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1.
Shubham Dutta Rajendra K. Mallick Rangu Prasad Vincent Gandon Akhila K. Sahoo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2311-2316
Ynamides are typically more reactive than simple alkynes and olefins. However, a serendipitous observation revealed a rare case where the reactivity of simple alkynes exceeds that of ynamides. This led to the development of a unique sulfur‐radical‐triggered cyclization of yne‐tethered ynamides, which involves attack of the alkyne by a thiyl radical followed by cyclization with the ynamide. A wide range of novel 4‐thioaryl pyrroles that could tolerate common functional moieties and N‐protecting groups were expediently constructed by this strategy. The current method contrasts with the typical cyclization of yne‐ynamides, which involves the attack of the alkyne moiety by the ynamide core. Control experiments and DFT calculations supported the participation of the sulfur radical in the reaction and the regioselective cyclization. The synthetic potential of the substituted pyrroles is also discussed. 相似文献
2.
B. Prabagar Rajendra K. Mallick Rangu Prasad Vincent Gandon Akhila K. Sahoo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2387-2392
A regioselective sulfonyl/sulfinyl migration cycloisomerization cascade of alkyne‐tethered ynamides is developed in the presence of XPhosgold catalyst. This reaction is the first example of a general [1,3]‐sulfonyl migration from the nitrogen center to the β‐carbon atom of ynamides, followed by umpolung 5‐endo‐dig cyclization of the ynamide α‐carbon atom to the gold‐activated alkyne, and final deaurative [1,5]‐sulfinylation. This process allows the synthesis of peripherally decorated unconventional 4‐sulfinylated pyrroles with broad scope from N‐propargyl‐tethered ynamides. In contrast, N‐homopropargyl‐tethered ynamides undergo intramolecular tetradehydro Diels–Alder reaction to provide 2,3‐dihydro‐benzo[f]indole derivatives. Control experiments and density‐functional theory studies were used to study the reaction pathways. 相似文献
3.
The Isolation and Characterization of a Rhodacycle Intermediate Implicated in Metal‐Catalyzed Reactions of Alkylidenecyclopropanes 下载免费PDF全文
Dr. Phillip A. Inglesby Dr. John Bacsa Daniela E. Negru Prof. P. Andrew Evans 《Angewandte Chemie (International ed. in English)》2014,53(15):3952-3956
The isolation and characterization of a rhodacycle intermediate implicated in rhodium‐catalyzed reactions of alkylidenecyclopropanes (ACPs) is described. The structure of the metallacycle was unambiguously determined by X‐ray crystallography and is catalytically competent in the rhodium‐catalyzed carbocyclization and ene‐cycloisomerization reactions of ACPs. This work represents a rare example of the isolation of a metallacycle in a metal‐catalyzed higher‐order carbocyclization reaction and thereby provides important insight into the ligand requirements for the insertion of π‐components. Furthermore, it serves as a convenient synthon for the development of challenging higher‐order carbocyclization reactions, as exemplified by the reaction with an activated allene. 相似文献
4.
Olatz Olaizola Igor Iriarte Giovanna Zanella Enrique Gmez‐Bengoa Iaki Ganboa Mikel Oiarbide Claudio Palomo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14388-14392
A catalyst‐driven one‐pot reaction sequence is developed for the enantio‐ and diastereoselective synthesis of tetrasubstituted cyclohexenes from simple unsaturated ketones or thioesters. The method involves a tertiary amine/squaramide‐catalyzed α‐selective addition of transiently generated trienolates to nitroolefins, subsequent base‐catalyzed double bond isomerization, and an intramolecular (vinylogous) 1,6‐addition reaction, a rare key carbocyclization step that proceeded with essentially perfect stereocontrol. 相似文献
5.
