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91.
92.
采用沉淀法和浸渍法制备了2种铬基(Cr2O3和CrO3/Cr2O3)催化剂,用于气相氟化2-氯-1,1,1-三氟乙烷合成1,1,1,2-四氟乙烷。研究发现含有低价铬(Cr3+)物种的Cr2O3催化剂上2-氯-1,1,1-三氟乙烷的稳态转化率为18.5%,而含有高价铬(Cr6+)物种和低价铬(Cr3+)物种的CrO3/Cr2O3催化剂初始转化率达到30.6%,然而存在明显的失活。含有Cr6+物种的CrO3/Cr2O3催化剂的2-氯-1,1,1-三氟乙烷氟化反应初始TOF值为1.71×10-4 molHCFC-133a·molCr(Ⅵ)-1·s-1,高于含有Cr3+物种的Cr2O3催化剂(4.16×10-5 molHCFC-133a·molCr(Ⅲ)-1·s-1)。Cr2O3催化剂在氟化反应前后催化剂的物相结构保持不变;而含有高价铬物种的CrO3/Cr2O3催化剂经HF反应后生成了CrOxFy活性物种。然而,CrOxFy物种在反应中挥发或转化成稳定但无活性的CrF3,从而导致催化剂失活。 相似文献
93.
M. B. Deshmukh S. D. Jadhav A. R. Mali A. W. Suryawanshi P. V. Anbhule S. S. Jagtap 《合成通讯》2013,43(23):2967-2971
The conjugate addition of organomanganese reagents to α,β‐unsaturated aldehydes and allylic bisacetate in presence of Me3Si‐Cl and tetrakis acetonitrile copper(I) tetrafluroborate is described. 相似文献
94.
A general and efficient synthetic method of 1,3-bis(phenylseleno)-2-propanol by reducing diphenyl diselenides with sodium borohydride in basic environment and then reacting with epichlorohydrin are described. 相似文献
95.
A convenient, five‐step preparation of 2‐acetyl‐4,5‐difluorothiophene from 2,3‐dibromothiophene is described. 相似文献
96.
An efficient method for the synthesis of valuable N-, O-, and Si-containing 1Z,5Z-diene compounds was developed. The method comprises Cp2TiCl2-catalyzed homo- and cross-cyclomagnesiation of 1,2-dienes by Grignard reagents (RMgR′) to give 2,5-dialkylidenemagnesacyclopentanes in up to 96% yield. This approach was successfully used in the synthesis of 5Z,9Z-dienoic acids, precursors of acetogenins and insect pheromones. 相似文献
97.
98.
The brief review of industrial technologies of titanium-containing concentrates processing has been carried out. Drawbacks of the existing titanium manufacture schemes are shown and the necessity of the essentially new fluoride technologies development has been proved. The reactions proceeding during the fluorination of rutile concentrate with element fluoride are described in the given work. The thermodynamic research of the process has been carried using ASTRA software. Dependence of mass concentration change of titanium tetrafluoride has been investigated in products of reaction on the temperature of the process, and the choice of optimum excess of fluoride has been proved. 相似文献
99.
Maximilian Stangier Alexej Scheremetjew Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201654
Electrochemical fluorinations of C(sp3)−H bonds with a nucleophilic fluoride source have been accomplished in a chemo- and site-selective fashion, avoiding the use of electrophilic F+ sources and stoichiometric oxidants. The introduced metal-free strategy exhibits high functional group tolerance, setting the stage for late-stage fluorinations of biorelevant motifs. The synthetic utility of the C(sp3)−H fluorination was reflected by subsequent one-pot arylation of the generated benzylic fluorides. 相似文献
100.
Dr. Huaiyuan Zhang Prof. Dr. Thomas Wirth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(21):e202200181
Xanthene derivatives have broad applications in medicines, fluorescent probes, dyes, food additives, etc. Therefore, much attention was focused on developing the synthetic methods to prepare these compounds. Binaphthyl-based xanthene derivatives were prepared through the oxidation of BINOLs promoted by the hypervalent iodine reagent iodosylbenzene (PhIO). Nine-membered lactones were obtained through a similar oxidative reaction when iodoxybenzene (PhIO2) was used. Additionally, one-pot reactions of BINOLs, PhIO and nucleophiles such as alcohols and amines were also investigated to provide alkoxylated products and amides in good to excellent yields. 相似文献