1657-53-0Relevant academic research and scientific papers
Heck reactions with very low ligandless catalyst loads accelerated by microwaves or simultaneous microwaves/ultrasound irradiation
Palmisano, Giovanni,Bonrath, Werner,Boffa, Luisa,Garella, Davide,Barge, Alessandro,Cravotto, Giancarlo
, p. 2338 - 2344 (2007)
Heck couplings were carried out ligandless in air with very low catalyst loads under microwave or simultaneous microwave/ultrasound irradiation. Using ligand-free palladium(II) acetate [Pd(OAc)2] in the range of 0.01-0.1 mol% or palladium-oncarbon (Pd/C) 10% in the range of 1.0-2.0 mol%, most aryl iodides and bromides gave high yields under conventional heating (120 °C) in 18 h. MicroWave irradiation alone or, better still, combined with high-intensity ultrasound, strongly promotes the reaction, generally decreasing reaction times to 1 h. Electron-poor aryl chlorides such as 4-chloroacetophenone and l-chloro-4-nitrobenzene reacted with styrene to afford high product yields in the presence of 0.25 mol% Pd(OAc)2 or 2.0-3.0 mol% Pd/C. In several cases the addition of a co-catalyst, either rhodium tris(triphenylphosphine) chloride, 0.005 mol%, or a copper(I) salt (iodide or bromide), 2.0-4.0 mol %, proved very advantageous. 4-Bromo- and 4-chloroacetophenone afforded up to 15 % of oxidation products, namely the corresponding 4-halobenzoic acid and 4-styrylbenzoic acid, a drawback that was avoid ed by working under a nitrogen atmosphere.
Regioselectivity observed in manganese(III) acetate mediated addition of acetylacetone to various alkenes: mechanistic and theoretical studies
Ceyhan, Selin,Cetinkaya, Yasin,Akdag, Akin,Balci, Metin
, p. 6815 - 6824 (2016)
Various alkenes substituted at the 1,2-positions by 2-thiophenyl, 3-thiophenyl, and phenyl substituted by electron-withdrawing and electron-donating groups were treated with acetylacetone in the presence of Mn(OAc)3in acetic acid. In cases wher
Palladium Nanoparticle-Catalyzed Stereoretentive Cross-Coupling of Alkenyl Sulfides with Grignard Reagents
Jeanne-Julien, Louis,Astier, Eloi,Lai-Kuen, René,Genta-Jouve, Grégory,Roulland, Emmanuel
, p. 1430 - 1434 (2018)
Reaction conditions allowing a stereoretentive cross-coupling of alkenyl sulfides with Grignard reagents using ligand-free Pd catalysis are discussed here. The presence of an adequately positioned OH function is a key feature that allows a Mg-promoted Lewis acid activation of the mercaptide leaving group. This easy to implement procedure actually relies on an in situ generation of stable Pd nanoparticles by simply mixing Pd2(dba)3, the Grignard reagent, and the vinyl sulfide cross-coupling partner in THF. The efficiency of this procedure has been demonstrated in a natural product total synthesis context.
Imidazol(in)ium carboxylates as N-heterocyclic carbene ligand precursors for Suzuki-Miyaura reactions
Tudose, Adriana,Delaude, Lionel,André, Beno?t,Demonceau, Albert
, p. 8529 - 8533 (2006)
Simple catalysts formed in situ from palladium acetate and a variety of imidazolium and imidazolinium carboxylates and dithiocarboxylates have been screened in the coupling of aryl halides with trans-2-phenylvinylboronic acid. Imidazol(in)ium carboxylates show an excellent activity, which compares to that displayed by the parent imidazol(in)ium chlorides, whereas imidazol(in)ium dithiocarboxylates are poorly efficient. Interestingly, the base employed exerts a profound influence on the trans/cis stereochemistry of the coupling product.
New Pd-NHC-complexes for the Mizoroki-Heck reaction
Taige, Maria A.,Zeller, Alexander,Ahrens, Sebastian,Goutal, Sigrid,Herdtweck, Eberhardt,Strassner, Thomas
, p. 1519 - 1529 (2007)
The synthesis and structural characterization of novel chelating N-aryl substituted palladium(II)-biscarbene-complexes is reported: 1,1′-bis(4-bromophenyl)-3,3′-methylene-diimidazoline-2,2′-diylidene-palladium(II)-dibromide, 1,1′-bis(4-methoxyphenyl)-3,3′-methylene-diimidazoline-2,2′-diylidene-palladium(II)-dibromide and 1,1′-bis(4-n-butoxyphenyl)-3,3′-methylenediimidazoline-2,2′-diylidene-palladium(II)-dibromide have been synthesized in good yields. The catalytic activity of these 1,1′-aryl-3,3′-methylenediimidazoline-2,2′-diylidene-palladium(II)-dihalogenide complexes was tested for the Mizoroki-Heck reaction in comparison to 1,1′-(bis)methyl-3,3′-methylenediimidazoline-2,2′-diylidene-palladium(II)-dihalogenide complexes and to 1,1′-bis(phenyl)-3,3′-methylene-diimidazoline-2,2′-diylidene-palladium(II)-dibromide. The activity of the aryl substituted catalysts is significantly higher compared to the methyl substituted NHC complexes. They also allow the coupling of arylchlorides with olefins.
