薤白挥发油成分的超临界CO2萃取及GC-MS分析

采取超临界CO2萃取和水蒸气蒸馏两种方法提取薤白中的挥发油,比较了两种提取方法得到的挥发油的理化性质,并利用GC-MS对它们进行了定性、定量分析。两种方法的主要提取物均为含硫化合物,但超临界CO2萃取法得到的含硫化合物的数量和质量都高于水蒸气蒸馏法得到的提取物。采用水蒸气蒸馏法提取8 h得到的萃取率为1.72%。通过设计的超临界CO2萃取的正交实验,得到了最佳萃取工艺条件为:压力25 MPa,温度40℃,CO2流量为25L/h。最佳萃取时间为120 min,萃取率为4.41%,是水蒸气蒸馏法萃取率的2.8倍。实验结果表明,超临界CO2萃取法简单易行,可以较快速、有效地提取薤白中的挥发油。     

超临界CO2流体萃取辛夷精油的组分分析

采用超临界CO2流体萃取辛夷精油,萃取率为3．8％,比水蒸气蒸馏的萃取率高58％。利用气相色谱-质谱联用(GC-MC)法对辛夷精油进行组分的定性和定量分析,并与水蒸气蒸馏法所得辛夷精油的组分相比较,发现超临界CO2流体萃取所得辛夷精油的香气、品质、产率优于水蒸气蒸馏法所得辛夷精油。     

超临界CO2流体萃取法与水蒸气蒸馏法提取荆芥穗挥发油化学成分的研究

采用超临界CO2萃取法(SFE)与水蒸气蒸馏法(SD)从荆芥穗中提取挥发油。采用SE-54毛细管柱进行分析,用气相色谱-质谱法对挥发油中各种化学成分进行鉴定,用归一化法测定各组分的含量。色谱条件:SE-54毛细管柱 (30 m×0.25 mm i.d.,0.25 μm),柱温50 ℃(3 min)5 ℃/min180 ℃(2 min)10 ℃/min260 ℃(50 min);分流进样,分流比1∶50;进样口温度280 ℃。在采用超临界CO2萃取法提取的挥发油中共鉴定出54种成分,其主要成分为长叶薄荷酮、薄荷酮、亚油酸氯化物等;在水蒸气蒸馏法提取的挥发油中共鉴定出39种成分,其主要成分为长叶薄荷酮、薄荷酮、柠檬烯等。超临界法较水蒸气法更加稳定可靠,重现性好,适用于中药挥发油的化学成分分析。     

超临界流体萃取技术在提取中药挥发油中的应用

用超监介CO2流体萃取技术对多种中药挥发油的提取进行了综述,并将其与传统的水蒸馏法进行比较。结果表明,用超临界流体法不仅挥发油的收率高,而且提取时间也大大缩短。     

超临界流体萃取气相色谱法测定鱼肉中的毒死蜱残留

建立了利用离线超临界CO2萃取气相色谱(SFE-GC)测定鱼肌肉中毒死蜱残留量的分析方法。超临界CO2萃取鱼肌肉中毒死蜱的适宜条件为：温度100℃,压力41．370MPa,CO2流量为1mL／min,动态萃取30min,静态萃取时间15min,调节剂甲醇(添加量0．5mL),收集液丙酮。最小检出量为0．01ng;添加回收率为77.3％～105．1％;相对标准偏差(RSD)为2．4％～15．4％,符合残留分析要求。全程分析时间小于2h。     

超临界CO2萃取波棱瓜种子油及脂肪酸的气相色谱-质谱分析

利用超临界CO2萃取藏药波棱瓜种子油,并对种子油进行了气相色谱-质谱分析.实验确定的最佳超临界萃取的条件是:萃取温度45℃,萃取压力为20 MPa,CO2流量为35~40 kg/h,提取时间为120 min,在此条件下波棱瓜种子油的提取率为33.35%.利用气相色谱-质谱对种子油分析,结果发现其主要含有各类不饱和脂肪酸,其中亚麻酸、亚油酸、油酸的相对含量分别为:12.271%、20.149%和52.282%.通过对波棱瓜种子油的分析研究为其进一步开发利用提供了科学依据.     

不同提取方法对赤芍挥发性成分及抗氧化活性的影响

比较了超临界CO_2萃取和水蒸气蒸馏技术对野生赤芍挥发油提取的效率;用气相色谱-质谱联用技术对两种挥发油进行成分分析和化学成分的比较;比较了两种挥发油对DPPH·和超氧负离子自由基的清除作用.     

肉桂挥发油的超临界CO2萃取法与水蒸气蒸馏法提取的比较分析

采用超临界CO2萃取法与水蒸气蒸馏法从肉桂中提取挥发油,用GC-MS法测定其化学成分和相对含量,对两种提取方法所得的挥发油进行比较,水蒸气蒸馏提取肉桂挥发油的产率为1％(ω),主要成分为肉桂醛、α-芹子烯、α-（王古）Ba烯、δ-杜松烯;超临界CO2萃取法提取的产率为1．5％(W),主要成分为肉桂醛、α-玷圯烯、α-依兰油烯、δ-杜松烯等。     

超临界CO_2萃取-分子蒸馏对白术挥发油的提取分离和GC-MS分析

用超临界CO2萃取技术提取白术挥发油，然后用分子蒸馏对所得的萃取物进行精分离，得到蒸出物；超临界萃取物收率为2．42％(w)，分子蒸馏蒸出物收率26．3％(w)；对超临界萃取物和分子蒸馏蒸出物分别进行GC—MS分析，结果超临界萃取物检测出33个化合物，分子蒸馏蒸出物检测出27个化合物，主要成分均为2，7-二甲氧基-3，6-二甲基萘、γ-芹子烯、大根香叶烯等，但相对含量有区别。     

不同提取方法对蜘蛛香挥发油的研究

考察微波辅助萃取法和水蒸气蒸馏法对提取蜘蛛香挥发油化学成分的影响。分别采用微波辅助萃取法和水蒸气蒸馏法提取蜘蛛香挥发油,并用气相色谱质谱联用(GC-MS)对所提取的挥发油化学成分进行分析。微波辅助萃取法和水蒸气蒸馏法制得的蜘蛛香挥油化学成分有一定的差别。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

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.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

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%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

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.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

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.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

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.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

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.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.