Sedat Yaşar

Palladium-Catalyzed Heck Coupling Reaction of Aryl Bromides in Aqueous Media Using Tetrahydropyrimidinium Salts as Carbene Ligands

An efficient and stereoselective catalytic system for the Heck cross coupling reaction using novel 1,3-dialkyl-3,4,5,6-tetrahydropyrimidinium salts (1, LHX) and Pd(OAc)2 loading has been reported. The palladium complexes derived from the salts 1a-f prepared in situ exhibit good catalytic activity in the Heck coupling reaction of aryl bromides under mild conditions.

Hydrogenation of Acetophenone and Its Derivatives with 2-Propanol Using Aminomethylphosphine-Ruthenium Catalysis

The reaction of 3′-aminopropyltriethoxysilane with the phosphonium salt ([Ph2P(CH2OH)2]Cl) gives an aminomethylphosphine-type ligand ((CH3CH2O)3Si(CH2)3N(CH2PPh2)2). Reaction of the ligand ((CH3CH2O)3Si(CH2)3N(CH2PPh2)2) with silica gives silica supported aminomethylphosphine ligand (SiO2)-O-Si(CH2)3N(CH2PPh2)2). The ligands were refluxed with [RuCl2(p-cymene)]2 in toluene to give [RuCl2((CH3CH2O)3Si(CH2)3N(CH2PPh2)2)] and silica-supported SiO2)-O-[RuCl2((Si(CH2)3N(CH2PPh2)2)2] complex, respectively. The catalytic studies show that the complexes [RuCl2((CH3CH2O)3Si(CH2)3N(CH2PPh2)2)] and SiO2)-O-[RuCl2((CH3CH2O)3Si(CH2)3N(CH2PPh2)2)2] are very active catalysts for the transfer hydrogenation of acetophenone by 2-propanol in basic media. The best yield was observed in hydrogenation of m-methoxy acetophenone (95%) with catalyst [RuCl2((CH3CH2O)3Si(CH2)3N(CH2PPh2)2)].

Polyimide-Supported Dichloro-1,3-bis(p-dimethylaminobenzyl)benzimidazolidin-2-ilidenruthenium (II) as Effective Catalyst for Hydrosilylation Reactions

The present study relates to a heterogeneous polyimide-supported transition metal complex catalyst for hydrosilylation reactions, which is prepared by functionalizing a heat- and acid-resistant polyimide resin with a homogeneous metal catalyst of ruthenium (II) complex. The heterogeneous polyimide-supported transition metal complex catalyst of the invention provides superior catalytic activity, selectivity and stability in the hydrosilylation of acetophenone. Further, the catalyst has strong resistance against heat and acid. Besides, the catalyst of the invention may provide the following advantage which are critical in industrial use: it can be easily separated from the reaction product, which eases recycling of the catalyst.

Ring-expanded iridium and rhodium N-heterocyclic carbene complexes: a comparative DFT study of heterocycle ring size and metal center diversity

Abstract A new series of ring-expanded six- and seven-membered N-heterocyclic carbene precursors (re-NHCs) and their transition metal complexes were synthesized. The basic properties of the synthesized materials were investigated by density functional theory (DFT). The six- and seven-membered re-NHCs were synthesized in good yield via reaction of the corresponding alkyldibromides or alkyldiiodides with N,N′-bis-(2-phenylbenzene)formamidine in the presence of K2CO3 under aerobic conditions. Complexes, represented by the formula [ML1,2(COD)Cl] (where M = Ir or Rh and L is a ring-expanded N-heterocyclic carbene ligand), were synthesized in the presence of the corresponding free carbene and iridium or rhodium metal precursors in tetrahydrofuran. All new re-NHC complexes were characterized by different analytical techniques, including NMR spectroscopy, X-ray diffraction, UV spectroscopy and elemental analysis. According to molecular electrostatic potential calculations, the electrophilic properties of the complexes were aligned, from highest to lowest, as Ir-6-DiPh, Rh-6-DiPh and Ir-7-DiPh. The HOMO, LUMO and energy gaps of the complexes were calculated by DFT. On the basis of the DFT analysis, it can be predicted that Rh-6-DiPh is the most stable complex and Ir-7-DiPh is more reactive than Ir-6-DiPh.

Dichlorido[1-(2-methyl­benz­yl)-3-(η6-2,4,6-trimethyl­benz­yl)-1H-2,3-dihydro­benzimidazol-2-yl­idene]ruthenium(II) dichloro­methane solvate

The title complex, [RuCl2(C25H26N2)]·CH2Cl2, is best thought of as containing an octahedrally coordinated Ru center with the arene occupying three sites. Two Ru—Cl bonds and one Ru–carbene bond complete the distorted octahedron. The carbene portion of the ligand is a benzimidazole ring. This ring is connected to the C6H2(CH3)3 arene group by a CH2 bridge. This leads to a system with very little apparent strain. A dichloromethane solvent molecule completes the crystal structure. Further stabilization is accomplished via C—H⋯N and C—H⋯Cl interactions.

