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Due to the chemoselective dehalogenation by SmI2, the addition of a-halomethylsulfones to carbonyl compounds afforded ,β-hydroxysulfones. Those reactions with α-bromomethylsulfones gave the products in moderate to good yields. The SmI2-mediated addition of gem-dihalomethylsulfones to ketones also afforded α-halo-β-hydroxysulfones in moderate yields. 相似文献
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Lophenol, cholest-4α-methyl-7-en-3β-ol (1), obtained from Dracaena cochinchinensis (Lour.) S. C. Chen, was structurally modified. It was acetylated to protect 3β-hydroxyl group, and then oxidised by selenium dioxide in acetic acid to give cholest-4a-methyl-8-en-3β, Ta-diol diacetate (3). This compound 3 is unstable in chloroform solution or when heated and easily converted to a diene compound, cholest-4a-methyl-7,14-dien-3β-ol acetate (4). The structures of 3 and 4 were elucidated by means of IR, ^1H NMR, ^13C NMR and MS, and the absolute configuration of 3 was established by X-ray crystallography. The property of 3 was also discussed in this paper. Both 3 and 4 are new compounds and were reported for the first time. 相似文献
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Selective α-Bromination of β-Keto Esters in Reusable PEG-400 under Mild and Catalyst-free Conditions
An efficient bromination protocol for the synthesis of α-bromo-β-keto esters has been developed. In PEG-400 (poly(ethylene glycol-400)), a variety of β-keto esters were treated with NBS (N-bromosuccinimide) at room temperature to selectively afford the corresponding α-monobromination products in excellent yields. It is noteworthy that the reaction was conducted under mild, environmentally benign and catalyst-free conditions. 相似文献
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A series of homoallyl β′,γ′-unsaturated amines were synthe sized via 1,2-addition of α,β-unsaturated imines with allylsamarium bromide in excellent yields under mild and neutral conditions. 相似文献
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The cross-coupling reaction of trans-alkenylboronic acids with a-bromoacetic esters was firstly studied. It was found that using Pd(OAc)2 as catalyst, a bulky electron-rich phospine, (2-dicyclohexylphospino-biphenyl) as ligand, the reaction can be readily accomplished to give specific (E)-b,g-unsaturated esters in high yields. 相似文献
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IntroductionBiotransformationsofnitriles ,eitherthroughanitri lase catalyzeddirectconversiontothecarboxylicacidsorviaanitrilehydratase catalyzedhydrationtotheamidesfollowedbythehydrolysistotheacidsmediatedbyanamidase ,haveprovidedausefulandenvironmental… 相似文献
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本文报道一种安全,环境有好,经济实用的合成b氨基酸衍生物的新方法。利用α,β不饱和化合物和脂肪族胺,通过无溶剂、无催化的aza-Michael加成反应,高产率的合成b氨基酸衍生物。 相似文献
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α-Bromo chalcones containing 2-thiene ring were prepared in good yields by the condensation of 1-(thien-3-yl)ethanone with aromatic aldehydes, followed by bromination with bromine and selective dehydrobromination with triethyl amine at room temperature. 相似文献
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Electron impact-induced fragmentation mechanism of Trans-α-Aryl-β-enamino esters were investigated using mass-analyzed ion kinetic energy (MIKE) spectrometry and high resolution accurate mass data It was found that the main characteristic fragmentations of compounds studied were:an odd electron ion M^ -EtOH was formed by losing a neutral molecule of ethanol;and the skeletal rearrangements took place;and the ring opening reaction happened after losing a carbon monoxide;and the typical McLafferty rearrangement underwent in ester group.The cycliztion reation caused by losing neutral molecule of TsNH2 due to the ortho-effects of substituted group of gromatic ring was also observed. 相似文献