Electrochemical Proton Reduction over Nickel Foam for Z-Stereoselective Semihydrogenation/deuteration of Functionalized Alkynes
Valiente, Alejandro,Martínez-Pardo, Pablo,Kaur, Gurpreet,Johansson, Magnus J.,Martín-Matute, Belén
, (2021/12/22)
Selective reduction strategies based on abundant-metal catalysts are very important in the production of chemicals. In this paper, a method for the electrochemical semihydrogenation and semideuteration of alkynes to form Z-alkenes was developed, using a simple nickel foam as catalyst and H3O+ or D3O+ as sources of hydrogen or deuterium. Good yields and excellent stereoselectivities (Z/E up to 20 : 1) were obtained under very mild reaction conditions. The reaction proceeded with terminal and nonterminal alkynes, and also with alkynes containing easily reducible functional groups, such as carbonyl groups, as well as aryl chlorides, bromides, and even iodides. The nickel-foam electrocatalyst could be recycled up to 14 times without any change in its catalytic properties.
Phosphine-Functionalized Chitosan Microparticles as Support Materials for Palladium Nanoparticles in Heck Reactions
Biajoli, André F. P.,Fajardo, André R.,Lemos, Thalia S. A.,de Souza, Jaqueline F.
, (2022/01/11)
Herein, we investigated the activation and stabilization of Pd nanoparticles using microparticles of chitosan-functionalized with phosphine moieties. The catalytic activity of the prepared material was assessed in a series of Heck reactions, which demonst
An Amine-Assisted Ionic Monohydride Mechanism Enables Selective Alkyne cis-Semihydrogenation with Ethanol: From Elementary Steps to Catalysis
Huang, Zhidao,Wang, Yulei,Leng, Xuebing,Huang, Zheng
supporting information, p. 4824 - 4836 (2021/04/07)
The selective synthesis of Z-alkenes in alkyne semihydrogenation relies on the reactivity difference of the catalysts toward the starting materials and the products. Here we report Z-selective semihydrogenation of alkynes with ethanol via a coordination-induced ionic monohydride mechanism. The EtOH-coordination-driven Cl- dissociation in a pincer Ir(III) hydridochloride complex (NCP)IrHCl (1) forms a cationic monohydride, [(NCP)IrH(EtOH)]+Cl-, that reacts selectively with alkynes over the corresponding Z-alkenes, thereby overcoming competing thermodynamically dominant alkene Z-E isomerization and overreduction. The challenge for establishing a catalytic cycle, however, lies in the alcoholysis step; the reaction of the alkyne insertion product (NCP)IrCl(vinyl) with EtOH does occur, but very slowly. Surprisingly, the alcoholysis does not proceed via direct protonolysis of the Ir-C(vinyl) bond. Instead, mechanistic data are consistent with an anion-involved alcoholysis pathway involving ionization of (NCP)IrCl(vinyl) via EtOH-for-Cl substitution and reversible protonation of Cl- ion with an Ir(III)-bound EtOH, followed by β-H elimination of the ethoxy ligand and C(vinyl)-H reductive elimination. The use of an amine is key to the monohydride mechanism by promoting the alcoholysis. The 1-amine-EtOH catalytic system exhibits an unprecedented level of substrate scope, generality, and compatibility, as demonstrated by Z-selective reduction of all alkyne classes, including challenging enynes and complex polyfunctionalized molecules. Comparison with a cationic monohydride complex bearing a noncoordinating BArF- ion elucidates the beneficial role of the Cl- ion in controlling the stereoselectivity, and comparison between 1-amine-EtOH and 1-NaOtBu-EtOH underscores the fact that this base variable, albeit in catalytic amounts, leads to different mechanisms and consequently different stereoselectivity.
Ligand-free (: Z)-selective transfer semihydrogenation of alkynes catalyzed by in situ generated oxidizable copper nanoparticles
Grela, Karol,Kusy, Rafa?
supporting information, p. 5494 - 5502 (2021/08/16)
Herein, we present (Z)-selective transfer semihydrogenation of alkynes based on in situ generated CuNPs in the presence of hydrogen donors, such as ammonia-borane and a green protic solvent. This environmentally friendly method is characterized by operational simplicity combined with high stereo- and chemoselectivity and functional group compatibility. Auto-oxidation of CuNPs after the completion of a semihydrogenation reaction results in the formation of a water-soluble ammonia complex, so that the catalyst may be reused several times by simple phase-separation with no need for any special regeneration processes. Formed NH4B(OR)4 can be easily transformed back into ammonia-borane or into boric acid. In addition, a one-pot tandem sequence involving a Suzuki reaction followed by semihydrogenation was presented, which allows minimization of chemical waste production.
Copper(0) nanoparticle catalyzed Z-Selective Transfer Semihydrogenation of Internal Alkynes
Moran, Maria Jesus,Martina, Katia,Bieliunas, Vidmantas,Baricco, Francesca,Tagliapietra, Silvia,Berlier, Gloria,De Borggraeve, Wim M.,Cravotto, Giancarlo
supporting information, p. 2850 - 2860 (2021/05/06)
The use of copper(0) nanoparticles in the transfer semihydrogenation of alkynes has been investigated as a lead-free alternative to Lindlar catalysts. A stereo-selective methodology for the hydrogenation of internal alkynes to the corresponding (Z)-alkenes in high isolated yields (86% average) has been developed. This green and sustainable transfer hydrogenation protocol relies on non-noble copper nanoparticles for reduction of both electron-rich and electron-deficient, aliphatic-substituted and aromatic- substituted internal alkynes. Polyols, such as ethylene glycol and glycerol, have been proven to act as hydrogen sources, and excellent stereo- and chemoselectivity have been observed. Enabling technologies, such as microwave and ultrasound irradiation are shown to enhance heat and mass transfer, whether used alone or in combination, resulting in a decrease in reaction time from hours to minutes. (Figure presented.).
