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1.
A diastereoselective method for the synthesis of chiral pyrrolidine and piperidine ring containing compounds was described. The protocol of bromination followed by aminocyclization furnishes an easily handled while highly efficient procedure for the intramolecular amidation of an isolated double bond. High diastereomeric excess was observed in this synthetic procedure. 相似文献
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Zhen Liu Jiahao Chen Hou‐Xiang Lu Xiaohan Li Yang Gao John R. Coombs Matthew J. Goldfogel Keary M. Engle 《Angewandte Chemie (International ed. in English)》2019,58(47):17068-17073
We report the development of palladium(0)‐catalyzed syn‐selective 1,2‐carboboration and ‐silylation reactions of alkenes containing cleavable directing groups. With B2pin2 or PhMe2Si‐Bpin as nucleophiles and aryl/alkenyl triflates as electrophiles, a broad range of mono‐, di‐, tri‐ and tetrasubstituted alkenes are compatible in these transformations. We further describe a directed dearomative 1,2‐carboboration of electron‐rich heteroarenes by employing this approach. Through use of a removable chiral directing group, we demonstrate the viability of achieving stereoinduction in Heck‐type alkene 1,2‐difunctionalization. This work introduces new avenues to access highly functionalized boronates and silanes with precise regio‐ and stereocontrol. 相似文献
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One‐Pot Tandem Diastereoselective and Enantioselective Synthesis of Functionalized Oxindole‐Fused Spiropyrazolidine Frameworks 下载免费PDF全文
Liang‐Yong Mei Dr. Xiang‐Ying Tang Prof. Dr. Min Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13136-13142
A highly efficient palladium(0)‐catalyzed asymmetric [3+2] cycloaddition using 3‐diazooxindoles serving as dipolarophiles affords functionalized pyrazolidine derivatives in an atom‐economical way. In addition, by trapping the pyrazolidine derivatives with maleimides, the corresponding spiropyrazolidine oxindoles containing multiple stereogenic centers have been obtained in high yields along with moderate to good levels of diastereoselectivity and enantioselectivity under mild conditions. Thus, a novel three‐component one‐pot tandem reaction has been developed. 相似文献
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This article describes a simple method for the synthesis of roxifiban, a potent glycoprotein GP IIb‐IIIa receptor antagonist, by a diastereoselective coupling approach to give >99.9% optical purity. We have also described an attempt to resolve the key synthetic intermediate by diastereomeric ester formation. Although we have been able to separate two diastereomeric esters, the removal of the chiral auxiliary led to partial racemization. 相似文献
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Base‐Controlled Selectivity in the Synthesis of Linear and Angular Fused Quinazolinones by a Palladium‐Catalyzed Carbonylation/Nucleophilic Aromatic Substitution Sequence 下载免费PDF全文
Jianbin Chen Dr. Kishore Natte Dr. Anke Spannenberg Dr. Helfried Neumann Prof. Dr. Peter Langer Prof. Dr. Matthias Beller Prof. Dr. Xiao‐Feng Wu 《Angewandte Chemie (International ed. in English)》2014,53(29):7579-7583
A new approach for the facile synthesis of fused quinazolinone scaffolds through a palladium‐catalyzed carbonylative coupling followed by an intramolecular nucleophilic aromatic substitution is described. The base serves as the key modulator: Whereas DBU gives rise to the linear isomers, Et3N promotes the preferential formation of angular products. Interestingly, a light‐induced 4+4 reaction of the product was also observed. 相似文献
7.
A simple and efficient four‐step sequence for the synthesis of fused polyether arrays has been developed. Cyclic ethers are installed by sequential alkynyl ether formation, carbocupration, ring‐closing metathesis and hydroboration with acidic workup. Crucially, the alkene required for the subsequent ring formation by ring‐closing metathesis is present in the substrate but is masked in the form of a vinylic silane, which prevents competitive metathesis of the side chain. Generation of the reactive alkene from the unreactive vinylic silane is accomplished by hydroboration and subsequent acid‐mediated Peterson elimination of the intermediate hydroxysilane. 相似文献
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Li Zhou Wen-Guang Yan Prof. Dr. Xiu-Li Sun Prof. Dr. Lijia Wang Prof. Dr. Yong Tang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(43):19126-19131
A highly enantioselective synthesis of various chiral heterobicyclic molecules including spiroaminals and fused bicyclic acetals has been developed via a chiral copper catalyzed cyclopropanation-rearrangement (CP-RA) approach under mild reaction conditions. Remarkably, the asymmetric CP-RA for exocyclic vinyl substrates without a pro-stereogenic carbon at the β-position has been realized for the first time and a broad substrate scope with excellent results (33 examples; 34–99 % yields; >95/5 dr and 91–99 % ee) has been achieved. An application of a successive enantioselective CP-RA approach was also described, providing a concise access to complex chiral heteropolycycles. 相似文献
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以甘露醇和山梨醇为原料,合成了2个新的手性膦配体,并用这些新的手性膦配体与钯原位生成的催化剂体系催化苯乙烯的不对称氢酯基化反应,得到R构型的2-苯基丙酸甲酯,其ee值分别为28.5%和13.6%。 相似文献
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Zachary J. Garlets Kaia R. Parenti Prof. Dr. John P. Wolfe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5919-5922
