Stereocontrolled total synthesis of (-)-ephedradine A (orantine)

The stereocontrolled total synthesis of (-)-ephedradine A has been accomplished. The synthesis features an asymmetric C-H insertion reaction, an intramolecular ester-amide exchange reaction, and a Sharpless asymmetric aminohydroxylation reaction. Construction of the complex macrocyclic ring was performed by Ns-strategy and an intramolecular aza-Wittig reaction.     

固体聚合物电解质在肉桂醇电解氧化中的应用(II)——后续化学反应在电催化反应中的地位及其影响因素

对影响肉桂醇电极氧化的各种因素作了进一步的讨论. 实验结果表明固体聚合物电解质内水的含量、pH 以及浸入离子交换膜中的二价锰离子的浓度均对该电极反应的电位以及后续化学反应的速度有很大的影响, 在较高的温度下反应时, 有利手提高生成肉桂醛的电流效率.     

Iron‐Catalyzed C?H Bond Activation for the ortho‐Arylation of Aryl Pyridines and Imines with Grignard Reagents

Direct arylation of the ortho‐C? H bond of an aryl pyridine or an aryl imine with an aryl Grignard reagent has been achieved by using an iron‐diamine catalyst and a dichloroalkane as an oxidant in a short reaction time (e.g., 5 min) under mild conditions (0 °C). The use of an aromatic co‐solvent, such as chlorobenzene and benzene, and slow addition of the Grignard reagent are essential for the high efficiency of the reaction. The present arylation reaction has distinct merits over the previously developed reaction that used an arylzinc reagent, such as its reaction rate and atom economy. Selective C? H bond activation occurs in the presence of a leaving group, such as a tosyloxy, chloro, and bromo group. Studies on a stoichiometric reaction and kinetic isotope effects shed light on the reaction intermediate and the C? H bond‐activation step.     

Regioselective allylzincation of alkenylboronate

[reaction: see text] Boryl substitution on an olefin activates the olefinic double bond toward addition of an organozinc reagent. Addition of an allylic zinc reagent to an alkenylboronate thus takes place smoothly to afford a variety of gem-zincio/boryl species. Theoretical studies with density functional calculations on the reaction pathway revealed that the reaction proceeds via a zincio-ene reaction rather than a bora-Claisen rearrangement.     

High‐Yielding Synthesis of the Anti‐Influenza Neuraminidase Inhibitor (−)‐Oseltamivir by Two “One‐Pot” Sequences

The efficient asymmetric total synthesis of (?)‐oseltamivir, an antiviral reagent, has been accomplished by using two “one‐pot” reaction sequences, with excellent overall yield (60 %) and only one required purification by column chromatography. The first one‐pot reaction sequence consists of a diphenylprolinol silyl ether mediated asymmetric Michael reaction, a domino Michael reaction/Horner–Wadsworth–Emmons reaction combined with retro‐aldol/Horner–Wadsworth–Emmons reaction and retro Michael reactions, a thiol Michael reaction, and a base‐catalyzed isomerization. Six reactions can be successfully conducted in the second one‐pot reaction sequence; these are deprotection of a tert‐butyl ester and its conversion into an acyl chloride then an acyl azide, Curtius rearrangement, amide formation, reduction of a nitro group into an amine, and a retro Michael reaction of a thiol moiety. A column‐free synthesis of (?)‐oseltamivir has also been established.     

Synthesis of vicinally functionalized 1,4-dihydropyridines and diazabicycles via a pseudo-intramolecular process

An α-nitro-δ-keto nitrile readily forms the corresponding ammonium salt immediately upon treatment with an amine. When the amine liberated under equilibrium, the nucleophilic amine and the electrophilic keto nitrile come close to each other to afford so-called an intimate pair. The spatial proximity realized an efficient reaction to give a 2-amino-3-nitro-1,4-dihydropyridine; the reaction proceeded like an intramolecular reaction although it is actually an intermolecular reaction, namely the pseudo-intramolecular reaction. The bifunctionality of the keto nitrile also enabled the pseudo-intramolecular imination followed by tandem cyclization leading to diazabicyclic frameworks.     

