TS-1/H_2O_2体系催化香茅醛肟化反应

将TS-1/H2O2催化体系用于催化香茅醛氨肟化制备香茅醛肟反应中,结果表明,在优化的反应条件下,香茅醛转化率和香茅醛肟选择性分别达99.9%和99.2%以上.反应过程中主要存在两对竞争反应:TS-1催化的醛肟化反应和碱催化的羟醛缩合反应;TS-1催化的醛肟化反应和双键环氧反应.通过调节体系中氨含量可有效抑制副反应.     

2-(2′-乙氧羰基乙基)香茅醛的分子内烯反应

R( )-香茅醛的烯胺与丙烯酸乙酯反应,得2-(2′-乙氧羰基乙基)香茅醛。此产物用 Lewis 酸进行分子内烯反应,水解和内酯化后,得一由四个异构体组成的粗产物。此异构体的比例随反应条件和所用的 Lewis 酸不同而变化。经一系列反应,由此烯反应产物可得二个不同的酮-γ-内酯化合物,它们可望用作合成青蒿素类似物的中间体。其中一个γ-内酯8b 证明与一青蒿素降解产物一致,因此也就确定了它的立体化学。     

水溶性钯配合物催化柠檬醛的选择加氢反应研究：I.反应条件的影响

研究了在水／有机物两相体系中水溶性钯－膦配合物催化柠檬酸的加氢反应。考察了反应温度、氢气压力、底物和催化剂浓度、反应时间、水相ｐＨ值等对该反应的影响，并与几种柠檬醛衍生物的加氢结果进行了比较。发现仅用蒸馏水作水相，则主要产物是二氢香茅醛（〉９３％）；而水相水加入Ｎａ２ＣＯ３后，则主要产物为香茅醛（９７％），且加氢速度比同样条件下使用Ｐｄ／Ｃ催化剂快得多。     

柠檬醛的非均相催化氢化：二氢香茅醛的制备

对含有多个可被还原的官能团化合物的催化氢化,难以找到既有高活性又具有高度选择性的催化剂。柠檬醛分子中含有两个碳碳双键和一个醛基,随氢化条件的不同可能生成下列4种产物:     

离子液体介质中用Cu/ZrO2-SiO2催化香茅醛加氢合成薄荷醇

制备了Cu/ZrO2-SiO2双载体催化剂, 并在离子液体介质中研究了香茅醛催化加氢合成薄荷醇的反应. 研究结果表明, 离子液体中的阳离子与香茅醛分子中的羰基形成氢键, 使香茅醛更容易异构化为胡异薄荷醇, 提高了催化剂的选择性; 特别是可调节酸度的[bmim][AlmCln]离子液体, 有效地提供了香茅醛的异构化所需要的路易斯酸条件, 在竞争性加氢中促进了香茅醛向生成薄荷醇的方向转化. 在0.8 MPa, 90 ℃, 2 h的条件下, 香茅醛一锅反应生成薄荷醇的转化率为100%, 对薄荷醇的选择性为91.3%, 而且, 催化剂和离子液体可回收和重复使用.     

不饱和醛的新合成法

不饱和醛的新合成法史真，顾焕（西北大学化学系，西安７１００６９）不饱和醛是一类结构特殊的醛，常由醛缩合或不饱和醇氧化制得。本文在研究咪唑啉还原反应的基础上，提出了不饱和醛的一种未见文献报道的合成方法。这一新合成方法，突破了传统的制备方法，以不饱和羧酸...     

基于氢键诱导理论的有机化学探索实验：(+/-)-2-亚甲基香茅醛的合成与快速鉴定

本实验用吡咯烷和4-二甲基氨基苯甲酸作为有机小分子催化剂，催化天然香料(+/-)-香茅醛与甲醛的Aldol缩合反应并脱水合成(+/-)-2-亚甲基香茅醛。基于小分子催化的氢键诱导效应，我们选用二氯甲烷、四氢呋喃、无水乙醇三种溶剂进行平行反应，用薄层色谱法监控平行反应的转化速度，筛选相对最佳反应溶剂。同时，我们用共振离域理论解释原料和产物在核磁共振化学位移、薄层色谱比移值、液相色谱保留时间的差异。本实验弥补了有机化学实验在反应条件优化方面的空白。     

