Palladium(ii) catalyzed thiono-thiolo rearrangement of propargyl thionophosphates

Palladium(II) effectively catalyzes the [3,3]-sigmatropic type rearrangement of propargyl thionophosphates to provide allenyl thiolophosphates specifically.     

Palladium(0) catalyzed enantioselective rearrangement of O-allylic thiocarbamates to S-allylic thiocarbamates: asymmetric synthesis of allylic thiols

The Pd(0) catalyzed rearrangement of the O-allylic thiocarbamates rac-2a, rac-2b and rac-4 in the presence of the chiral bisphosphane 5 proceeded quantitatively and gave the S-allylic thiocarbamates 6a, 6b and 7, respectively, with 91, 92 and 97% ee, respectively, in high yields. Saponification of the S-allylic thiocarbamate 7 furnished the allylic thiol 9 with 97% ee.     

钯配合物催化的亚磺酸烯丙酯重排反应

在杂原子酸烯丙酯和低价过渡金属配合物反应的系统研究中,我们发现在四(三苯膦)钯韵催化下,亚磺酸烯丙酯能够容易地重排成相应的砜.反应温度要比相应的热重排低得多,而且时间短,产率高. 重排反应的典型实例如下:在25℃氩气气氛下,向溶有91mg(0.5mmol)苯基亚磺酸烯丙基酯(1a)的5mL四氢呋喃溶液中加入25mg(0.022mmol)四(三苯膦)钯,搅拌反应混合物,薄层层析跟踪直至原料消失,耗时约70分钟.减压除去四氢呋喃,残渣用四氯化碳萃取,硅胶制备薄层层析分离[5:1石油醚(30～60℃)-乙酸乙酯],得79mg油状物,产率87％,b.p.130℃(浴温)/0.2 mm(文献值:111～113℃/0.25mm).结果如表1所示.     

Palladium(0) catalyzed reaction of 1,3-diene 1,4-epiperoxides

Reaction of 1,3-diene 1,4-epiperoxides with Pd(PPh₃)₄ catalyst forms the corresponding 4-hydroxy enones, syn diepoxides, and 1,4-diols as the major products. The results are interpreted as being due to competing Pd(0)/Pd(II) and Pd(0)/Pd(I) exchange mechanisms.     

Palladium catalyzed thiono-thiolo allylic rearrangement of o-allyl phosphoro- and phosphonothionates

A new thiono-thiolo allylic rearrangement of phosphoro- and phosphono-thionates with Pd(PPh₃)₄ catalyst is described, where a variety of thionates are converted to the corresponding thiolates in excellent yields.     

Anionic Palladium(0) and Palladium(II) Ate Complexes

Palladium ate complexes are frequently invoked as important intermediates in Heck and cross‐coupling reactions, but so far have largely eluded characterization at the molecular level. Here, we use electrospray‐ionization mass spectrometry, electrical conductivity measurements, and NMR spectroscopy to show that the electron‐poor catalyst [L₃Pd] (L=tris[3,5‐bis(trifluoromethyl)phenyl]phosphine) readily reacts with Br⁻ ions to afford the anionic, zero‐valent ate complex [L₃PdBr]⁻. In contrast, more‐electron‐rich Pd catalysts display lower tendencies toward the formation of ate complexes. Combining [L₃Pd] with LiI and an aryl iodide substrate (ArI) results in the observation of the Pd^II ate complex [L₂Pd(Ar)I₂]⁻.     

Palladium(0) nanoparticle catalyzed cross-coupling of allyl acetates and aryl and vinyl siloxanes

The cross-coupling of allyl acetates and aryl and vinyl siloxanes proceeds readily by the catalysis of in situ generated palladium(0) nanoparticles. The reactions are stereoselective, and (E)-coupling products are obtained both from cis and trans allyl acetates. The coupling with vinyl siloxanes provides a novel protocol for the synthesis of 1,4-pentadienes.     

Palladium(0) catalyzed regioselective carbonyl propargylation across tetragonal tin(II) oxide via redox transmetallation

Facile homopropargylation of aldehydes by propargyl bromides over tetragonal tin(II)oxide and catalytic palladium(0) occurs which is proposed to involve the prior formation of dinuclear allenylpalladium followed by redox transmetallation to beta-SnO.     

