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糠醛经过簡单处理即能咸为糠酸(2-呋喃甲酸)。由于糠酸及其衍生物用途众多,因此,在国际呋哺化学会議已确定糠酸为露要商品之一。 (一) 糠酸的制备它从糠醛制取方法有二。 (1) 以氫氧化鈉与糠醛进行康尼柴罗反应后得糠酸鈉和糠醇,将所生成的糠酸鈉进行酸化即生成糠酸。 相似文献
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以糠酸、甲醇、氢气为原料,采用连续流动固定床微反应器,Pd-Ni/γ-Al2O3为催化剂,使糠酸一步加氢甲酯化生成α-四氢糠酸甲酯.研究了反应的温度,压力,气、液体流速,进料流量等因素对催化反应的影响.结果表明:在1.5MPa,250℃,氢气空速3300 h-1,液体空速3.0 h-1(氢油比为50)时,糠酸转化率为96.6%,四氢糠酸甲酯的选择性97.2.0%,产率94.0%.催化剂稳定性较好,连续运转280小时后未见活性下降.该反应体系活性高,选择性好,反应压力低,催化剂性能稳定,操作简单,产物易分离. 相似文献
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高效液相色谱法测定银杏外种皮中银杏酸的含量 总被引:20,自引:3,他引:20
建立了反相高效液相色谱法测定银杏外种皮中银杏酸含量的方法,色谱柱为Inertsil ODS-2,流动相为甲醇-3%Hac溶液(92:8,V/V),流速1.0mL/min;柱温40℃;紫外检测波长310nm;线性范围:0.572-10.30цg(相关系数R=0.9999);检测限5.2ng(3a)。银杏外种皮提取物经一步硅胶柱层析预处理。实验测得银杏外种皮中银杏酸含量为5.46%;平均回收率为97.5%,RSD为1.9%(n=6)。该方法简便、准确、线性范围宽。 相似文献
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反相离子对色谱法测定牛奶与奶粉中糠氨酸的含量 总被引:1,自引:0,他引:1
建立了反相离子对色谱法测定牛奶和奶粉中糠氨酸含量的分析方法。样品的盐酸水解液经氮气吹干,流动相溶解定容后直接测定。实验条件为:Luna C18色谱柱,柱温30℃,以2.5mmol/L 1-庚烷磺酸钠(磷酸调pH2.2)-乙醇(体积比为88∶12)为流动相,检测波长为280nm,流速为1mL/min。结果表明,糠氨酸的质量浓度在0.5~75.0mg/L范围内与其峰面积呈良好的线性关系,线性方程为y=49365x+10677(r=0.9999),检出限(S/N=3)为0.0065mg/L。牛奶和奶粉样品的RSD分别为0.3%和1.0%,平均加标回收率均为98%。该方法在样品预处理中省去了干过滤及C18柱预萃取过程,操作简便,成本低廉,适用于乳品中糠氨酸含量的测定。 相似文献
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建立了分离和测定荆花胃康原料药和胶丸中的主要成分对-异丙基甲苯(ρ-cymene)和α-萜品烯(α-Terpinene)的反相高效液相色谱梯度洗脱的方法.采用Spherisorb ODS1分析柱;甲醇-水梯度洗脱:0~15 min(V(甲醇):V(水)=75:25),15~22 min(V(甲醇):V(水)=85:15),22~28 min(V(甲醇):V(水)=75:25);紫外检测波长220 nm.对-异丙基甲苯在2.0~6.0 mg/mL,α-萜品烯在4.0~12.0 mg/mL范围内,峰面积与其质量浓度呈良好的线性关系;平均加样回收率对-异丙基甲苯为99.6%(RSD=1.3%),α-萜品烯为98.2%(RSD=1.1%).该方法灵敏度高,重现性好,结果稳定,可用于同时测定荆花胃康原料药及胶丸中的对-异丙基甲苯和α-萜品烯. 相似文献
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《催化学报》2017,(7)
设计开发绿色、可持续的生物质资源高效转化制化学品催化过程具有重要的科学与应用研究价值.生物质基平台分子糠醛在分子氧存在下与甲醇发生氧化酯化,提供了一条糠酸甲酯的"非石油基"合成新路线.该反应采用贵金属/非贵金属催化体系,目前通常需要引入K_2CO_3或CH_3ONa等碱性添加剂,以提高催化氧化酯化反应活性和选择性;但是存在活性组分流失、生成副产物及污染环境等问题,阻碍了其进一步应用.探索高性能非贵金属催化剂,实现无碱条件下糠醛高效氧化酯化,对于提高该生物质路线竞争力与推动工业化进程具有重要意义.本文利用浸渍法将1,10-邻菲罗啉合钴(Ⅱ)负载到碱性载体氧化镁上,在氮气气氛下800 ℃热解,制备了非贵金属Co-N-C/MgO催化剂.在糠醛氧化酯化制糠酸甲酯反应中,Co-N-C/MgO催化剂表现出优异的性能,在0.5 MPa O_2,100 ℃条件下反应12 h,糠醛转化率达到93.0%,糠酸甲酯选择性达到98.5%,远超过相同方法制备的其他载体(活性炭、NaX、NaY和CaO)负载的钴基催化剂,实现了无碱性添加剂条件下糠醛高效氧化酯化制糠酸甲酯.X射线光电子能谱、X射线衍射、透射电镜、元素分析以及对比实验结果表明,Co-N-C/MgO催化剂上可能存在含钴的氮掺杂碳物种;该催化剂在糠醛氧化酯化中的高性能与其脱氢能力密切相关.