固体超强酸催化下的醛酮自身缩合及其溶剂效应的研究

研究了在三种固体超强酸催化下醛(酮)自身的羟醛缩合反应,系统考察了反应时间,催化剂用量等因素对反应的影响,优化了反应条件.同时,对该反应的溶剂效应进行了研究.结果表明,当催化剂用量为2 g/1 mol醛(酮),反应5 h,转化率可达40%,溶剂对该反应有明显的抑制作用.超强酸对各种醛都具有较好的催化活性,其催化醛类化合物自身缩合的转化率都在48%以上,选择性在95%以上,证明固体超强酸对该缩合反应有较好的催化活性和选择性.     

含α—羰醛功能基树脂的合成及其对尿素吸附的研究.Ⅰ

本文在研究醛类化合物与尿素反应的基础上，确定含有α－羰醛基的化合物在ｐＨ７．４，３７℃下对尿素有较高的反应活性。将α－羰醛基引入到苯乙烯－二乙烯苯共聚物骨架上，合成出带有α－羰醛基的树脂。实验结果表明，含α－羰醛功能基的树脂在ｐＨ７．４，３７℃条件下与目前临床使用的氧化淀粉相比，具有更大的吸附潜力。本文还研究了吸附条件对该树脂吸附性能的影响。     

相转移催化(PTC)合成β-[2''-降冰片-5''-烯]α,β不饱和酮、醛类

某些α,β不饱和酮, 醛类化合物具有浓郁的果香, 木香味, 广泛存在于天然的精油, 水果, 蔬菜中, 也是重要的有机合成中间体。β-[2'-降冰片-5'-烯]α,β不饱和酮醛类具有特殊的香韵气息, 可和在化妆品, 烟草, 洗涤剂中。该化合物可用环戊二烯和亲二烯体进行Diels-Alder反应, 再用Claisen-Schmidt反应来合成。本文报道了用相转移催化法合成β-[2'-降冰片-5'-烯]α,β不饱和酮、醛类, 并获得较好的效果。     

顶空固相微萃取原位衍生化气相色谱质谱法测定纺织品中挥发性醛类化合物

采用顶空固相微萃取(SPME)原位衍生化气相色谱/质谱(GC/μ-ECD/MS)法分析了纺织品水萃取溶液的挥发性醛类化合物。实验结果表明,固相萃取纤维上预吸附的衍生化试剂O-(2,3,4,5,6-五氟苄基)羟胺(PFBHA)能与顶空瓶内气体中的醛类化合物反应生成醛肟,在进样口热解吸并经色谱柱分离后,由μ-ECD/MS定性定量检测。该方法不仅能减少试剂消耗,操作简便,而且能克服纺织品水萃取液色素干扰等缺点,提高对产品中醛类有害物质评估准确性。     

基于柱前衍生-高效液相色谱-荧光法检测橙汁中的醛类小分子

醛类化合物是果汁中一类重要的风味物质。本研究以一种新型羟氨类荧光试剂4-羟氨基丁基-7-甲氧基-香豆素(HAMC)为醛类衍生试剂，发展了一种基于硝酮化反应的柱前衍生方法。该方法实现了13种醛类小分子在C18柱上的基线分离且检测限低至0.2 nmol/L。利用该方法结合高效液相色谱-荧光检测(HPLC-FLD)成功从橙汁样品中检测出糠醛、5-羟甲基糠醛、甲醛、乙醛及庚醛。该方法灵敏度高、准确性好且无需固相萃取等复杂前处理，在复杂基质的醛类物质分析中具有良好的应用前景。     

3,6-二取代-5,6-二氢-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑的合成及生物活性

以３－芳基－４－氨基－５－巯基－１,２,４－三唑为原料,在酸催化下与醛类发生分子内的Ｍａｎｎｉｃｈ反应,合成了１４个标题化合物,其结构经元素分析、ＩＲ、＾１ＨＮＭＲ和ＭＳ确证。研究了反应条件。生物活性测定结果表明,部分化合物具有较强的生物活性。     

改进的单滴微萃取法测量血样中的醛类

人体病变往往导致脂质过氧化反应,其终端产物多为小分子羰基化合物,尤其是醛类~([1]).醛类已被认为是氧化压力增强的潜在标志物,以及癌症分子标志物.     

