Palladium‐Catalyzed Bromoalkynylation of CC Double Bonds: Ring‐Structure‐Dependent Synthesis of 7‐Alkynyl Norbornanes and Cyclobutenyl Halides

Li, Yibiao; Liu, Xiaohang; Jiang, Huanfeng; Liu, Bifu; Chen, Zhengwang; Zhou, Peng

doi:10.1002/anie.201100002

Cited by 108 publications

(46 citation statements)

References 75 publications

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“…The latter are readily accessible and decompose, with the exception of fluoroacetylenes, only at higher temperatures . Until recently, the simultaneous addition of one halogen atom and one alkyne unit (haloalkynylation) to a carbon–carbon double bond was only possible for norbornene systems . We were able to demonstrate for the first time that the chloroalkynylation of 1,1‐disubstituted alkenes 2 can be achieved through gold(I) catalysis leading to the homopropargyl chlorides 3 in good yields (Scheme a) .…”

Section: Methodsmentioning

confidence: 82%

Gold(I)‐Catalyzed Haloalkynylation of Aryl Alkynes: Two Pathways, One Goal

Kreuzahler

Haberhauer

2020

Angew Chem Int Ed

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Haloalkynylation reactions provide an efficient method for the simultaneous introduction of a halogen atom and an acetylenic unit. For the first time, we report a gold(I)‐catalyzed haloalkynylation of aryl alkynes that delivers exclusively the cis addition product. This method enables the simple synthesis of conjugated and halogenated enynes in yields of up to 90 %. Notably, quantum chemical calculations reveal an exceptional interplay between the place of the attack at the chloroacetylene: No matter which C−C bond is formed, the same enyne product is always formed. This is only possible through rearrangement of the corresponding skeleton. Hereby, one reaction pathway proceeds via a chloronium ion with a subsequent aryl shift; in the second case the corresponding vinyl cation is stabilized by a 1,3‐chlorine shift. 13C‐labeling experiments confirmed that the reaction proceeds through both reaction pathways.

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Section: Methodsmentioning

confidence: 82%

Gold(I)‐Catalyzed Haloalkynylation of Aryl Alkynes: Two Pathways, One Goal

Kreuzahler

Haberhauer

2020

Angew Chem Int Ed

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“…[8] On this basis, we decided to explore the behavior of this type of ligand in the Au I -catalyzed cycloaddition of bromoalkynes with alkenes.T he reactiono f( bromoethynyl)benzene 1a with cyclopentene 2 was chosen asaplatform for preliminary studies. Considering the high synthetic value of the haloalkynylation products and the absence of precedents for this reaction, [9,10] further efforts were directed to find conditions to increase the yield of the insertion product 4a.S ubtle differences in the ligand structure and reaction conditions provedt oh ave am arked effect in the product distribution. To check whethert his minor product is also formed under Zhang's experimental conditions, the reaction was also performed with IPrAuCl precatalyst B.Inf act, as imilaramount(15 %) of 4a was obtained in this case, along with the reported [2+ +2] cycloaddition product 3,o btained in 41 %y ield (entry 2).…”