并且在0.3–1.0 MPa氧气压力范围内,Co-N-C/MgO催化糠醛氧化酯化过程基本不受压力变化影响.糠醛与甲醇的氧化酯化反应和缩合反应为两个竞争路径,反应路径决定了反应的主要产物.我们使用盐酸处理Co-N-C/MgO催化剂,脱除MgO载体,制备了Co-N-C(HCl)催化剂.当使用该催化剂时,糠醛与甲醇主要发生缩合反应,得到缩醛产物2-(二甲氧基甲基)呋喃.如果在Co-N-C(HCl)催化反应体系中引入MgO添加剂,则主要发生糠醛氧化酯化反应,主产物为糠酸甲酯.为了验证-Cl是否对反应产生影响,使用NaCl溶液对Co-N-C/MgO进行浸渍、清洗处理,或直接使用NaCl为添加剂-;在这两种情况下,糠醛转化率与糠酸甲酯选择性均下降,表明Cl对糠醛氧化酯化反应具有负面作用.根据实验结果,阴离子-(Cl)可能与℃(Ⅱ)中心发生配位,从而影响了金属活性中心的催化性能.Co-N-C(HCl)加入氧化镁,使得糠醛主要遵循氧化酯化路径进行转化,降低-Cl对Co-N-C(HCl)催化活性中心的影响.以上研究可为生物质基醛类化合物氧化酯化转化过程以及高性能非贵金属催化剂的设计开发提供有益参考. 相似文献
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生物质衍生物糠醛还原胺化是合成糠胺的一种有效方法。本文以糠醛为原料、氨水为氨源,使用商业Raney Ni催化糠醛还原胺化合成糠胺,考察了氢压、温度、n(糠醛)/n(氨水)、溶剂、催化剂用量等条件对反应的影响。实验结果表明:在1,4-二氧六环溶剂中,0.03 g Raney Ni、n(糠醛)/n(氨水)=1/2、130 ℃、2.0 MPa H2条件下反应3 h,糠醛转化率100%,糠胺选择性96.3%。与传统方法相比,该工艺实现了非贵金属催化剂作用下高选择性反应,具有操作简单、低成本、收率高等优点。
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以水为萃取剂,建立了变压器油中糠酸含量的反相液液微萃取/高效液相色谱测定方法。通过研究萃取剂的p H值、萃取剂体积、稀释剂用量、萃取时间及离心转速的影响,确定了最优的萃取条件。结果表明:在以中性水为萃取剂,萃取剂体积为150μL,稀释剂比例V油∶V正己烷为3∶1,涡旋萃取时间为5 min,离心转速为5 500 r/min的条件下,水萃取相直接用于高效液相色谱测定,变压器油中糠酸的浓度在0.05~5.00 mg·L-1范围内呈良好线性,相关系数(r)为0.999 9,方法的检出限为9.6μg·L-1,相对标准偏差(RSD,n=6)为1.4%,糠酸的富集倍数为13.6倍。实际老化样品测定的加标回收率为99.7%~105.1%,并对样品中的糠酸进行了HPLC-MS定性分析。该方法简捷有效,为变压器油纸绝缘老化特征量的研究提供了数据支持。 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
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The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
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In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates. 相似文献
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An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions. 相似文献
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An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction. 相似文献
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Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described. 相似文献
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The Diels-Alder reactivity of 1,2-heteroborines (H4C4B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed. 相似文献
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Xi-Liu YunWen-Ying Bi Jian-Hui HuangYu Liu Daisy Zhang-NegrerieYun-Fei Du Kang Zhao 《Tetrahedron letters》2012,53(38):5076-5080
A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd2(dba)3-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring. 相似文献