Tandem cycloaddition reactions of allenyl diazo compounds forming triquinanes via trimethylenemethane diyls

A tandem reaction strategy for forming triquinanes from linear allenyl diazo compounds through an intramolecular 1,3-dipolar cycloaddition reaction of an allenyl diazo group that generates a trimethylenemethane (TMM) diyl followed by an intramolecular [2 + 3] TMM diyl cycloaddition reaction has been developed. The new tandem cycloaddition reaction is readily applicable to the synthesis of complex molecules with high versatility and efficiency.     

Recent advances in Gomberg-Backmann biaryl synthesis

The Gomberg-Bachmann reaction is an intermolecular aryl-aryl cross-coupling reaction using an arenediazonium salt and an arene. This digest review surveys recent advances in the Gomberg-Bachmann reaction. More specifically, it focuses on reaction systems that include 1) transition-metal-induced systems, 2) organic promoter-induced systems, 3) electrolytic systems, 4) photoreaction systems, and 5) hybrid systems consisted of a photoredox and a transition-metal catalyst.     

Organocatalytic enantioselective synthesis of 2,3-dihydropyridazines

We have developed an efficient procedure for the easy and straightforward preparation of functionalized dihydropyridazines as highly enantiopure materials by reaction of pyruvaldehyde 2-tosyl hydrazone with a variety of α,β-unsaturated aldehydes using a chiral secondary amine as catalyst. The overall process consists of a cascade reaction involving an initial aza-Michael reaction, in which the stereocentre is installed, followed by an intramolecular aldol reaction/dehydration step.     

Ugi反应在环肽生物碱和小肽衍生物抗生素及细胞毒素类等天然产物合成中的应用

Ugi反应是由1分子醛或酮、1分子胺、1分子异腈和1分子羧酸4个组分通过缩聚反应生成α- 酰氨基酰胺类化合物的反应。 具有反应条件温和、产率高和原子经济性好等特点。 该反应还可与Suzuki、Heck和Smiles等经典反应偶联,使得其在天然产物合成方面得到越来越多的关注。 本文概括总结了近几十年来Ugi反应在一些天然产物合成中的应用。     

Development of an organo- and enzyme-catalysed one-pot,sequential three-component reaction

A one-pot, three-component process is described which involves both organo- and enzyme-catalysed carbon–carbon bond-forming steps. In the first step, an organocatalyst catalyses the aldol reaction between acetaldehyde and a glyoxylamide. After dilution with additional aqueous buffer, and addition of pyruvate and an aldolase enzyme variant, a second aldol reaction occurs to yield a final product. Crucially, it was possible to develop a reaction in which both the organo- and enzyme-catalysed reactions could be performed in the same aqueous buffer system. The reaction described is the first example of a one-pot, three-component reaction in which the two carbon–carbon bond-forming processes are catalysed using the combination of an organocatalyst and an enzyme.     

Diels-Alder reaction of maldoxin with an isopropenylallene

The Diels-Alder reaction of maldoxin with an isopropenylallene at 60-75 °C afforded an adduct closely related to chloropestolide A (24%) and a second adduct (0-11%) that underwent an ene reaction to generate the chloropupukeanolide D (11-22%) skeleton. The Diels-Alder reaction occurred with good selectively (>5:1) from a single face of maldoxin under much milder conditions than previously reported for the analogous dimethoxycyclohexadienone. Furthermore, the ene reaction took place under mild conditions, whereas the analogous Diels-Alder adduct from the dimethoxycyclohexadienone did not undergo an ene reaction.     

Enzymatic Ugi Reaction with Amines and Cyclic Imines

The application of the Ugi reaction to the construction of new peptide scaffolds is an important goal of organic chemistry. To date, there are no examples of the Ugi reaction being performed with a cyclic imine and amine simultaneously. The application of 2‐substituted cyclic imines in an enzymatic three‐component Ugi‐type reaction provides an elegant and attractive synthesis of substituted pyrrolidine and piperidine derivatives in up to 60 % yield. Results on studies of the selection of an enzyme, amount of water, and solvent used in a novel three‐component Ugi reaction and the limitations thereof are reported herein. The presented methodology exploiting enzyme promiscuity in the multicomponent reaction fulfills the requirements associated with green chemistry. Several methods, such as isotope labeling and enzyme inhibition, were used to probe the possible mechanism of this complex synthesis. This research is the first example of an enzyme‐catalyzed Ugi‐type reaction with an imine, amine, and isocyanide.     

