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1.
A. Bagaria S. Ramakumar M. Gupta V. S. Chauhan 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(3):o174-o176
The title compound (systematic name: 3‐benzylidene‐6‐isobutylpiperazine‐2,5‐dione), C15H18N2O2, an α,β‐dehydrophenylalanine containing diketopiperazine, crystallizes in the space group P1 with two molecules in the asymmetric unit arranged antiparallel to one another. The α,β‐dehydrophenylalanine (ΔPhe) residue in this cyclic peptide retains its planarity but deviates from the standard conformations observed in its linear analogues. Each type of molecule forms a linear chain with molecules of the same type via pairwise N—H⋯O hydrogen bonds, while weaker C—H⋯O interactions link the chains together to form a three‐dimensional network. 相似文献
2.
PPh3⋅HBr‐DMSO Mediated Expedient Synthesis of γ‐Substituted β,γ‐Unsaturated α‐Ketomethylthioesters and α‐Bromo Enals: Application to the Synthesis of 2‐Methylsulfanyl‐3(2 H)‐furanones
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Kanchan Mal Abhinandan Sharma Dr. Prakas R. Maulik Dr. Indrajit Das 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):662-667
An efficient chemoselective general procedure for the synthesis of γ‐substituted β,γ‐unsaturated α‐ketomethylthioesters from α,β‐unsaturated ketones has been achieved through an unprecedented PPh3?HBr‐DMSO mediated oxidative bromination and Kornblum oxidation sequence. The newly developed reagent system serves admirably for the synthesis of α‐bromoenals from enals. Furthermore, AuCl3‐catalyzed efficient access to 3(2H)‐furanones from the above intermediates under extremely mild conditions are described. 相似文献
3.
(E)‐α,β‐Unsaturated pyrazoleamides undergo facile dienolization to furnish copper(I)‐(1Z,3Z)‐dienolates as the major in the presence of a copper(I)‐(R)‐DTBM‐SEGPHOS catalyst and Et3N, which react with aldimines to afford syn‐vinylogous products as the major diastereoisomers in high regio‐ and enantioselectivities. In some cases, the diastereoselectivity is low, possibly due to the low ratio of copper(I)‐(1Z,3Z)‐dienolates to copper(I)‐(1Z,3E)‐dienolates. (Z)‐Allylcopper(I) species is proposed as effective intermediates, which may form an equilibrium with copper(I)‐(1Z,3Z)‐dienolates. Interestingly, the present methodology is a nice complement to our previous report, in which (E)‐β,γ‐unsaturated pyrazoleamides were employed as the prenucleophiles in the copper(I)‐catalyzed asymmetric vinylogous Mannich‐Type reaction and anti‐vinylogous products were obtained. In the previous reaction, copper(I)‐ (1Z,3E)‐dienolates were generated through α‐deprotonation, which might form an equilibrium with (E)‐allylcopper(I) species. Therefore, it is realized in the presence of a copper(I) catalyst that (E)‐α,β‐unsaturated pyrazoleamides lead to syn‐products and (E)‐β,γ‐unsaturated pyrazoleamides lead to anti‐products. Finally, by use of (E)‐β,γ‐unsaturated pyrazoleamide, (E)‐α,β‐unsaturated pyrazoleamide, (R)‐DTBM‐SEGPHOS, and (S)‐DTBM‐SEGPHOS, the stereodivergent synthesis of all four stereoisomers is successfully carried out. Then by following a three‐step reaction sequence, all four stereoisomers of N‐Boc‐2‐Ph‐3‐Me‐piperidine are synthesized in good yields, which potentially serve as common structure units in pharmaceutically active compounds. 相似文献
4.
A series of β,γ‐unsaturated ketones were isomerized to their corresponding α,β‐unsaturated ketones by the introduction of DABCO in iPrOH at room temperature. The endo‐cyclic double bond (β,γ‐position) on ketone was rearranged to exo‐cyclic double bond (α,β‐position) under the reaction conditions. 相似文献
5.
Dr. Ikuo Sasaki Jumpei Taguchi Hana Doi Prof. Dr. Hajime Ito Dr. Tatsuo Ishiyama 《化学:亚洲杂志》2016,11(9):1400-1405
A new process has been developed for the iridium(I)‐catalyzed vinylic C?H borylation of α,β‐unsaturated esters with bis(pinacolato)diboron (B2pin2). These reactions proceeded in octane at temperatures in the range of 80–120 °C to afford the corresponding alkenylboronic compounds in high yields with excellent regio‐ and stereoselectivities. The presence of an aryl ester led to significant improvements in the yields of the acyclic alkenylboronates. Crossover experiments involving deuterated substrates as well as a mixture of stereoisomers confirmed that this reaction proceeds via a 1,4‐addition/β‐hydride elimination mechanism. Notably, this reaction was also used to develop a one‐pot borylation/Suzuki–Miyaura cross‐coupling procedure. 相似文献
6.
