Pd‐catalyzed direct CH cyanation of picolinamides via bidentate chelation assistance

A bidentate‐chelation assistant palladium‐catalyzed direct C‐H cyanation of picolinamides with TMSCN is described. The reaction of various derivatives gave the corresponding cyanated products in moderate to good yields under mild conditions. In addition, the cyanated product could transform into some valuable functional groups in good yields. Copyright © 2016 John Wiley & Sons, Ltd.     

Palladium‐catalyzed cyanation reaction of aryl halides using K4[Fe(CN)6] as non‐toxic source of cyanide under microwave irradiation

An efficient method for preparation of aryl nitriles—using [Pd{C₆H₂(CH₂CH₂ NH₂)‐(OMe)₂,3,4} (µ‐Br)]₂ complex as an efficient catalyst and K₄[Fe(CN)₆] as a green cyanide source—from aryl bromides, aryl iodides and aryl chlorides under microwave irradiation has been reported. This complex has been demonstrated to be an active and efficient catalyst for this reaction. Using a catalytic amount of this synthesized palladium complex in DMF at 130 °C led to production of the cyanoarenes in excellent yields in short reaction times. Copyright © 2010 John Wiley & Sons, Ltd.     

Heck reactions of aryl halides with alk‐1‐en‐3‐ol derivatives catalysed by a tetraphosphine–palladium complex

cis,cis,cis‐1,2,3,4‐Tetrakis(diphenylphosphinomethyl)cyclopentane–[PdCl(C₃H₅)]₂ efficiently catalyses the Heck reaction of alk‐1‐en‐3‐ol with a variety of aryl halides. In the presence of hex‐1‐en‐3‐ol or oct‐1‐en‐3‐ol, the β‐arylated carbonyl compounds were selectively obtained. Turnover numbers up to 84 000 can be obtained for this reaction. Linalool and 2‐methylbut‐3‐en‐2‐ol led regio‐ and stereoselectively to the corresponding (E)‐1‐arylalk‐1‐en‐3‐ol derivatives. A minor electronic effect of the substituents of the aryl bromide was observed. Quite similar reaction rates were generally observed in the presence of activated aryl bromides such as bromoacetophenone and deactivated aryl bromides such as bromoanisole, indicating that, with these alkenols and this catalyst, the oxidative addition of aryl bromides to palladium is not the rate‐limiting step. It should be noted that this reaction also proceeds with sterically very congested aryl bromides such as 9‐bromoanthracene or 2,4,6‐triisopropylbromobenzene or with a vinyl bromide. On the other hand, low yields were obtained with aryl chlorides. Copyright © 2006 John Wiley & Sons, Ltd.     

A phosphine‐free heterogeneous Suzuki–Miyaura reaction of aryl bromides catalyzed by MCM‐41‐supported tridentate nitrogen palladium complex under air

MCM‐41‐supported tridentate nitrogen palladium(II) complex [MCM‐41‐3 N‐Pd(II)] was conveniently synthesized from commercially available and cheap 3‐(2‐aminoethylamino)propyltrimethoxysilane via immobilization on MCM‐41, followed by reacting with pyridine‐2‐carboxaldehyde and PdCl₂. It was found that this palladium complex is an excellent catalyst for the Suzuki–Miyaura coupling reaction of aryl bromides on two points: (i) the use of 5 × 10⁻⁴ mol equiv. of MCM‐41‐3 N‐Pd(II) under air afforded the coupling products efficiently after easy workup; (2) the catalyst can be reused many times without loss of catalytic activity. Copyright © 2011 John Wiley & Sons, Ltd.     

Efficient cyanation of aryl bromides with K4[Fe(CN)6] catalyzed by a palladium-indolylphosphine complex

This study describes a general palladium-catalyzed cyanation of aryl bromides using K₄[Fe(CN)₆] as the cyanide surrogate. The reactions can be successfully conducted under mild reaction conditions (at 50 °C) in mixed solvents (water/MeCN = 1:1) without any surfactant additives, and afford the desired aryl nitriles in good-to-excellent yields. Particularly noteworthy is that this system allows the mildest reaction temperature reported so far for palladium-catalyzed cyanation of aryl bromides with K₄[Fe(CN)₆] source in general. Common functional groups, including keto, aldehyde, free amine, and heterocyclic substrates are compatible under this system. Interestingly, the phosphine ligands bearing -PCy₂ moiety, which usually show excellent activity in aryl halide couplings, are found less effective than the corresponding ligands with -PPh₂ group.     

Pd/C: A Recyclable Catalyst for Cyanation of Aryl Halides with K4[Fe(CN)6]

Aryl nitriles have been prepared from the corresponding aryl halides with potassium hexacyanoferrate(II) using Pd/C as a catalyst. No ligand or cocatalyst is required. This protocol also avoids the use of highly toxic alkali cyanides. Furthermore, the catalyst can be recycled via simple filtration and washing sequences.     

Suzuki–Miyaura coupling reactions of aryl chlorides catalyzed by a new nickel(II) σ‐aryl complex

A new nickel(II) σ‐aryl complex, trans‐chloro(9‐phenanthrenyl)bis(triphenylphosphine)nickel(II), was used as a precatalyst for the Suzuki–Miyaura coupling reactions of aryl chlorides. The catalytic conditions were optimized by investigating the cross‐coupling of p‐chloroanisole with phenylboronic acid. The results show that this complex is efficient for both electron‐rich and electron‐deficient aryl chlorides, though it gives better yields for activated arylboronic acids than deactivated ones. All isolated cross‐coupled biaryl products have been characterized by ¹H and ¹³C NMR, and their spectral data are consistent with those reported. Side products from the coupling of arylboronic acid with the precatalyst complex have also been isolated and characterized, which is helpful for understanding the coupling mechanism. Copyright © 2013 John Wiley & Sons, Ltd.     