The synthesis of cyclic sulfamides by enantioselective Pd‐catalyzed alkene carboamination reactions between N‐allylsulfamides and aryl or alkenyl bromides is described. High levels of asymmetric induction (up to 95:5 e.r.) are achieved using a catalyst composed of [Pd2(dba)3] and (S)‐Siphos‐PE. Deuterium‐labelling studies indicate the reactions proceed through syn‐aminopalladation of the alkene and suggest that the control of syn‐ versus anti‐aminopalladation pathways is important for asymmetric induction. 相似文献
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Development of Enantioselective Palladium‐Catalyzed Alkene Carboalkoxylation Reactions for the Synthesis of Tetrahydrofurans 下载免费PDF全文
Brett A. Hopkins Zachary J. Garlets Prof. Dr. John P. Wolfe 《Angewandte Chemie (International ed. in English)》2015,54(45):13390-13392
The Pd‐catalyzed coupling of γ‐hydroxyalkenes with aryl bromides affords enantiomerically enriched 2‐(arylmethyl)tetrahydrofuran derivatives in good yield and up to 96:4 e.r. This transformation was achieved through the development of a new TADDOL/2‐arylcyclohexanol‐derived chiral phosphite ligand. The transformations are effective with an array of different aryl bromides, and can be used for the preparation of products bearing quaternary stereocenters. 相似文献
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Jeffrey S. Quesnel Laure V. Kayser Alexander Fabrikant Prof. Bruce A. Arndtsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9550-9555
We report a palladium‐catalyzed method to synthesize acid chlorides by the chlorocarbonylation of aryl bromides. Mechanistic studies suggest the combination of sterically encumbered PtBu3 and CO coordination to palladium can rapidly equilibrate the oxidative addition/reductive elimination of carbon–halogen bonds. This provides a useful method to assemble highly reactive acid chlorides from stable and available reagents, and can be coupled with subsequent nucleophilic reactions to generate new classes of carbonylated products. 相似文献
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通过对含烯烃汽油进行溴加成反应,对汽油中烯烃的保留值进行了研究。对171个溴化产物溴代烃进行了定性,并给出了溴代烃所对应的171个烯烃的定性结果,其中对C7前的溴代烃及烯烃组分给出了结构式。定性手段主要依据汽油中混合纯烯烃样品溴化后的气相色谱 质谱联用(GC MS)数据和气相色谱 原子发射光谱(GC AED)的元素比数据,确定溴代烃及其对应烯烃单体的分子式,然后利用已有的烯烃单体文献保留值数据、纯烯烃化合物的反应结果并结合碳数规律和沸点规律,确定了烯烃单体化合物的结构。该方法最大的优点是实现了选择性检测烯烃,从而排除了其他烃类化合物对烯烃测试的干扰,因此对于汽油中烯烃的分布有着更直观的反映。 相似文献
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ZuminQiu YunbingHe DianmoZheng FufangLiu 《天然气化学杂志》2005,14(1):40-46
The influences of some factors on the yield of phenylacetic acid in the carbonylation of benzyl chloride were studied in this paper. These factors included the variety and content of catalyst, and that of solvent, way of material feeding, reaction temperature, sodium hydrate concentration, triphenylphosphine content, presence of surfactant, the ratio of organic phase volume to aqueous phase volume etc. The optimum reaction conditions were found to be: with a one-time pour of 0.15g Pd(PPh3)2Cl2, 0.24g PPh3, 75ml NaOH of 3.5mol/L, 20ml benzyl chloride and 55ml n-butyl alcohol, and the reaction was carried out at 50℃ for about 3 hours. The as-obtained yield of phenylacetic acid was as high as 97.6%. In addition, the influences of the presence of phenylacetic acid and air in the reaction system were also studied. The results showed that the presence of air in the system and the entrainment of phenylacetic acid in the circulating organic phase had great influence on the reaction rate, the stability and performance of catalyst and the yield of phenylacetic acid. 相似文献
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Jevgenijs Tjutrins Dr. Rajiv Dhawan Dr. Yingdong Lu Prof. Dr. Bruce A. Arndtsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(44):15945-15954
The palladium‐catalyzed carbonylative coupling of imines, acid chlorides, and dipolarophiles can provide efficient routes to prepare nitrogen‐containing heterocycles. One challenge in developing this reaction, and in the creation of more active catalyst systems, is the lack of data on how this complex transformation proceeds. To address this, we report here the results of our mechanistic studies on this system, and in particular the formation of mesoionic münchnones. This includes the synthesis of key catalytic intermediates, model reactions, and kinetic studies that support the role of these compounds in catalysis. Together, these studies provide a clear picture of the impact of catalyst structure, ligands, and palladium nanoparticles on facilitating the carbonylation of in situ generated iminium salts, and suggest an avenue for the creation of more active catalyst systems. 相似文献
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Yan Zheng Mengke Dong Erdong Qu Jin Bai Prof. Dr. Xiao-Feng Wu Prof. Dr. Wanfang Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(65):16219-16224
A facile synthesis of 4H-benzo[d][1,3]oxazin-4-one derivatives by Pd-catalyzed carbonylative cross-coupling between N-(ortho-bromoaryl)amides and benzene-1,3,5-triyl triformate (TFBen) was developed. This procedure does not require the toxic and flammable gas CO as the carbonyl source and tolerates a wide scope of functional groups. Remarkably, 4H-benzo[d][1,3]oxazin-4-ones incorporated to natural products and drugs can be constructed by this method. 相似文献
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Pd–Carbene Migratory Insertion: Application to the Synthesis of Trifluoromethylated Alkenes and Dienes 下载免费PDF全文
Xi Wang Yan Xu Yifan Deng Yujing Zhou Jiajie Feng Guojing Ji Prof. Dr. Yan Zhang Prof. Dr. Jianbo Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(4):961-965
Pd‐catalyzed cross‐coupling of halides with CF3‐substituted diazo compounds or N‐tosylhydrazones has been explored for the synthesis of CF3‐substituted alkenes and 1,3‐butadienes. Pd–carbene migratory insertion plays the key role in these transformations. 相似文献