Iodine‐promoted direct diamination of α,β‐unsaturated ketone to form two C?N bonds has been developed starting from chalcone and secondary amine. This reaction was performed in THF at 50 °C in the presence of I2 and K2CO3. The protocol is metal‐free, operationally simple and carried out under mild conditions, providing an effective new way for directing diamination reactions. 相似文献
7.
Synthesis of β‐Haloketones by β‐Addition Reactions of α,β‐Unsaturated Ketones with BX3 (X = Br,Cl) as Halide Source
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A series of β‐bromoketones and β‐chloroketones were synthesized by the addition reactions of α,β‐unsaturated ketones under BX3 (X = Br, Cl) and ethylene glycol reaction system. The α,β‐unsaturated ester also was successfully converted to its corresponding β‐bromoester under the reaction condition. 相似文献
8.
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
9.
Decarbonylative Radical Coupling of α‐Aminoacyl Tellurides: Single‐Step Preparation of γ‐Amino and α,β‐Diamino Acids and Rapid Synthesis of Gabapentin and Manzacidin A
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Dr. Masanori Nagatomo Hayato Nishiyama Haruka Fujino Prof. Dr. Masayuki Inoue 《Angewandte Chemie (International ed. in English)》2015,54(5):1537-1541
A new radical‐based coupling method has been developed for the single‐step generation of various γ‐amino acids and α,β‐diamino acids from α‐aminoacyl tellurides. Upon activation by Et3B and O2 at ambient temperature, α‐aminoacyl tellurides were readily converted into α‐amino carbon radicals through facile decarbonylation, which then reacted intermolecularly with acrylates or glyoxylic oxime ethers. This mild and powerful method was effectively incorporated into expeditious synthetic routes to the pharmaceutical agent gabapentin and the natural product (?)‐manzacidin A. 相似文献
10.
Andrzej Gzella 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):983-985
The structures of methyl 3β‐acetoxy‐12‐oxo‐18β‐olean‐28‐oate [C33H52O5, (I)] and methyl 3β‐acetoxy‐12,19‐dioxoolean‐9(11),13(18)‐dien‐28‐oate [C33H46O6, (II)] are described. In (I), all rings are in the chair conformation, rings D and E are cis and the other rings trans‐fused. In compound (II), only rings A and E are in the chair conformation, ring B has a distorted chair conformation, ring C a distorted half‐boat and ring D an insignificantly distorted half‐chair conformation. 相似文献
11.
Jie Liu Jin Zhu Dr. Hualiang Jiang Prof. Dr. Wei Wang Prof. Dr. Jian Li Prof. Dr. 《化学:亚洲杂志》2009,4(11):1712-1716
An o‐anisidine‐Pd(OAc)2 catalytic system for the direct co‐catalytic Saegusa oxidation of β‐aryl substituted aldehydes to α,β‐unsaturated aldehydes has been developed. The use of o‐anisidine in place of (S)‐diphenylprolinol made the process more simply and cost‐effective. The process not only features the use of unmodified aldehydes rather than enol silyl ethers, but also gives moderate to good yields (44–72 %). 相似文献
12.
Catalytic Michael/Ring‐Closure Reaction of α,β‐Unsaturated Pyrazoleamides with Amidomalonates: Asymmetric Synthesis of (−)‐Paroxetine
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Yu Zhang Yuting Liao Prof. Dr. Xiaohua Liu Qian Yao Yuhang Zhou Dr. Lili Lin Prof. Dr. Xiaoming Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):15119-15124
A highly enantioselective tandem Michael/ring‐closure reaction of α,β‐unsaturated pyrazoleamides and amidomalonates has been accomplished in the presence of a chiral N,N′‐dioxide–Yb(OTf)3 complex (Tf: trifluoromethanesulfonyl) to give various substituted chiral glutarimides with high yields and diastereo‐ and enantioselectivities. Moreover, this methodology could be used for gram‐scale manipulation and was successfully applied to the synthesis of (?)‐paroxetine. Further nonlinear and HRMS studies revealed that the real catalytically active species was a monomeric L ‐PMe2 –Yb3+ complex. A plausible transition state was proposed to explain the origin of the asymmetric induction. 相似文献
13.
The reaction of Ph3P=NLi with various α,β‐unsaturated esters gives access to new N‐(α,β‐unsaturated acyl) phosphinimines, which can undergo intramolecular aza‐Wittig reactions (at 65–110°C) to afford the corresponding nitriles. The structures of all new compounds were established by elementary analyses, IR, 1H‐, 13C‐, and 31P‐NMR spectroscopy. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 49–54, 1999 相似文献
14.
