concentration with optimized electrical transport properties were achieved in La2CuO4-based thermoelectric oxides. Results showed that Ba has the best doping effect among the three dopants, with an optimal carrier concentration of ∼1020 cm−3. Furthermore, the figure of merit (ZT) value was enhanced over the entire temperature range with a maximum ZTave of ∼0.03 at 300–923 K, which is nearly two orders of
与传统的热电半导体相比,具有高温热稳定性的热电氧化物的研究进展远远落后。本工作采用高能球磨、固相反应和放电等离子烧结相结合的方法合成了层状氧化铜La 2 CuO 4 。通过在La位置引入金属元素(Ba、Sr、Pb),在La 2 CuO 4基热电氧化物中实现了载流子浓度的增加和电传输性能的优化。结果表明,Ba在三种掺杂剂中掺杂效果最好,最佳载流子浓度为~ 10 20 cm -3。此外,品质因数(ZT) 值在整个温度范围内都有所提高,在 300-923 K 时最大ZT ave约为 0.03,比 printine La 2 CuO 4高出近两个数量级。我们的研究成功地开发了La 2 CuO 4基氧化物的热电性能,具有成为飞机关键部件高温检测热电偶的巨大潜力。
Lewis Acid-Catalyzed 1,4-Addition and Annulation of 4-Hydroxy-coumarins with <i>o</i>-Hydroxyphenyl Propargyl Amines: Entry to Regio-Selective Synthesis of Furano[3,2-<i>c</i>]coumarins and Pyrano[3,2-<i>c</i>]coumarins
作者:Ganesh Shivayogappa Sorabad、Ding-Yah Yang
DOI:10.1021/acs.joc.3c00213
日期:——
furano[3,2-c]coumarin and pyrano[3,2-c]coumarin derivatives is reported. The reaction presumably proceeds by the conjugate addition of 4-hydroxycoumarin to the in situ-generated alkynyl o-quinone methide and is followed by intramolecular 5-exo-dig and 6-endo-dig annulation to form furano[3,2-c]coumarins and pyrano[3,2-c]coumarins, respectively. The prepared o-hydroxyl substituted pyrano[3,2-c]coumarins
报道了邻羟基苯基炔丙基胺与 4-羟基香豆素的简单区域选择性路易斯酸催化级联环化反应,得到呋喃并[3,2- c ]香豆素和吡喃并[3,2- c ]香豆素衍生物。该反应可能是通过将 4-羟基香豆素与原位生成的炔基o-醌甲基化物共轭加成,然后进行分子内 5- exo-dig和 6- endo-dig环化形成呋喃并 [3,2- c ]香豆素和吡喃[3,2- c ]香豆素。制备的邻羟基取代的吡喃并[3,2- c]香豆素可以很容易地通过酸介导的环化作用转化为相应的香豆素衍生的双氧杂环化合物。
A mild efficient iodine-catalyzed synthesis of novel anticoagulants with 2,8-dioxabicyclo[3.3.1]nonane core
作者:Nemai C. Ganguly、Pallab Mondal、Sushmita Roy
DOI:10.1016/j.tetlet.2013.02.092
日期:2013.5
An efficient coupling of 2-hydroxychalcones/alpha,beta-enones with 4-hydroxycoumarin/5,5-dimethylcyclohexyl-1,3-dione (dimedone) has been accomplished to provide access to a novel class of potential anticoagulants with 2,8-dioxabicyclo[3.3.1]nonane core. The reaction proceeds by Michael-bicycloketalization sequence under iodine catalysis (10 mol %) in aqueous ethanol under reflux. Good to excellent yields, impressive selectivity, absence of byproduct formation, avoidance of toxic organic solvents, and utilization of metal-free water-compatible mild Lewis acid catalyst are the key attractive features of this protocol. (C) 2013 Elsevier Ltd. All rights reserved.
A bio-inspired synthesis of hybrid flavonoids from 2-hydroxychalcone driven by visible light
deliver structurally diverse hybrid flavonoids in good to excellent yields in the presence of a catalytic Brønsted acid. Moreover, moderate enantioselectivities could be obtained using a catalytic chiral phosphoric acid via counter anion directed addition. Based on mechanistic studies, the reaction is proposed to proceed via tandem double-bond isomerization/dehydratedcyclization of 2-hydroxychalcone
描述了一种由 2-羟基查耳酮合成的杂合类黄酮的仿生合成。在 24 W CFL 的照射下,2-羟基查耳酮与各种亲核试剂反应,在催化布朗斯台德酸存在下以良好至优异的产率提供结构多样的杂化黄酮类化合物。此外,使用催化手性磷酸通过反阴离子定向加成可以获得中等的对映选择性。基于机理研究,该反应被提议通过2-羟基查耳酮的串联双键异构化/脱水环化形成瞬时黄鎓阳离子,该阳离子被亲核试剂原位捕获以提供杂化黄酮类化合物。