İsmail Özdemir

Direct Arylation of Arene C−H Bonds by Cooperative Action of NHCarbene−Ruthenium(II) Catalyst and Carbonate via Proton Abstraction Mechanism

Direct functionalization of sp2 C−H bonds via ortho diarylation of 2-pyridyl benzene with arylbromides was achieved using ruthenium(II) catalysts containing a RuCl2(NHC) unit and generated from [RuCl2(arene)]2 and two types of NHC precursors, pyrimidinium and benzimidazolium salts, in the presence of Cs2CO3. DFT calculations from RuCl2(NHC)(2-pyridylbenzene) show that a proton abstraction mechanism, on cooperative actions of both the coordinated base and the Ru(II) center, is favored via a 13.7 kcal·mol-1 exothermic process affording an orthometalated intermediate with a 2.009 A Ru−C bond.

Synthesis and catalytic properties of N-functionalized carbene complexes of rhodium(I) and ruthenium(II)

Abstract Imidazolidin-2-ylidene derivatives of rhodium(I) and ruthenium(II), having 2-methoxyethyl substituent on the N-atom, [Rh(L)Cl(PPh3)2], [Rh(L)CI(COD)] or [Ru(L)Cl2(arene)] ( L 1 = CN ( Me ) CH 2 CH 2 N ︹ CH 2 CH 2 OMe and L 2 = CN ( CH 2 CH 2 OMe ) CH 2 CH 2 N ︹ CH 2 CH 2 OMe ) have been prepared by treatment of [RhCl(PPh3)3], [RhCI(COD)]2 or [RuCl2(arene)]2 with the N-functionalized electron-rich olefins L1 = L1 or L2 = L2. All of the new carbene rhodium(I) or ruthenium(II) complexes have proved to be effective catalysts for the cyclopropanation reactions of diazoalkane derivatives with styrene and the rhodium(I) precursors lead to the highest catalytic activity.

First ruthenium complexes with a chelating arene carbene ligand as catalytic precursors for alkene metathesis and cycloisomerisation

Electron-rich carbene precursors 2 and 3, containing the imidazolidin-2-ylidene moiety with one (2) and two (3) pendent N-(2,4,6-trimethylbenzyl) groups, on reaction with [RuCl2(arene)]2 lead to ruthenium(II) complexes 5 and 6 containing the chelating 8-electron mixed arene–carbene ligand; the X-ray diffraction crystal structure of RuCl2{η1-CN[CH2( η6-2,4,6-Me3C6H2)]CH2CH2N(CH2CH2OMe)} 6, was established. These complexes are precursors of the unstable ruthenium-allenylidene intermediates 7 and 8, but are active catalysts either for selective catalytic alkene metathesis or cycloisomerization, depending on the nature of the 1,6-diene.

Synthesis of a water-soluble carbene complex and its use as catalyst for the synthesis of 2,3-dimethylfuran

Abstract 1,1′,3,3′-Tetrakis(p-dimethylaminobenzyl)-2,2′-biimidazolidinylidene, L2R (R=CH2C6H4NMe2-p) which contains four peripheral NMe2 substituents, was obtained from 4-dimethylaminobenzaldehyde by a three-step reaction sequence, and was used for the preparation of imidazolidin-2-ylidene Ru(II) and Rh(I) complexes 1 and 2. Etherial HCl readily protonates the NMe2 functionality on the carbene ligand of 1 to give the corresponding salt, 1′; whereas the reaction of 2 with HCl gave a hygroscopic and ill-defined rhodium species. In aqueous solution the salt 1′ is an efficient and active catalyst for intramolecular cyclisation of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran. The catalyst 1′ could be recovered by simple phase separation and the catalytic reaction was maintained for five different runs. All of the new compounds were characterised by elemental analyses, IR and NMR spectroscopy and the molecular structure of 1 was determined by X-ray crystallography.