Prof. Jan‐E. Bäckvall 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(37):11498-11523
Palladium‐catalyzed oxidative carbon–carbon bond‐forming annulations, that is, carbocyclization reactions, have recently emerged as efficient and atom‐economical routes to carbo‐ and heterocycles, whereby less functionalized substrates and fewer synthetic steps are needed to obtain a target molecule compared with traditional non‐oxidative carbon–carbon bond‐forming reactions. In this review, the synthetic efforts in palladium‐catalyzed oxidative carbocyclization reactions are summarized. 相似文献
6.
Palladium‐Catalyzed Oxygenative Cross‐Coupling of Ynamides and Benzyl Bromides by Carbene Migratory Insertion 下载免费PDF全文
Yunpeng Gao Dr. Guojiao Wu Qi Zhou Prof. Dr. Jianbo Wang 《Angewandte Chemie (International ed. in English)》2018,57(10):2716-2720
A palladium‐catalyzed oxygenative cross‐coupling of ynamides and benzyl bromides has been developed. After subsequent hydrogenation, α,α‐disubstituted amide derivatives were obtained in good yields. Migratory insertion of α‐oxo palladium carbene species, generated by intermolecular oxidation, is proposed as the key step in this reaction. The study demonstrates the potential of ynamides to serve as carbene precursors in palladium‐catalyzed C?C bond‐forming cross‐coupling reactions. 相似文献
7.
Summaryof main observation and conclusion It could be proposed that gold(I)-catalyzed reactions of ynamides with benzofurazan N-oxidesmightproceed through eitherO-attack or N-attack to affordα-oxo orα-imino Au(I)-carbenoidintermediates.Computational studies were performed to predict that benzofurazan N-oxides are ready to undergo the chemoselective N-attack tothe Au(I)-activatedynamides to generate theα-imino Au(I)-carbenoid intermediate.Experimental studies were carried out to confirm the computational results and the 7-nitroindole derivatives were synthesized in a concise and efficient manner.The unfavored O-attack for benzofurazan N-oxides,which is in contrast to nitrones and pyridine/quinoline N-oxides,in the Au(I)-catalyzed reactions with ynamides is rationalized. 相似文献
8.
Benito Alcaide Prof. Dr. Pedro Almendros Dr. Carmen Pardo Prof. Carolina Rodríguez‐Ranera Dr. Alberto Rodríguez‐Vicente Dr. 《化学:亚洲杂志》2009,4(10):1604-1611
Diastereocontrolled Lewis acid‐catalyzed preparation of enantiopure carbacepham derivatives have been developed starting from 2‐azetidinone‐tethered enals. The BF3?Et2O‐promoted reaction of alkenylaldehydes 1 and 16 is effective as carbocyclization protocol to afford 4‐substituted 5‐hydroxycarbacephams or 3‐substituted 4,5‐dihydroxycarbacephams, respectively, by a type I carbonyl‐ene reaction, while the BF3?Et2O or SnCl4‐mediated type II carbonyl‐ene cyclization of alkenylaldehydes 2 furnishes 3‐methylene 5‐hydroxycarbacephams along with the corresponding 3‐halo 5‐hydroxycarbacepham. The stereochemical outcome of these carbonyl‐ene cyclizations leading to carbacepham derivatives can be explained in terms of six‐membered, cyclic chair‐like transition‐state models. The formation of halocarbacepham derivatives is proposed to proceed by a stepwise mechanism. 相似文献
9.
An efficient zinc‐catalyzed oxidative cyclization of readily available indoly ynamides has been developed, enabling rapid and practical access to a diverse array of valuable medium‐sized lactams in mostly good to excellent yields with wide substrate scope. In addition, such an asymmetric synthesis has also been explored by employing the chiral substrate. 相似文献
10.
Regiocontrolled Gold‐Catalyzed [2+2+2] Cycloadditions of Ynamides with Two Discrete Nitriles to Construct 4‐Aminopyrimidine Cores 下载免费PDF全文
Somnath Narayan Karad Prof. Dr. Rai‐Shung Liu 《Angewandte Chemie (International ed. in English)》2014,53(34):9072-9076
Reported herein is the novel gold‐catalyzed intermolecular [2+2+2] cycloaddition of ynamides with two discrete nitriles to form monomeric 4‐aminopyrimidines, which are pharmaceutically important structural motifs. The utility of this new cycloaddition is demonstrated by the excellent regioselectivity obtained using a variety of ynamides and nitriles. 相似文献
11.