Über Oxide mit dem “Butterfly-Motiv”: Rb6[Fe2O5] und K6[Fe2O5]

New Oxides with the “Butterfly-Motive”: Rb₆[Fe₂O₅] and K₆[Fe₂O₅] Rb₆[Fe₂O₅] and K₆[Fe₂O₅] were obtained for the first time by annealing intimate mixtures of “Rb₆CdO₄” with CdO (molar ratio 1 : 1.1) and KO_0.48 with CdO (molar ratio 5.9 : 1) respectively in closed Fe-cylinders. Determination and refinement of the crystalstructure confirms the space group C2/m (four-circle-diffractometer data). Rb₆[Fe₂O₅]: Ag Kα , 720 out of 1220 Io(hkl), R = 9.68%, R_w = 6.09%; a = 718.9pm, b = 1183.1 pm, c = 695.4pm, β = 95.05°, Z = 2; K₆[Fe₂O₅]: MoKα , 1214 Out of 12141_o(hkl), R = 3.20070, R_w = 2.48%, a = 691.21 pm, b = 1142.78pm, c = 665.50pm, β = 93.82°, Z = 2. The binuclear unit [O₂FeOFeO₂]^6? already known to be planar with oxoferrates(II) now was observed to be angular here and closely related to Na₆[Be₂O₅].     

Microwave-enhanced and ligand-free copper-catalyzed cyanation of aryl halides with K4[Fe(CN)6] in water

Copper-catalyzed cyanation of aryl halides was improved to be more economical and environmentally friendly by using water as the solvent and ligand-free Cu(OAc)₂·H₂O as the catalyst under microwave heating. The suggested methodology was applicable to a wide range of substrates including aryl iodides and activated aryl bromides.     

KCa(H2O)2[FeIII(CN)6]⋅H2O Nanoparticles as an Antimicrobial Agent against Staphylococcus aureus

Biocompatible nanoparticles based on a calcium analogue of Prussian blue were designed and synthesized to take advantage of their ability to penetrate the cell membrane in Staphylococcus aureus and to undergo selective ion exchange with intracellular iron to disrupt iron metabolism in such pathogenic bacteria for antibacterial applications. KCa(H₂O)₂[Fe^III(CN)₆]?H₂O nanoparticles penetrate the bacterial cell membrane and sequester intracellular iron by ion exchange to form insoluble Prussian blue, thus inhibiting bacterial growth.     

A Mixed-Valence and Mixed-Spin Molecular Magnetic Material: [MnIIL]6[MoIII(CN)7][MoIV(CN)8]2⋅19.5 H2O

Long-range ferromagnetic ordering at 3 K is observed for the title compound, which may be considered as a fully localized mixed-valence species (Mo³⁺ and Mo⁴⁺) as well as a mixed-spin species (low-spin and high-spin Mn²⁺ ions). Its two-dimensional structure consists of heart-shaped 48-membered rings, and each ring contains 16 metal centers (see picture).     

Efficient construction of C–C bonds from aryl halides/aryl esters with arylboronic acids catalysed by palladium(II) thiourea complexes

A new set of palladium(II) complexes comprising phenyl(thiazolyl)thiourea ligands have been successfully synthesized and characterized with the aid of analytical as well as spectral (IR, UV–visible and NMR) methods. A distorted square‐planar geometry with N^S coordination mode of thiourea ligands in the new palladium complexes was corroborated by single‐crystal X‐ray diffraction methods. Interestingly, the palladium(II) thiourea complexes showed the highest catalytic activity with 0.1 mol% catalyst loading in Suzuki–Miyaura cross‐coupling reactions utilizing a range of aryl bromides/unactivated aryl chlorides with arylboronic acids as coupling partners in aqueous–organic media. Syntheses of diaryl ketones using aryl esters and arylboronic acids as coupling partners were also achieved with low catalyst loading within 20 h. The potential of our catalyst was demonstrated by its wide substrate scope, low catalyst loadings and high isolated yield. Moreover, the influences of key parameters like solvent, base, temperature and catalyst loading were also investigated.     

The Prominent Enhancing Effect of the Cation–π Interaction on the Halogen–Hydride Halogen Bond in M1⋅⋅⋅C6H5X⋅⋅⋅HM2

We designed M¹???C₆H₅X???HM² (M¹=Li⁺, Na⁺; X=Cl, Br; M²=Li, Na, BeH, MgH) complexes to enhance halogen–hydride halogen bonding with a cation–π interaction. The interaction strength has been estimated mainly in terms of the binding distance and the interaction energy. The results show that halogen–hydride halogen bonding is strengthened greatly by a cation–π interaction. The interaction energy in the triads is two to six times as much as that in the dyads. The largest interaction energy is ?8.31 kcal mol^?1 for the halogen bond in the Li⁺???C₆H₅Br???HNa complex. The nature of the cation, the halogen donor, and the metal hydride influence the nature of the halogen bond. The enhancement effect of Li⁺ on the halogen bond is larger than that of Na⁺. The halogen bond in the Cl donor has a greater enhancement than that in the Br one. The metal hydride imposes its effect in the order HBeH<HMgH<HNa<HLi for the Cl complex and HBeH<HMgH<HLi<HNa for the Br complex. The large cooperative energy indicates that there is a strong interplay between the halogen–hydride halogen bonding and the cation–π interaction. Natural bond orbital and energy decomposition analyses indicate that the electrostatic interaction plays a dominate role in enhancing halogen bonding by a cation–π interaction.