Ruthenium-carbene catalysts for the synthesis of 2,3-dimethylfuran

Abstract A variety of neutral arene-ruthenium-carbenes of type (arene)RuCl 2 (= C(NR)CH 2 CH 2 N R) have been used for the catalytic transformation of ( Z )-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran. The catalytic reaction takes place at 80°C with mononuclear complexes III–V to afford the furan in ∼ 90% yield. The binuclear catalysts VIa and VIIa having a linked bis-carbene bridge operate at room temperature to initiate an exothermic reaction offering 90–97% of furan.

Synthesis and immobilization of N-heterocyclic carbene complexes of Ru(II): catalytic activity and recyclability for the furan formation

Abstract Synthesis, characterization and immobilization of ruthenium(II) complexes of the type [RuCl 2 L(η 6 -arene)] (L= , arene= p -cymene, 3 and arene=C 6 Me 6 , 4 ) and [RuCl 2 L] (L=η 1 -carbene-η 6 -arene bidentate ligand, ), 5 , morphologically different silicas by sol–gel method are described and their reactivity and recyclability in the furan formation were also reported.

Suzuki–Miyaura Reaction of Unactivated Aryl Chlorides Using Benzimidazol‐2‐Ylidene Ligands

Abstract Four functionalized bis(benzimidazolium) salts (2a–d) have been prepared and characterized by conventional spectroscopic methods and elemental analyses. A highly effective, easy to handle, and environmentally bengin process for palladium‐mediated Suzuki cross‐coupling was developed. The in situ prepared three‐component system Pd(OAc)2/bis(benzimidazolium) bromides (2a–d) and Cs2CO3 catalyzes quantitatively the Suzuki cross‐coupling of deactivated aryl chloride in aqueous media.

N-Heterocyclic carbene–palladium catalysts for the direct arylation of pyrrole derivatives with aryl chlorides

Summary New Pd–NHC complexes have been synthesized and employed for palladium-catalyzed direct arylation of pyrrole derivatives by using electron-deficient aryl chlorides as coupling partners. The desired coupling products were obtained in moderate to good yields by using 1 mol % of these air-stable palladium complexes. This is an advantage compared to the procedures employing air-sensitive phosphines, which have been previously shown to promote the coupling of aryl chlorides with heteroarenes.

Synthesis and characterization of N-heterocyclic carbene palladium complex and its application on direct arylation of benzoxazoles and benzothiazoles with aryl bromides

A mixed-halogen bis(1-(4-tert-butylbenzyl)-3-(2, 4, 6-trimethylbenzyl)-1H-benzo[d]imidazol-2-ylidene) palladium(II) complex, trans-[Pd(Cl0.7Br0.3)2(C28H32N2)2], has been synthesized and characterized by elemental analysis, 1H-NMR, 13C-NMR, and IR spectroscopy, and single crystal X-ray diffraction. The palladium in the mononuclear complex is four-coordinate in a square-planar configuration with two carbenes of two benzo[d]imidazole rings and two halides. The two halides are disordered between Br and Cl, with the Cl: Br ratio approximately 0.7 : 0.3. The angles C1–Pd1–Br1, 88.63(11)° and C1i–Pd1–Br1i, 91.37(11)° (i: 1−x, 1−y, 1−z) in the coordination sphere are very close to the ideal value of 90°. The Pd–X distance is slightly longer than other carbene derivative Pd–Cl single bond distances and slightly shorter than Pd–Br single bond distances. These results agree with the Cl/Br disorder at the halogen position. The palladium–carbene complex was tested as a catalyst in the direct arylation reaction of benzoxazoles and benzothiazoles with aryl bromides.

Synthesis, characterization and catalytic activity of novel N-heterocyclic carbene-palladium complexes

The reaction of Pd(OAc)2 with 1-(benzhydryl)-3-(alkyl)benzimidazolium salts 1a-d yields trans-bis[1-(benzhydryl)-3-(alkyl)benzimidazolin-2-ylidene]dibromopalladium(II) complexes (2a-d) which were characterized by elemental analysis, NMR spectroscopy and the molecular structures of 2b, and 2d were determined by X-ray crystallography. The catalytic activity of PdBr2bis(benzimidazolin-2-ylidene) complexes 2a-d was evaluated in the direct arylation reaction of benzothiazole with bromobenzene derivatives.