1657-53-0Relevant articles and documents
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.
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.
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.
Heteroleptic Copper-Based Complexes for Energy-Transfer Processes: E → Z Isomerization and Tandem Photocatalytic Sequences
Cruché, Corentin,Neiderer, William,Collins, Shawn K.
, p. 8829 - 8836 (2021/07/28)
Energy-transfer processes involving copper complexes are rare. Using an optimized heteroleptic copper complex, Cu(bphen)(XantPhos)BF4, photosensitized E → Z isomerization of olefins is demonstrated. The XantPhos ligand afforded sensitizers with improved catalyst stability, while the bphen ligand lengthened the excited-state lifetime. A series of 25 di- and trisubstituted alkenes underwent photoisomerization, including macrocycles and 1,3-enynes. Cu(bphen)(XantPhos)BF4 could also be employed in a tandem ATRA/photoisomerization process employing arylsulfonyl chlorides, an example of photoisomerization with halide-substituted olefins.