Yi‐Xun Zhang Shauntina H. Jackson Mohamed S. Rajab Frank R. Fronczek Steven F. Watkins 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(4):o219-o221
3β‐Hydroxy‐7‐drimen‐12,11‐olide hemihydrate, C15H22O3·0.5H2O, (I), has two sesquiterpene molecules and one water molecule in the asymmetric unit. The OH groups of both molecules and both H atoms of the water molecule are involved in near‐linear intermolecular hydrogen bonds, having O⋯O distances in the range 2.632 (3)–2.791 (2) Å. 3β‐Acetoxy‐7‐drimen‐12,11‐olide, C17H24O4, (II), has its ring system in very nearly the same conformation as the two molecules of (I). 相似文献
15.
Intramolecular Diels‐Alder reaction (IMDA) precursors are easily available starting from addition of ester functionalized zinc‐copper reagents to cyclohexadienyl‐ and cycloheptadienylirontricarbonyl cation salts. The resulting cyclic 1,3‐dienes containing an α,β‐unsaturated ester functionality underwent smoothly IMDA reaction to afford bridged tricyclic compounds. Bridged heterotricyclic skeletons were also available via IMDA reaction of cyclic 1,3‐dienes bearing an imine or aldehyde functionality. 相似文献
16.
Masood Parvez Oliver E. Edwards Zdzisaw Paryzek 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(4):o249-o251
The structures of 3β‐acetoxy‐9α,11α‐epoxy‐5α‐lanost‐9(11)‐en‐7‐one and 3β‐acetoxy‐9β,11β‐epoxy‐5α‐lanost‐9(11)‐en‐7‐one, C32H52O4, differ in their respective substituted cyclohexanone rings but adopt similar conformations in the other three rings. In both of the crystal structures, weak intermolecular C—H⋯O interactions are present. 相似文献
17.
Hiroyuki Kakei Riichiro Tsuji Dr. Takashi Ohshima Dr. Hiroyuki Morimoto Shigeki Matsunaga Dr. Masakatsu Shibasaki Prof. Dr. 《化学:亚洲杂志》2007,2(2):257-264
The full details of the asymmetric epoxidation of α,β‐unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium–biphenyldiol catalyst, generated from Y(OiPr)3–biphenyldiol ligand–triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various α,β‐unsaturated esters. With this catalyst, β‐aryl α,β‐unsaturated esters gave high enantioselectivities and good yields (≤99 % ee). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5–2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For β‐alkyl α,β‐unsaturated esters, an yttrium–binol catalyst, generated from Y(OiPr)3–binol ligand–triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (≤97 % ee). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (?)‐ragaglitazar, a potential antidiabetes agent. 相似文献
18.
《Journal of heterocyclic chemistry》2017,54(2):965-978
By employing copper dibromide as a catalyst, Michael addition–condensation of 3‐substituted indoles with α,β‐unsaturated ketimines was realized. The reactions afforded a large variety of 9H‐pyrrolo[1,2‐α ]indoles with good yields (up to 99 %). In addition, a plausible reaction mechanism was proposed. 相似文献
19.
Asymmetric Hydrogenation of α,β‐Unsaturated Nitriles with Base‐Activated Iridium N,P Ligand Complexes
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Marc‐André Müller Prof. Dr. Andreas Pfaltz 《Angewandte Chemie (International ed. in English)》2014,53(33):8668-8671
Although many chiral catalysts are known that allow highly enantioselective hydrogenation of a wide range of olefins, no suitable catalysts for the asymmetric hydrogenation of α,β‐unsaturated nitriles have been reported so far. We have found that Ir N,P ligand complexes, which under normal conditions do not show any reactivity towards α,β‐unsaturated nitriles, become highly active catalysts upon addition of N,N‐diisopropylethylamine. The base‐activated catalysts enable conjugate reduction of α,β‐unsaturated nitriles with H2 at low catalyst loadings, affording the corresponding saturated nitriles with high conversion and excellent enantioselectivity. In contrast, alkenes lacking a conjugated cyano group do not react under these conditions, making it possible to selectively reduce the conjugated C?C bond of an α,β‐unsaturated nitrile, while leaving other types of C?C bonds in the molecule intact. 相似文献
20.
Promoted by Samarium diiodide (SmI2), α,β‐unsaturated amides were formed from nitrogen anions (formed in situ by the reduction of nitro compounds) and α,β‐unsaturated esters. This reaction contrasts with the conjugate addition between amines and α,β‐unsaturated esters promoted by samarium triiodide (SmI3) and provides an alternative attractive way to obtain α,β‐unsaturated amides using SmI2. 相似文献