醚取代芳香β－醛酮衍生物的合成及抗菌活性研究

鱼腥草素具广谱的抗菌活性,其药效团为β－醛酮结构。本文以对羟基苯乙酮为原料,通过Claisen缩合、加成、缩合得到12个芳香β－醛酮衍生物,所合成化合物经过红外、核磁、质谱进行了结构表征。对所合成的化合物进行了抑菌活性测试,初步构效关系表明,烷氧基胺席夫碱可能是活性基团,酮羰基的存在对提高抗菌活性有利,苯环上取代基对抗菌活性有重要影响。     

取代苯基吡唑醛缩邻氨基苯酚Schiff碱的合成与表征

取代苯肼与乙酰丙酮经过缩合反应合成取代苯基吡唑．取代苯基吡唑在Vilsmeier—Haak反应条件下,得到取代苯基吡唑醛．取代苯基吡唑醛与邻氨基苯酚作用生成取代苯基吡唑醛缩邻氨基酚Schiff碱．这些化合物的结构经IR光谱、质谱和^1H NMR确认．     

Studies on catalytic hydrogenation of citral by water-soluble palladium complex

The hydrogenation of citral has been studied in biphasic system using water-soluble PdCl₂(TPPTS)₂ as catalyst. The selectivity to form citronellal increased with increasing pH values of the aqueous phase. At the same pH value, the selectivity was higher when the hydrogenation was carried out in the presence of Na₂CO₃ than in the presence of NaOH. The main product was citronellal and a maximum yield of 93% had been obtained using Na₂CO₃ solution at pH 11.6. The CC bond in citronellal could be further hydrogenated to form dihydrocitronellal when the hydrogenation was carried out in distilled water at pH 6.0. The yield of dihydrocitronellal could reach 93% with prolonged reaction time to 6 h. Therefore, high yields of either citronellal or dihydrocitronellal could be obtained from citral by selecting the corresponding reaction conditions.     

水溶性钯配合物催化柠檬醛的选择加氢反应研究 Ⅰ.反应条件的影响

研究了在水／有机物两相体系中水溶性钯－膦配合物催化柠檬醛的加氢反应．考察了反应温度、氢气压力、底物和催化剂浓度、反应时间、水相ｐＨ值等对该反应的影响，并与几种柠檬醛衍生物的加氢结果进行了比较．发现仅用蒸馏水作水相，则主要产物是二氢香茅醛（＞９３％）；而水相中加入Ｎａ２ＣＯ３后，则主要产物为香茅醛（９７％），且加氢速度比同样条件下使用Ｐｄ／Ｃ催化剂快得多．     

Terpenes to Ionic Liquids: Synthesis and Characterization of Citronellal-Based Chiral Ionic Liquids

A series of new chiral ionic liquids have been prepared and characterized starting from a simple, economical, and commercially available monoterpene, citronellal. The aldehyde functionality in citronellal is converted into a Schiff base using an amine, followed by reduction with Raney nickel to give the desired quaternary amine. Most of the ionic liquids generated using this procedure are found to be liquids at room temperature.     

Analysis of fragrances in cosmetics by gas chromatography–mass spectrometry

A gas chromatographic (GC)-mass spectrometric (GC-MS) method has been developed for the routine analysis of 11 fragrance substances in cosmetics: cinnamic alcohol, cinnamic aldehyde, eugenol, hydroxy citronellal, α-amyl cinnamic aldehyde, geraniol, isoeugenol, coumarin, dihydrocoumarin, citronellal and citral. Methods for sample preparation of various types of cosmetic products, prior to GC analysis, have also been developed and proved to be rugged. Detection limits of all of target fragrance substances were approximately 1 ppm. Calibration curves of the target fragrance substances analyzed by GC were found to be linear in the investigated concentration range, 0.005% – 0.50%. The recoveries of the target fragrances from various types of cosmetic products were 80% – 116% and the relative standard deviations of the quantitative analysis of the target fragrance substances were within 5%.     

