WO3, and finally, the Ag nanoparticles were introduced by light irradiation. The enhanced photocatalytic degradation of methylparaben in water is attributed to the formation of surface plasmonic resonance (SPR) due to the introduction of Ag NPs on the surface of the catalyst. Also, the formation of heterojunction between AgBr and mesoporous‐WO3 in Ag/AgBr@m‐WO3 significantly inhibited the recombination of light‐induced electron‐hole pairs in the semiconductor composite. The morphological and optical characterizations of the synthesized photocatalysts (Ag/AgBr@m‐WO3) were carried out using SEM, TEM, XDR, N2 adsorption–desorption, UV‐VIS diffuse reflectance spectroscopy (DRS). Also, the photocatalytic studies using radical scavengers were carried out and the results indicated that is the main reactive species. 相似文献
998.
New Entrance Optics for Solar Spectral UV Measurements 总被引:2,自引:0,他引:2
The investigation of the impact of solar UV radiation on the biosphere requires spectral measurements of solar UV radiation of high accuracy. However, the accuracy of current measurements is limited, and this can partly be attributed to the entrance optics of the instruments used for these examinations. The angular response of spectro-radiometers measuring spectral global UV irradiance should be given by the cosine of the incidence angle. In-tercomparison campaigns have shown that deviations from this ideal cosine response lead to uncertainties in solar measurements of more than 10%. Here we present recently developed entrance optics that reduce these uncertainties to ±4% in the UV. The new entrance optics have been characterized with respect to their angular response, transmission, weather durability, fluorescence and dependence of the angular response on wavelength and polarization. Solar spectroradiometric measurements carried out with the new optics were compared with simultaneously performed measurements of a second spectroradiometer that was equipped with a conventional diffuser. The deviations of up to 12% between both systems are quantitatively explained to within 3%. 相似文献
999.
A series of β,γ‐unsaturated ketones were isomerized to their corresponding α,β‐unsaturated ketones by the introduction of DABCO in iPrOH at room temperature. The endo‐cyclic double bond (β,γ‐position) on ketone was rearranged to exo‐cyclic double bond (α,β‐position) under the reaction conditions. 相似文献
1000.
A general and practical procedure for the syntheses of 3,4-di-hydropyrimidine-2(1H)-thiones by a one-pot condensation of aldehyde,β-ketoester or β-diketone and thiourea using La(OTf)3 as the catalyst is described.Mild reaction conditions,excellent yields as well as the environmentally friendly character of La(OTf)3 make it an important alternative to the classic acid-catalyzed Biginelli‘s reaction. 相似文献