Shubham Dutta Shengwen Yang Rajeshwer Vanjari Rajendra K. Mallick Vincent Gandon Akhila K. Sahoo 《Angewandte Chemie (International ed. in English)》2020,59(27):10785-10790
A three‐component Pd‐catalyzed coupling of ynamides, aryl diazonium salts, and aryl boronic acids for the synthesis of novel triaryl‐substituted enamides is described. This transformation represents the first example of an umpolung regioselective unsymmetrical syn‐1,2‐diarylation/aryl‐olefination of ynamides. The aryl moieties of the diazonium salt (electrophile) and boronic acid (nucleophile) are explicitly incorporated in the electrophilic α‐ and nucleophilic β‐position, respectively, of the ynamide, resulting in a single isomer of the N‐bearing tetrasubstituted olefin. The scope is broad (68 examples), showing excellent functional‐group tolerance. DFT calculations substantiate the rationale of the mechanistic cycle and the regioselectivity. The chemoselectivity and synthetic potential of the enamide products were also studied. 相似文献
12.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(43):13495-13498
Non‐oxidative, regioselective, and convergent access to densely functionalized oxazoles is realized in a functional‐group tolerant manner using alkynyl thioethers. Sulfur‐terminated alkynes provide access to reactivity previously requiring strong donor‐substituted alkynes such as ynamides. Sulfur does not act in an analogous donor fashion in this gold‐catalyzed reaction, thus leading to complementary regioselective outcomes and addressing the limitations of using ynamides. 相似文献
13.
Generation of Oxazolidine‐2,4‐diones Bearing Sulfur‐Substituted Quaternary Carbon Atoms by Oxothiolation/Cyclization of Ynamides 下载免费PDF全文
Hai Huang Junzhen Fan Dr. Guangke He Zhimin Yang Xiaodong Jin Qi Liu Prof. Dr. Hongjun Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(7):2532-2538
A novel method for metal‐free oxothiolation of ynamides to construct oxazolidine‐2,4‐diones bearing sulfur‐substituted quaternary carbon atoms has been developed. It represents a rare C?O bond cleavage of ynamides, as well as a facile and tandem approach for the formation of C?O, C?S, and C?Cl bonds. This redox‐neutral protocol can be applied to the synthesis of multisubstituted oxazolidine‐2,4‐diones with good chemoselectivity and good yields of isolated products under mild conditions. 相似文献
14.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(12):3269-3273
A highly selective palladium‐catalyzed oxidative carbonylation/carbocyclization/alkoxycarbonylation of enallenols to afford spirolactones bearing an all‐carbon quaternary center was developed. This transformation involves the overall formation of three C−C bonds and one C−O bond through a cascade insertion of carbon monoxide (CO), an olefin, and CO. Preliminary experiments on chiral anion‐induced enantioselective carbonylation/carbocyclization of enallenols afforded spirolactones with moderate enantioselectivity. 相似文献
15.
Metal‐Free Cyclization of ortho‐Nitroaryl Ynamides and Ynamines towards Spiropseudoindoxyls 下载免费PDF全文
Niels Marien B. Narendraprasad Reddy Freija De Vleeschouwer Steven Goderis Prof. Kristof Van Hecke Prof. Guido Verniest 《Angewandte Chemie (International ed. in English)》2018,57(20):5660-5664
An efficient metal‐free cascade reaction between 1‐dibromovinyl‐2‐nitro‐substituted arenes and secondary amines results in the formation of polycyclic pseudoindoxyls in a single step. The reaction mechanism leading to these fused ring systems was investigated, and is believed to involve the initial formation of nitroarylated ynamines/ynamides. These intermediates cycloisomerize towards N‐alkenyl‐tethered 2‐aminoisatogens via a carbene intermediate as demonstrated by QTAIM (quantum theory of atoms in molecules) and ELF (electron localization function) analysis. A subsequent intramolecular dipolar cycloaddition afforded the title compounds. 相似文献
16.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(13):3724-3728
A non‐metal approach for accessing α‐oxo carbene surrogates for a C−C bond‐forming bimolecular coupling between ynamides and nucleophilic arenes was developed. This acid‐catalyzed coupling features mild temperature, which is critical for the required temporal chemoselectivity among nucleophiles. The scope of nucleophiles includes indoles, pyrroles, anilines, phenols and silyl enolethers. Furthermore, a direct test of SN2′ mechanism has been provided by employing chiral N,N′‐dioxides which also enlightens the nature of the intermediates in related metal‐catalyzed processes. 相似文献
17.