氨水介质中金属锌促进醛的呐偶联反应

传统的呐偶合反应必须在无水有机溶剂条件下, 由金属或金属化合物促进羰基化合物进行呐偶合反应. 曾经报道过金属锌在强碱介质或弱酸介质中, 促进羰基化合物进行水相呐偶合反应. 本文报道一种简便、有效的水相呐偶合反应, 它是在含有少量冠醚的稀氨水溶液中, 使用锌粉促进醛基化合物进行水相呐偶合反应, 其中加入少量的冠醚有助于提高反应的产率, 呐醇产率由63%提高到84%. 然而, 呐偶合反应的产率受到羰基周围环境的立体位阻影响较大, 在此条件下, 锌粉能有效地促进芳香族醛类化合物进行水相呐偶合反应, 得到的呐醇产率高, 但非对映异构体选择性差, 而脂肪族醛类化合物得到的呐醇产率较低, 在同样的条件下, 酮类化合物不能顺利进行呐偶合反应.     

具有共轭体系的酮类烯醇硅醚与全氟碘代烷的反应

应用连二亚硫酸钠的引发，通过全氟碘代烷与醛类，酮类烯醇硅醚的反应，合成α－全氟烷基羰基类化合物的方法。利用该方法，还可以用“一锅法”合成含氟β－二酮类化合物。本文报道了在类似的反应条件下，与苯环或双键共轭的烯醇硅醚和全氟碘代反应的结果。     

手性四氢咪唑衍生物的合成及与醛的反应

用含有C2对称轴的手性1，2－二胺同n-Bu3Sn取代的醛类化合物反应，制得了 具有手性辅助基的烯醇化物等价体。再利用金属交换反应将生成的烯醇负离子同醛 类化合物进行缩合反应，制得具有立体选择性的羟基化合物。     

Chlorination reactions of ephedrines revisited. Stereochemistry and functional groups effect on the reaction mechanisms

The stereochemistry of the chlorination reactions with SOCl₂ of free ephedrine and pseudoephedrine and their hydrochlorides, oxamides and sulfonamides was analyzed. Chlorination of free and hydrochloride erythro isomers occurs with 100% inversion of configuration at C-1 (S_N2 mechanism). Chlorination of oxamides and sulfonamides of erythro isomers occurs with retention of the configuration at C-1, (S_Ni mechanism). Chlorination reactions in all threo isomers and derivatives hydrochlorides, oxamides or sulfonamides gave the same ratio of erythro (40%) and threo isomers (60%) (S_N1 mechanism). Treatment of the isomeric mixture of the chlorodeoxyephedrine and chlorodeoxypseudoephedrine hydrochloride in DMSO with HCl changes the isomeric ratio, increasing the erythro isomer content (65%). Using the erythro ethanolamines it is possible to arrive stereoselectively at the erythro chloroamines if the compound is previously tosylated or converted to the amide, or to the threo chloroamines if the compound is directly chlorinated with SOCl₂.     

Determination of threo and erythro configurations of 3-fluorophenylalanine for verifying stereochemical aspects of recently reported syntheses

Determination of threo and erythro configurations of both diastereoisomers of 3-fluorophenylalanine on the basis of chemical transformation and X-ray analysis has confirmed that the aziridine ring opening reaction gives the threo isomer stereoselectively, whereas the fluorodehydroxylation reaction affords both isomers nonselectively.     