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An efficient method for the selective hydrogenation of a series of α,β-epoxyketones to β-hydroxyketones using catalytic amount of two sulfinyl analogues of NAD^+ model compounds is reported. The lack of any diastereoselectivity for the formation of β-hydroxyketones with optically pure sulfinyl analogue of NAD^+ model supports the radical mechanism proposed previously. 相似文献
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手性噁唑硼烷催化α-和β-氨基酮不对称还原反应立体选择性的AM1过渡态模型研究 总被引:1,自引:0,他引:1
AM1 transition state (TS) models were developed for the enanfioselecfivifies in the reductions of α-and β-aminoketones catalyzed by (S)-4-benzyl-5,5-diphenyl-1,3,2-oxazaborolidine. The result showed that β-aminoketone gave better enanfioselectivity than its α-analog. Different chiralifies of the final products were obtained, R for the former and S for the latter. These semiempirical TS models are consistent with the experimental data. 相似文献
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Introduction Asakindofversatileintermediates ,α oxoketenedithioacetals 1(Fig .1)areimportantinorganicsynthe sis1andmostworksarefocusedontheα oxoketenedimethylthioacetals .2 Inourstudies ,itisfoundthatsomereactionsuponthesekindofintermediatesaremodulatedbythe… 相似文献
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用氢谱、红外光谱、X-射线粉末衍射、热分析、元素分析等测试方法研究了Veronicafolin (3,5,4′-三羟基-6,7,3′-三甲氧基黄酮) 和β-环糊精 (β-CD) 的固体包合物的谱学特征。元素分析结果显示形成Veronicafolin-β-CD·20H2O包合物,其中C:39.58%, H: 5.75%,表明包合物中主客体比为1∶1。该包合类型属于AL-型。通过紫外-可见分光光度法研究了在羟丙基-β-环糊精(HP-β-CD)的存在下Veronicafolin的相溶解度曲线,测得校正曲线为y = 24148x + 0.0075 (r=0.9999),相溶解曲线为y=0.4738x-2.0×10-7 (r=0.9490),包结平衡常数Ks为4.5×106mol-1。HP-β-CD提高了黄酮醇Veronicafolin的溶解度。 相似文献
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本文考察了溶剂、温度、反应时间和7-芳基等对3-次苄基6-氟-硫色满酮与3-氨基-1,2,4-三氮唑的环缩合反应的影响。实验结果表明在环缩合反应中同时生成了并四环的二氢嘧啶和嘧啶。而且高温时,并四环二氢嘧啶可以在没有脱氢剂的条件下直接脱氢生成嘧啶。文中合成的化合物结构经氢核磁共振谱、质谱、元素分析和X-射线单晶衍射确证。并对同时生成并四环二氢嘧啶和嘧啶的环缩合反应的机理进行了探讨。 相似文献
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In order to search for novel agrochemicals with high activity and low toxicity, a series of phosphonate derivatives containing 1,2,3-triazole and thiazole rings were designed and synthesized using 2-chloro-5-(chloromethyl)- thiazole as the starting material. Their structures were confirmed by IR, ^1H NMR, ^31p NMR, EI-MS or ESI-MS and elemental analyses. The crystal structure of 7a was determined by single crystal X-ray diffraction. Preliminary bioassays indicated that most of the target compounds did not display insecticidal activities, but a fraction of them possessed herbicidal and fungicidal activities to some extent. 相似文献
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A series of KF/Al2O3 catalyzed Michael-addition reactions between malononitrile and α,β-unsaturated cycloketones in DMF solution were studied. At room temperature, 2-cyano-3-aryl-3-(1,2,3,4-tetrahydronaphthalen-1-one-2-yl) propionitrile derivatives were synthesized by the reaction between 2-arylmethylidene-1,2,3,4-tetra-hydronaphthalen-1-one and malononitrile. However, if the temperature was increased to 80℃, 2-amino-3-cyano-4-aryl-4H-benzo[h]chromene derivatives were obtained in high yields. When the α,β-unsaturated ketones were replaced by 2,6-biarylmethylidenecyclohexanone or 2,5-biarylmethylidenecyclopentanone, another series of 2-amino-3-cyano-4H-pyran derivatives was isolated successfully. The structures of the products were confirmed by X-ray diffraction analysis. 相似文献