Zhuo Xin Dr. Søren Kramer Dr. Jacob Overgaard Prof. Dr. Troels Skrydstrup 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):7926-7930
A new synthetic route to the privileged 1,2‐dihydroisoquinolines is reported. This method, which relies on a gold‐catalyzed formal [4+2] cycloaddition between ynamides and imines, provides a new retrosynthetic disconnection of the 1,2‐dihydroisoquinoline core by installing the 1,8a C?C and 2,3 C?N bonds in one step. Both aldimines and ketimines can be used as substrates. In addition, one example of dihydrofuropyridine synthesis is also demonstrated. 相似文献
18.
Reductive Carbocyclization of Homoallylic Alcohols to syn‐Cyclobutanes by a Boron‐Catalyzed Dual Ring‐Closing Pathway 下载免费PDF全文
Dr. Chinmoy Kumar Hazra Jinhoon Jeong Hyunjoong Kim Prof. Dr. Mu‐Hyun Baik Dr. Sehoon Park Prof. Dr. Sukbok Chang 《Angewandte Chemie (International ed. in English)》2018,57(10):2692-2696
The organoborane‐catalyzed reductive carbocyclization of homoallylic alcohols has been developed by using hydrosilanes as reducing reagents to provide a range of 1,2‐disubstituted arylcyclobutanes. The reaction proceeds in a cis‐selective manner with high efficiency under mild conditions. Mechanistic studies, including deuterium scrambling and Hammett studies, and DFT calculations, suggest a dual ring‐closing pathway. 相似文献
19.
Diversity in Gold‐Catalyzed Formal Cycloadditions of Ynamides with Azidoalkenes or 2H‐Azirines: [3+2] versus [4+3] Cycloadditions 下载免费PDF全文
Samir Kundlik Pawar Rajkumar Lalji Sahani Prof. Dr. Rai‐Shung Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10843-10850
Gold‐catalyzed cycloadditions of ynamides with azidoalkenes or 2H‐azirines give [3+2] or [4+3] formal cycloadducts of three classes. Cycloadditions of ynamides with 2H‐azirine species afford pyrrole products with two regioselectivities when the Cβ‐substituted 2H‐azirine is replaced from an alkyl (or hydrogen) with an ester group. For ynamides substituted with an electron‐rich phenyl group, their reactions with azidoalkenes proceed through novel [4+3] cycloadditions to deliver 1H‐benzo[d]azepine products instead. 相似文献
20.
Atom‐Economic Synthesis of Fully Substituted 2‐Aminopyrroles via Gold‐Catalyzed Formal [3+2] Cycloaddition between Ynamides and Isoxazoles 下载免费PDF全文
Xin‐Yu Xiao Ai‐Hua Zhou Chao Shu Fei Pan Dr. Ting Li Prof. Dr. Long‐Wu Ye 《化学:亚洲杂志》2015,10(9):1854-1858
A concise and flexible synthesis of fully substituted 2‐aminopyrroles via gold‐catalyzed formal [3+2] cycloaddition between ynamides and isoxazoles has been developed. Under mild reaction conditions, various 2‐aminopyrrole derivatives were obtained in good to excellent yields, thus providing an efficient and atom‐economic way for the construction of fully substituted 2‐aminopyrroles. 相似文献