Picolinyl group as an efficient alcohol protecting group: cleavage with Zn(OAc)2·2H2O under a neutral condition
摘要:
As an efficient alcohol protecting group, picolinates (Pic), prepared from the corresponding alcohols using commercial picolinoyl chloride, are readily cleaved by Zn(OAc)(2) or Cu(OAc)(2), even in the presence of other common alcohol protecting groups. Moreover, the picolinyl group at C-2 position in carbohydrates can be selectively cleaved to give methyl 4,6-O-benzylidene-3-O-picolinyl-alpha-D-glucopyranoside and 3-O-picolinyl methyl-4,6-O-benzylidene-alpha-D-galactopyranoside in good yields. (c) 2005 Elsevier Ltd. All rights reserved.
The ubiquitousness of esters and amide functionalities makes their coupling reaction one of the most sought-after organic transformations. Herein, we have described an efficient microwave-assisted synthesis of esters and amides. Soluble triphenylphosphine, in conjugation with molecular iodine, gave the desired products without the requirement for a base/catalyst. In addition, a solid-phase synthetic
Esterification of free fatty acids (Biodiesel) using nano sulfated-titania as catalyst in solvent-free conditions
作者:Mona Hosseini-Sarvari、Esmat Sodagar
DOI:10.1016/j.crci.2012.10.016
日期:2013.3
Résumé Nano sulfated titania was tested as catalyst for esterification of free fatty acids, specially methanolic and ethanolic esterification of stearic acid (biodiesels). Factorial design evidenced a positive effect of reaction temperature, amount of catalyst, and solvents on ester conversion. This nano-sized sulfated titania has been prepared by a sol-gel hydrothermal process. This prepared sulfated titania showed high catalytic activity in direct esterification of fatty acids as well as benzoic acids with various alcohols and phenols under solvent-free conditions. This method is of great value because of its environmentally benign character, easy handling, high yields, convenient operation, and green. FT-IR studies are shown that the catalyst can be reused for acylation without loss of catalytic activity.
Homarine Alkyl Ester Derivatives as Promising Acetylcholinesterase Inhibitors
作者:Karen G. João、Romeu A. Videira、Fátima Paiva‐Martins、Patrícia Valentão、David M. Pereira、Paula B. Andrade
DOI:10.1002/cmdc.202100265
日期:2021.11.5
Restoring cholinergic activity: Alkyl esters of homarine were synthesized and their potential to inhibit AChE was screened using E. electricus AChE and rat brain AChE. The effects on fluorescence emission of AChE tryptophan residues were also evaluated revealing that all compounds can interact with the tryptophan residues in the AChE catalytic pocket. HO−C16 was the most potent molecule, with Ki=18
恢复胆碱能活性:合成了人参烷基酯,并使用 E.electricus AChE 和大鼠脑 AChE筛选了它们抑制 AChE 的潜力。还评估了 AChE 色氨酸残基对荧光发射的影响,表明所有化合物都可以与 AChE 催化袋中的色氨酸残基相互作用。HO-C 16是最有效的分子,K i =18.96 μM,K d =36.45 μM。
CeO2-catalysed one-pot selective synthesis of esters from nitriles and alcohols
were tested for one-pot selective synthesis of esters fromnitriles and alcohols. Ceria (CeO2) showed more than two orders of magnitude higher activity than the other oxides. CeO2 acted as a reusable and effective catalyst for the ester synthesisfrom various nitriles and alcohols under neutral and solvent-free conditions at 160 °C. This method provides a rare example for the synthesis of heteroaromatic
Nanocrystalline CeO<sub>2</sub> as a Highly Active and Selective Catalyst for the Dehydration of Aldoximes to Nitriles and One-Pot Synthesis of Amides and Esters
作者:Anastasia Rapeyko、Maria J. Climent、Avelino Corma、Patricia Concepción、Sara Iborra
DOI:10.1021/acscatal.6b00272
日期:2016.7.1
The dehydration of aldoximes into nitriles has been performed in the presence of various metal oxides with different acid–base properties (Al2O3, TiO2, CeO2, MgO). The results showed that a nanocrystalline CeO2 was the most active catalyst. An in situ IR spectroscopy study supports a polar elimination mechanism in the dehydration of aldoxime on metal oxide catalysts, in which Lewis acid sites and basic
在具有不同酸碱性质的各种金属氧化物(Al 2 O 3,TiO 2,CeO 2, MgO)存在下,醛肟肟脱水成腈。结果表明,纳米晶CeO 2是活性最高的催化剂。原位红外光谱研究支持醛肟在金属氧化物催化剂上脱水的极性消除机制,其中涉及路易斯酸位和碱性位。路易斯酸位点干预肟在催化剂表面的吸附,而表面碱位点负责C1-H键的裂解。因此,纳米晶CeO 2的酸碱性质负责高催化活性和选择性。使用纳米级二氧化铈以良好的收率(80-97%)将各种醛肟(包括烷基醛和环烷基醛肟)脱水成相应的腈,从而得到稳定且可重复使用的催化剂。另外,已经表明,使用纳米二氧化铈作为催化剂,通过一锅法可以从2-吡啶并肟中以高收率获得各种药理上重要的产物,例如吡啶甲酸酰胺和吡啶甲酸烷基酯衍生物。