A Palladium Catalyst System for the Efficient Cross-Coupling Reaction of Aryl Bromides and Chlorides with Phenylboronic Acid: Synthesis and Biological Activity Evaluation

New benzimidazolium salts 1a–c and their palladium bis-N-heterocyclic carbene complexes 2a–c and palladium PEPPSI-type complexes 3a–c were designed, synthesized and structurally characterized by NMR (1H and 13C), IR, DART-TOF mass spectrometry and elemental analysis. Then these complexes 2–3 were employed in the Suzuki-Miyaura cross-coupling reaction of substituted arenes with phenylboronic acid under mild conditions in toluene and DMF/H2O (1/1) to afford functionalized biaryl derivatives in good to excellent yields. The antibacterial activity of palladium bis-N-heterocyclic carbene complexes 2a–c and palladium PEPPSI-type complexes 3a–c was measured by disc diffusion method against Gram positive and Gram negative bacteria. Compounds 2a, 2c and 3a–c exhibited potential antibacterial activity against four bacterial species among the five used indicator cells. The product 2b inhibits the growth of the all five tested microorganisms. Moreover, the antioxidant activity determination of these complexes 2–3, using 2.2-diphenyl-1-picrylhydrazyl (DPPH) as a reagent, showed that compounds 2a–c and 3b possess DPPH antiradical activity. The higher antioxidant activity was obtained from the product 2b which has radical scavenging activity comparable to that of the two used positive controls (gallic acid “GA“ and tutylatedhydroxytoluene “BHT“). Investigation of the anti-acetylcholinesterase activity of the studied complexes showed that compounds 2b, 3a, and 3b exhibited moderate activity at 100 μg/mL and product 2b is the most active.

1-(2-Phenyl-benz-yl)-3-(2,4,6-trimethyl-benz-yl)imidazolidinium bromide.

In the title salt, C26H29N2 +·Br−, which may serve as a precursor for N-heterocyclic carbenes, the imidazolidine ring adopts a twist conformation with a pseudo-twofold axis passing through the N—C—N carbon and the opposite C—C bond. The N—C—N bond angle [113.0 (4)°] and C—N bond lengths [1.313 (6) and 1.305 (6) Å] confirm the existence of strong resonance in this part of the molecule. In the crystal, a C—H⋯Br interaction is present. The dihedral angle between the biphenyl rings is 64.3 (2)° and the phenyl rings make angles of 76.6 (3) and 18.5 (3)° with the plane of the imidazolidine ring.

N-Heterocyclic carbene-Pd(II)-PPh3 complexes as a new highly efficient catalyst system for the Sonogashira cross-coupling reaction: Synthesis, characterization and biological activities

Abstract A novel series of N-heterocyclic carbene-phosphine palladium(II) complexes has been synthesized and fully characterized by IR, 1H NMR, 13C NMR, and 31P NMR spectroscopies, and elemental analysis. The new N-heterocyclic carbene (NHC)-phosphine palladium(II) complexes 3a–h have been easily prepared by the reaction of the corresponding PEPPSI (pyridine-enhanced precatalyst preparation stabilization and initiation) complexes 2a–h and triphenylphosphine in dichloromethane in high yields. These complexes were applied as catalyst precursors which efficiently catalyzed Sonogashira reactions between aryl bromides and phenylacetylene to afford the corresponding products in good yields. The bulky NHC-Pd-PPh3 complexes 3 were tested against Gram-positive and Gram-negative bacteria to study their biological activity. All the complexes exhibit antibacterial against these organisms. Investigation of the anti-acetylcholinesterase activity of the studied complexes showed that compounds 3a and 3b exhibited moderate activity at 100 μg mL−1 and product 3b is the most active.

1,3-Bis(4-tert-butyl­benz­yl)-4,5-dihydro­imidazolium chloride monohydrate

In the title compound, C25H35N2 +·Cl−·H2O, the imidazolidine ring adopts a twisted conformation, with a pseudo-twofold axis passing through the N—C—N carbon and the opposite C—C bond. The N—C—N fragment of the imidazolidine ring shows some degree of both double- and single-bond character due to partial electron delocalization. One of the tert-butyl groups is disordered over two conformations with occupancies of 0.714 (8) and 0.286 (8). In the crystal, O—H⋯Cl and C—H⋯O hydrogen bonds help to establish the packing.