手性磺酰胺有机小分子催化剂在不对称催化反应中的应用进展

有机小分子催化的不对称合成反应是目前研究最为活跃的领域之一.综述了磺酰胺类衍生物作为小分子催化剂在不对称反应(Michael加成反应、Mannich反应、羟醛缩合反应等)中的应用,讨论了磺酰胺中NH的酸性以及氢键性质在不对称催化反应中的的作用.     

Domino reactions that combine an azido-Schmidt ring expansion with the Diels-Alder reaction

[reaction: see text] The combination of the intramolecular Schmidt reaction with the Diels-Alder reaction provides expedient access to a variety of heterocycles. Two different modes of reaction planning are presented. In one, the azide and ketone moieties necessary for the intramolecular Schmidt reaction originate on different molecules that are reacted and subsequently undergo a ring-adjustment step. Alternatively, an azido ketone can be used provided the ketone is deactivated by its presence in an enone.     

Trost氮杂半冠醚手性配体在不对称催化反应中的应用

双功能手性金属络合物催化的不对称反应是目前有机化学研究的热点之一。本文综述了氮杂半冠醚手性配体与金属有机试剂络合的双金属催化剂,在催化不对称aldol反应、不对称Henry反应、不对称Michael反应、不对称Mannich反应、不对称Friedel-Crafts烷基化反应、不对称炔基化反应、不对称硅氰化反应、共聚反应、去对称化反应以及不对称Nozaki-Hiyama烯丙基化反应体系中的应用进展,重点介绍了不同催化体系对催化剂和反应底物之间立体效应和电子效应的影响,总结了控制反应立体选择性的规律以及有关催化反应的机理。     

Intramolecular Diels-Alder Reaction of Furans with Allenyl Ethers Followed by Phenylthio and Trialkylsilyl Groups Rearrangement

A new reaction involving an intramolecular Diels-Alder reaction of a furan diene with an allenyl ether dienophile followed by phenylthio group rearrangement was discovered. Treatment of the propargyl ethers 2a-c with t-BuOK in t-BuOH at 85 ° C gave the phenylthio group rearrangement products 5a-c and 6a-c . A reaction involving an intramolecular Diels-Alder reaction of a furan diene with an allenyl ether dienophile followed by trialkylsilyl group rearrangement is also demonstrated.     

Sur un effet de solvant inhabituel sur une reaction de menschutkin intramoleculaire

The influence of solvation on the reaction rate of an intramolecular quaternisation, may be different from the rate observed for an intermolecular reaction of the same type. In the intermolecular reaction, if the polarity of an aprotic solvent increases, the partially charged transition state is more stable than the initial state. In the contrary, for an intramolecular reaction the conformation of the different states (initial and transition) plays an important role. So that, if the polarity of an aprotic solvent increases, one conformation of the uncharged initial state may be, by its geometry more stable than the partially charged transition state. An interpretation based on the conformation, explains why in one case and in comparison with CH₃CN, methanol accelerates the intramolecular reaction whereas the contrary is always observed for an intermolecular one.     

Coupling of Propane with CO2 to Propylene Catalyzed by V–Fe Modified KIT-6 Zeolites

Catalysis Surveys from Asia - Propane dehydrogenation to propene is an endothermic reaction and CO2 hydrogenation to light olefins is an exothermic reaction. Using the CO2 hydrogenation reaction to...     

二氯乙烯锗烯与甲硫醛环加成的反应机理

利用MP2/6-311+G*方法计算了单线态二氯乙烯锗烯与甲硫醛的各种反应机理. 计算结果表明两者之间的环加成反应具有很好的选择性, 优势反应路径分为三步: 首先两种反应物经过无能垒的放热反应形成中间体INT, 然后INT经历过渡态TS3异构化为P31, 最后P31继续与甲硫醛反应形成二环杂环化合物P33. 其中第一步反应放热103.4 kJ·mol-1, 后两步反应能垒分别为0.7 和32.3 kJ·mol-1.