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1.
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. 相似文献
2.
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 总被引:4,自引:0,他引:4
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. 相似文献
3.
Dr. Naohiko Yoshikai Sobi Asako Takeshi Yamakawa Dr. Laurean Ilies Prof. Dr. Eiichi Nakamura 《化学:亚洲杂志》2011,6(11):3059-3065
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. 相似文献
4.
Dr. Hayato Ishikawa Takaki Suzuki Dr. Hideo Orita Dr. Tadafumi Uchimaru Prof. Dr. Yujiro Hayashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(42):12616-12626
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. 相似文献
5.
Nagatoshi Nishiwaki Shotaro Hirao Jun Sawayama Haruyasu AsaharaRyuichi Sugimoto Kazuya KobiroKazuhiko Saigo 《Tetrahedron》2014
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. 相似文献
6.
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. 相似文献
7.
Fernández M Vicario JL Reyes E Carrillo L Badía D 《Chemical communications (Cambridge, England)》2012,48(15):2092-2094
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. 相似文献
8.
[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. 相似文献
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10.
Angela Kinnell Thomas Harman Matilda Bingham Alan Berry Adam Nelson 《Tetrahedron》2012,68(37):7719-7722
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. 相似文献
11.
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。 相似文献
12.
Dr. Anna Żądło‐Dobrowolska Dr. Szymon Kłossowski Dr. Dominik Koszelewski Daniel Paprocki Prof. Ryszard Ostaszewski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(46):16684-16689
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. 相似文献
13.
Kang T Kim WY Yoon Y Kim BG Lee HY 《Journal of the American Chemical Society》2011,133(45):18050-18053
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. 相似文献
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15.
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. 相似文献
16.
[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. 相似文献
17.
S. Sicsic 《Tetrahedron》1974,30(2):277-281
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. 相似文献
18.
Güell M Martín N Altable M Filippone S Martín-Domenech A Solà M 《The journal of physical chemistry. A》2007,111(24):5253-5258
Substitution of a H atom by an alkyl group on the terminal carbon of the alkyne moiety of 1,6-fullerenynes has a strong impact on the products of the reaction undergone by this species after thermal treatment. While the reaction of 1,6-fullerenynes bearing an unsubstituted alkyne moiety results in the cycloaddition of the alkyne group to the fullerene double bond leading to cyclobutene-fused derivatives, the presence of an alkyl substituent leads to the formation of allenes. In the present work, we have performed an exhaustive theoretical analysis of all possible reaction mechanisms leading to cyclobutene-fused derivatives and allenes to offer an explanation of the reactivity differences observed. The results obtained show that formation of cyclobutene-fused derivatives occurs through a stepwise diradical reaction mechanism, while allene formation proceeds through a concerted way involving an uncommon intramolecular ene process. For the 1,6-fullerenynes bearing a substituted alkyne, the ene reaction path leading to allenes has an energy barrier somewhat lower than the stepwise diradical mechanism for the cyclobutene-fused derivative formation, thus explaining the outcome of the reaction. 相似文献
19.
A supramolecular allosteric catalyst that exhibits a PCR-like cascade reaction is reported. The complex is triggered by a reaction with an acetate ion, which turns on a catalytic cascade that exponentially increases acetate ion concentration through an acyl transfer reaction. 相似文献
20.
Prof. Dr. J. Stephen Clark Dr. Chao Xu 《Angewandte Chemie (International ed. in English)》2016,55(13):4332-4335
A highly efficient 12‐step synthesis of the marine alkaloid (?)‐nakadomarin A has been accomplished. The key advanced intermediate, a tetracyclic ketone derivative, was constructed in just seven steps using a sequence that includes an asymmetric Pauson–Khand reaction, an Overman rearrangement reaction, a ring‐closing metathesis reaction, and an amination reaction. Late introduction of the furan ring during the synthesis of (?)‐nakadomarin A means that the key tetracyclic ketone derivative has the potential to serve as an advanced intermediate for the synthesis of related marine alkaloids. 相似文献