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31.
Ariel Carreño-Montero Luis A. Maldonado María Isabel Chávez Simón Hernández-Ortega Guillermo Delgado 《Tetrahedron letters》2019,60(48):151282
The synthesis of ethyl (2′-hydroxy-4′,5′-methylendioxophenyl)acetate, a fragment of the antihyperglycemic natural coumarin subcoriacin, is reported. We found an expeditious route to the title compound in five steps. Final metal catalyzed acid ethanolysis of the vinylic 1,1-methylthio methylsulfoxide derivative afforded the required aryl acetic ester, but in the absence of metal catalyst, an unexpected Pummerer rearrangement produced the 2,3-dimethylthiofuran derivative as the major product. This last result provides an alternative entry to 2,3-dimethlythiobenzofurans. 相似文献
32.
V. D. Maiorov V. V. Burdin G. I. Voloshenko N. B. Librovich 《Russian Chemical Bulletin》1996,45(7):1766-1769
The multiple attenuated total reflection IR spectra of solutions of sodium acetate in acetic acid have been recorded in the range from 9000 to 4000 cm–1. The CH3COO– anion and an acid molecule form be complex (CH3COO...H...OOCCH3) with a strong symmetric H-bond.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp, 1854–1857, July, 1996. 相似文献
33.
34.
Chemical surface modifications of microfibrillated cellulose 总被引:1,自引:0,他引:1
Per Stenstad Martin Andresen Bjørn Steinar Tanem Per Stenius 《Cellulose (London, England)》2008,15(1):35-45
Microfibrillated cellulose (MFC) was prepared by disintegration of bleached softwood sulphite pulp through mechanical homogenization.
The surface of the MFC was modified using different chemical treatments, using reactions both in aqueous- and organic solvents.
The modified MFC was characterized with fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS)
and transmission electron microscopy (TEM). Epoxy functionality was introduced onto the MFC surface by oxidation with cerium
(IV) followed by grafting of glycidyl methacrylate. The length of the polymer chains could be varied by regulating the amount
of glycidyl methacrylate added. Positive charge was introduced to the MFC surface through grafting of hexamethylene diisocyanate,
followed by reaction with the amines. Succinic and maleic acid groups could be introduced directly onto the MFC surface as
a monolayer by a reaction between the corresponding anhydrides and the surface hydroxyl groups of the MFC. 相似文献
35.
以马来酸酐和丙烯酸为单体,过硫酸钾为引发剂,合成马来酸酐丙烯酸的共聚物,然后在它们的共聚物中加入无机盐,复配制成肥料防结块剂。结果表明最佳优化工艺条件为:丙烯酸和顺酐的摩尔比为1:2;引发剂用量为4%;反应温度为80℃—85℃;反应时间为3h;固含量设计为35%左右,其防结块效果与聚丙烯酸钠的同类产品对比更佳。 相似文献
36.
Jeong Ah Chang 《Journal of solid state chemistry》2009,182(4):749-756
Nanosized anatase and rutile TiO2 having different shape, phase and size have been prepared from aqueous solutions of peroxo titanium complex starting from titanium(IV) isopropoxide (TTIP), acetic acid and hydrogen peroxide (H2O2) in water/isopropanol media by a facile sol-gel process. The TiO2 nanocrystals are characterized by powder X-ray diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, TEM, high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) techniques. The influence of pH and the sequence of addition of reaction contents on the phase and morphology of TiO2 are studied. The reasons for the observation of only anatase and/or mixture of anatase and rutile are given. 相似文献
37.
To date, the synthesis of peptides is concurrent with the production of enormous amounts of toxic waste. DMF, CH2Cl2, and NMP are three of the most toxic organic solvents used in chemical synthesis and are the most common solvents used for peptide synthesis. Additionally, concerns about the hepatotoxicity caused by exposure to DMF and from the toxic and allergenic nature of additives used in peptide synthesis necessitates the need for a green, environmentally friendly, and safer protocol for peptide synthesis. This review summarizes the current literature on green solid‐phase peptide synthesis successes and challenges encountered. The review concludes with suggestions for future research towards a simple and efficient green peptide synthesis protocol. 相似文献
38.
Anufriev V. Ph. Polonik S. G. Pokhilo N. D. Balanyova N. N. 《Russian Chemical Bulletin》2003,52(10):2247-2250
The Friedel—Crafts acylation of trimethylhydroquinone, 3,5-diethyl-2-hydroxyhydroquinone, and 3,5-diethyl-1,2,4-trimethoxybenzene with dichloromaleic or citraconic anhydride in an AlCl3—NaCl melt is accompanied by o-C-dealkylation to afford functionally substituted naphthazarins. 相似文献
39.
40.
Satish N. DigheHemant R. Jadhav 《Tetrahedron letters》2012,53(43):5803-5806
Microwave assisted simple, rapid, solventless, and catalyst-free chemoselective method for the protection of amino group in aromatic, aliphatic, heterocyclic, aralkyl amines, phenyl hydrazine, and amino acid esters in good to excellent isolated yield (83-98%) in short reaction time (2-12 min) has been reported. 相似文献