Palladium(0)catalyzed reactions of propargylic carbonates and dialkyl cycloalkanone-α,α-dicarboxylates

Propargylic carbonates reacted with dialkyl cycloalkanone-α,α′-dicarboxylates under thecatalysis of Pd(0)complex to give bicyclic compounds in high yields.The two electron-withdrawinggroups at α and α′positions of cycloalkanone rings are essential for the annulation reaction.     

Palladium(II) catalyzed allylic rearrangement: Stereoselective synthesis of 2-substituted (e)-β acetoxy (or benzoyloxy)ethylidenecyclohexanes

Diastereomeric mixtures of 2-substituted 1-vinyclyclohexyl acetates (or benzoates) are rearranged stereoselectively to 2-substituted (E)-β-acetoxy(or benzoyloxy)ethylidenecyclohexanes by the catalysis of bis(acetonitrile)palladium(II) chloride. A mechanism related to the stereoselectivity and reactivity is discussed in terms of the conformational requirements in a transition state.     

Palladium(II) catalyzed cyclization of alkynoic acids

Under the catalytic action of palladium(II) in the presence of triethylamine, 3-, 4-, and 5-alkynoic acids afford 3-buten-4-olides, 4-penten-4-olides, and 5-hexen-5-olide, respectively, in good to excellent yields.     

N-acyliminium ions: detection of a hidden 2-aza-cope rearrangement

A 2-aza-Cope rearrangement underlying the more typical reactions of N-acyl-2-aza-1,5-hexadienes has been detected using triethylsilane as an acyliminium ion trap.     

Palladium(0)-catalyzed cycloisomerization of enallenes

A novel palladium(0)-catalyzed cycloisomerization of enallenes has been developed. This reaction, catalyzed by [Pd(dba)2] (dba=dibenzylideneacetone) in acetic acid, results in the formation of cyclopentene derivatives and [n.3.0]bicyclic systems (n=3, 4) in good to high yields. The carbon-carbon bond-forming step is highly stereoselective to give cis-fused bicyclic systems. The presence of acetic acid as solvent and dba as ligand for palladium(0) turned out to be essential for the reaction in order to provide good reactivity and regioselectivity.     

Interaction of Dinitrogentrioxide with Platinum(0) and Palladium(0) Complexes

Dinitrogentrioxide reacts with tetrakis(triphenylphosphine) platinum and palladium under nitrogen to give dinitrobis(triphenylphosphine) platinum(II) and palladium(II) complexes, respectively. In the presence of oxygen these reactions afford the formation of nitro-nitrato complexes of platinum(II) and palladium(II). The products are characterized by the elemental analyses, i.r. spectra, conductivity and magnetic measurements.     

Palladium(II)-catalyzed claisen rearrangement of allyl vinyl ethers

The Claisen rearrangement of allyl vinyl ethers is catalyzed by PdCl₂(CH₃CN)₂, provided that alkyl substituents protect the vinyl ether double bond from coordination by the metal catalyst.     

Palladium catalyzed Heck-Mizoroki and Suzuki-Miyaura coupling reactions (Review)

This article is about the progress of palladium compounds as a catalyst for Heck-Mizoroki and Suzuki-Miyaura coupling reactions. Industrial catalysts with broad applicability need continuous catalyst development process through modification of ligand design, geometry and functionality. Recently catalysts have been synthesized through attachment of the activated palladium complexes on the surface of polymer support, particularly, insoluble in reaction medium. An appropriate mixture of palladium salt and ligand is also used as an important modification in some cases to get better results. We surveyed the important palladium compounds synthesized up to early 2014 for Heck-Mizoroki and Suzuki-Miyaura coupling reactions and summarize their progress in terms of ligand modification and other associated parameters.     

Palladium catalyzed cyanation of o-dichloroarenes with potassium hexacyanoferrate(ii)

Cyanation of o-dichloroarenes with potassium hexacyanoferrate(ii) catalyzed by Pd(OAc)₂/PPh₃ system gave the corresponding phthalodinitriles in moderate yields. The method of competitive reactions revealed that activation rate of chloroarenes by Pd-catalyst increased in the presence of the electron-withdrawing groups in the arene core.