(+)-樟脑亚甲胺α位负碳离子的不对称氧化偶联反应研究

本文研究了(+)-樟脑亚甲胺α位负碳离子的氧化偶联反应, 所得偶联产物经高效液相色谱分析,测定了苏式赤式比,苏式异构体的de.值由^1HNMR测定为20-95%,对影响偶联反应的诸因素:如氧化偶联剂.溶剂.碱等进行了初探.     

Stereoselection in the condensation between ethyl propionate and aldehydes

Ethyl propionate can be converted stereoselectively into geometrical isomers of O-ethyl-O-trimethylsilylmethylketene acetal ($\text{5}$). The E-isomer of $\text{5}$ condenses with aldehydes by titanium tetrachloride to give stereoselectively the threo isomers of ethyl 2-methyl-3-hydroxy carboxylates.     

Stereochemically general approach to adjacent bis(tetrahydrofuran) cores of annonaceous acetogenins

A series of six 2,5-disubstituted adjacent bis(tetrahydrofuran) stereoisomers with trans/erythro/cis, trans/threo/trans, or cis/threo/cis relative stereochemistry have been synthesized from known dihydroxycyclooctenes via ring opening/cross metathesis and Pd(0)-mediated asymmetric double cycloetherification. The stereochemistry of four of these isomers has been found in the biologically active annonaceous acetogenin natural products. [reaction: see text].     

Stereochemistry of heterocycles. XL. Stereochemistry of the synthesis of 2,3-dialkyloxetanes

It is shown that trans-2,3-dialkyloxetanes are formed from the erythro isomers of 2-alkyl-1,3-butanediols, whereas cis-2,3-dialkyloxetanes are formed from the threo isomers.See [1] for communication XXXIX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 164–168, February, 1976.     

Diastereoselectivity of the mercuration of acyclic allylic alcohols

The diastereoselectivity of the mercuration of acyclic alkenes $\text{4}$ can be reversed by changing the substituent in the allylic position; with alcohols the erythro isomers $\text{5}$ and with esters or hemiacetals the threo isomers $\text{6}$ and $\text{8}$ are formed predominantly (Table I).     

Application des relation de Mislow et Raban a la determination de configuration (mesothreo) par resonance magnetique nucleaire

The meso or threo configuration of diastereoisomeric molecules is elucidated on the basis of respective NMR spectra of either isomers. The symmetry relationship (according to Raban and Mislow) between protons or groups are not identical in each isomer, and the consequent differences in chemical shifts and spin-coupling constants permit assignment of configurations.     

Determination of the threo- and erythro- configurations of vicinal diastereomeric derivatives of higher fatty acids with the aid of PMR spectra

Conclusions The PMR spectra of vicinal diastereomeric dihydroxy-, acetoxyhydroxy-, and halohydroxyoctadecanoic and -docosanoic acids and their trimethylsilyl derivatives have been considered. It has been shown that the signals of the methine protons of the erythro isomers appear at lower fields than those of the threo isomers. On passing from the dihydroxy, acetoxyhydroxy, and halohydroxy acids to their TMS derivatives, the signal of the methine proton shifts down-field, and = CHOSi (CH₃)₃ — CHOH is greater for the threo form than for the erythro form, The difference in the chemical shifts of the vicinal methine protons of the dihydroxy, acetoxyhydroxy, and halohydroxy acids and their TMS derivatives can be used to determine the threo and erythro configurations of the corresponding diastereometric derivatives of higher fatty acids.A. A. Zhdanov Leningrad State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 299–305, May–June, 1978.     

STEREOSELECTIVITY OF THE WITTIG-HORNER REACTION WITH BENZYLPHOSPHONATE CARBANIONS AND ALDEHYDES

Abstract

The interaction of Li-diethylbenzylphosphonate 1-Li with aldehydes 2 is studied at different reaction conditions, the corresponding β-hydroxyethanephosphonate 3 being isolated. It is found that in these cases the aldol stage of the HWE reaction is not stereoselective or threo isomers predominate. The elimination stage leads only to trans-alkene due to the electron and steric influence of the substituents at the phosphorus atom.