Selective Hydrogenation of Citral over a Carbon‐titania Composite Supported Palladium Catalyst

A novel carbon‐titania composite material, C/TiO₂, has been prepared by growing carbon nanofibers (CNFs) on TiO₂ surface via methane decomposition using Ni‐Cu as a catalyst. The C/TiO₂ was used for preparing supported palladium catalyst, Pd/C/TiO₂. The support and Pd/C/TiO₂ catalyst were characterized by BET, SEM, XRD and TG‐DTG. Its catalytic performance was evaluated in selective hydrogenation of citral to citronellal, and compared with that of activated carbon supported Pd catalyst. It was found that the Pd/C/TiO₂ catalyst contains 97% of mesopores. And it exhibited 88% of selectivity to citronellal at citral conversion of 90% in citral hydrogenation, which was much higher than that of activated carbon supported Pd catalyst. This result may be attributed to elimination of internal diffusion limitations, which were significant in activated carbon supported Pd catalyst, due to its microporous structure.     

MOFs as multifunctional catalysts: one-pot synthesis of menthol from citronellal over a bifunctional MIL-101 catalyst

A bifunctional MOF catalyst containing coordinatively unsaturated Cr(3+) sites and palladium nanoparticles (Pd@MIL-101) has been used for the cyclization of citronellal to isopulegol and for the one-pot tandem isomerization/hydrogenation of citronellal to menthol. The MOF was found to be stable under the reaction conditions used, and the results obtained indicate that the performance of this bifunctional solid catalyst is comparable with other state-of-the-art materials for the tandem reaction: Full citronellal conversion was attained over Pd@MIL-101 in 18 h, with 86% selectivity to menthols and a diastereoselectivity of 81% to the desired (-)-menthol, while up to 30 h were necessary for attaining similar values over Ir/H-beta under analogous reaction conditions.     

Liquid phase hydrogenation of citral and intermediaries over Ir/TiO2/SiO2 catalysts: Kinetic study

Kinetics of the hydrogenation of citral and its intermediates over Ir/TiO₂/SiO₂ catalysts has been studied. The effect of various parameters such as the initial concentration, H₂ pressure partial, temperature and weight of catalyst were examined. A high selectivity towards unsaturated alcohols using this catalyst was demonstrated. The initial rates increased linearly with the catalyst weight. The reaction rate obeys a kinetics represented by the Langmuir–Hinshelwood model. A single site model suggesting the surface reaction as the rate determining step provided the best fit of the experimental data for the hydrogenation of citral and alcohols (geraniol, nerol and citronellol), while a dual site represent the best kinetics for the hydrogenation of citronellal.     

Biosynthesis of Glycomonoterpenes to Attenuate Quorum Sensing Associated Virulence in Bacteria

The acquisition of multidrug resistance in bacteria has become a bigger threat of late, mainly due to the bacterial signaling phenomenon, quorum sensing (QS). QS, among a population of bacteria, initiates the formation of biofilms and offers myriad advantages to bacteria. Burgeoning antibiotic resistance in biofilm-producing bacteria has motivated efforts toward finding new alternatives to these traditional antimicrobials. In the present study, we report the increased solubility and additional quorum quenching as well as biofilm disruption activity of glyco-derivatives of monoterpenes (citral and citronellal). Glycomonoterpenes of citral and citronellal were synthesized via conjugation of the monoterpenes with glucose by the non-pathogenic yeast Candida bombicola (ATCC 22214). Structural elucidation of newly synthesized glycomonoterpenes showed that one synthesized using citronellal contains three major lactonic forms with molecular weight 492.43, 473.47, and 330.39 Da whereas the one produced using citral has an acidic form with molecular weight 389.33 and 346.23 Da. The glycomonoterpenes were able to individually inhibit QS, mediated through various medium-chain and long-chain N-acyl homoserine lactones (AHLs). These new compounds are interesting additions to the known range of quorum sensing inhibitors (QSIs) and could be further explored for potential clinical applications.     

Fast preparation of dihydrocyclocitral from citronellal under solventless microwave irradiation

Dihydrocyclocitral, a useful reagent in organic synthesis, has been synthesized in high yield and with high stereoselectivity from citronellal under microwave irradiation in two steps, involving acetic anhydride under base catalysis, then p-toluenesulfonic acid adsorbed on silica gel under solventless conditions (80% yield, reaction time 22 min).