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confidence: 99%

Au^I‐Catalyzed Haloalkynylation of Alkenes

García-Fernández

Llorente

Iglesias‐Sigüenza

et al. 2019

Chemistry A European J

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The formal insertiono fa lkenes into aromatic chloro-a nd bromoalkynes takes place under cationic gold catalysis. This haloalkynylation reactionc an be performed with cyclic, gem-disubstituted and monosubstituted alkenes, using BINAP,t riazolo [4,3-b]isoquinolin-3-ylidenel igands or SPhos, respectively.T he products were isolated in moderatet oe xcellent yieldsa nd with complete diastereo-and regioselectivity;t he halogen atom bondingt he more substituted carbon of the alkene.P reliminary experiments showedt hat the enantioselective haloalkynylation of cyclopentene can be performedw ith (S)-BINAP to afford the insertion productsw ithmoderate to good enantioselectivities.Cationicg old complexes are the most active catalysts for the electrophilic activation of carbon-carbon multiple bonds, being particularlye fficient and selective for alkynes. [1] In 2010, Echavarren and co-workers discoveredt he intermolecular [2+ +2] cycloadditiono fa lkenes and alkynes, one of the most fundamental transformations in this field and av aluablet ool for the synthesiso fc yclobutenes [2] (Scheme 1A). Very recently, the group of Zhang showed that chloroalkynes are also suitable substrates in such [2+ +2] cycloadditions, leading in this case to valuable chlorocyclobutenes [3] (Scheme 1B). The reaction with bromoalkynes,h owever, led to ap oor yield of the cycloadduct in as ingle example.On the other hand, we have been interested in the design of NHCs featuring heterobi(tri)cyclic architectures,w hich offers opportunities for the modulation of their sterica nd electronic properties. [4] Within this group, triazolylidenes embedded in tricyclic architectures exhibit an extraordinary p-acceptor character,q uantitatively assessed by 77 Se NMR spectroscopy [5] in a model ligand L (Figure 1). [6] Combinedw ith ah igh level of steric protection, the electronic properties of this type of NHCs make them particularly attractive for Au I -catalyzed reactions, particularly fort hose in which the activation of the substrate is the rate-limitings tep. [7] Moreover,t he performance of such ligands hasa lready been shown in challenging asymmetric intermolecular cycloaddition reactions of allenamides. [8] On this basis, we decided to explore the behavior of this type of ligand in the Au I -catalyzed cycloaddition of bromoalkynes with alkenes.T he reactiono f( bromoethynyl)benzene 1a with cyclopentene 2 was chosen asaplatform for preliminary studies. The reaction performed with precatalyst A (L·AuCl) under Zhang's conditions {5 mol % B ((IPr·AuCl), IPr = 1,3bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene)/ 10 mol %N aBArF (sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) in DCE, [1a] = 0,1 m,4 0 8C} afforded the expected cyclobutene 3,i solated in 46 %y ield and,s urprisingly,t he bromoalkynylation (formal insertion) product 4a was isolated as a minor component in 16 %y ield (Table 1, entry 1). To check whethert his minor product is also formed under Zhang's experimental conditions, the reaction was also performed with IPrAuCl p...

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“…Due to the sp hybridization of the triple bonds and the attached halogen atom, haloalkynes exhibit rich and tunable reactivities under transition‐metal catalysis and have emerged as a powerful and versatile synthon in the field of synthetic and materials chemisty . Previously, we have reported the 1,7‐haloalkylation of norbornenes with haloalkynes, which involved a key carbopalladation intermediate A (Scheme ) . Inspired by this work, as well as our continuous interest in haloalkyne chemistry– and the transformations of vinyl palladium intermediates, we envision that the carbopalladation intermediate A derived from haloalkyne and norbornene might further undergo a carbopalladation pathway to the alkynyl moiety, and then a vinyl palladium intermediate B would be generated .…”

Section: Methodsmentioning

confidence: 84%

Conversion of Triple Bonds into Single Bonds in a Domino Carbopalladation with Norbornene

Zhu

Chen

Zhu

et al. 2017

Chemistry An Asian Journal

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A domino carbopalladation reaction of haloalkynes is presented. Remarkably, the four-time carbopalladation process converts the carbon-carbon triple bonds of haloalkynes stepwise into carbon-carbon double bonds, and finally to carbon-carbon single bonds. Features of this reaction are that the carbon-carbon double bonds of stable vinyl palladium intermediates are transformed into carbon-carbon single bonds with the generation of unstable alkyl palladium intermediates. The subsequently formed π-allylpalladium species are independently trapped by N-tosylhydrazones, boronic acids, and B pin in a highly diastereoselective manner, delivering the corresponding polycyclic and twisted products with a bicyclo[3.2.1]oct-2-en-3-yl)tricyclo[3.2.1.0 ]octane core skeleton in moderate to good yields via C-C and C-B bond formations. Significantly, the dual roles of norbornenes, ring construction and ring expansion, and the identification of electron-rich tri(2-furyl)phosphine as the ligand are found to be critical for the success of these transformations.

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Palladium‐Catalyzed Bromoalkynylation of CC Double Bonds: Ring‐Structure‐Dependent Synthesis of 7‐Alkynyl Norbornanes and Cyclobutenyl Halides

Cited by 108 publications

References 75 publications

Gold(I)‐Catalyzed Haloalkynylation of Aryl Alkynes: Two Pathways, One Goal

Gold(I)‐Catalyzed Haloalkynylation of Aryl Alkynes: Two Pathways, One Goal

Au^I‐Catalyzed Haloalkynylation of Alkenes

Conversion of Triple Bonds into Single Bonds in a Domino Carbopalladation with Norbornene

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Palladium‐Catalyzed Bromoalkynylation of CC Double Bonds: Ring‐Structure‐Dependent Synthesis of 7‐Alkynyl Norbornanes and Cyclobutenyl Halides

Cited by 108 publications

References 75 publications

Gold(I)‐Catalyzed Haloalkynylation of Aryl Alkynes: Two Pathways, One Goal

Gold(I)‐Catalyzed Haloalkynylation of Aryl Alkynes: Two Pathways, One Goal

AuI‐Catalyzed Haloalkynylation of Alkenes

Conversion of Triple Bonds into Single Bonds in a Domino Carbopalladation with Norbornene

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Au^I‐Catalyzed Haloalkynylation of Alkenes