Bülent Düz

Trapping of a cycloheptatetraene in the reaction of atomic carbon with phenol

Reaction of atomic carbon with phenol generates tropone in a reaction postulated to proceed via the hydroxycycloheptatetraenes, which rearrange to tropone. When the hydroxyphenylcarbenes are generated by the C atom deoxygenation of the corresponding aldehydes, the meta and para isomers produce tropone; the ortho isomer does not.

Electrochemically generated catalyst system with increased specificity and efficiency for olefin metathesis

Abstract A facile route for the electrochemical generation of an olefin metathesis catalyst from methylene chloride solution of WCl 6 was described. It was found that reductive, oxidative and pulse electrolysis produced the same intermediate. This electrolysis intermediate incorporates olefin into its structure possibly forming a metal–olefin complex, which decomposes into catalytically active metal carbene type species. ESCA, NMR and ESR methods were used to elucidate the structure of the catalyst system. The catalyst was applied in the metathesis of 1-octene and 2-octene without any need for a co-catalyst. Highly specific products with high yields were obtained.

DFT study of the 1-octene metathesis reaction mechanism with WCl6/C catalytic system.

A catalytic system consisting of tungsten carbene generated from WCl(6) and an atomic carbon is investigated theoretically for the metathesis of 1-octene at B3LYP/extended LANL2DZ level of DFT. The ground-state geometries and charge distributions of the structures belonging to the reaction mechanism are located. Energetics for the complete set of reactions, involving the formation of the tungsten carbene precatalyst, Cl(4)WCCl(2), the formation of tungsten methylidene and tungsten heptylidene with this precatalyst, and finally productive and degenerative metathesis steps with these alkylidene species are calculated in terms of total electronic energy and thermal energies. The free-energy (ΔG(298)) surfaces of the structures involved in the related reactions are constructed. In addition, solvent effects on the single point energies of the structures are investigated for two different solvents, namely, cyclohexane and chloroform. The results indicate that the formation of the catalytically active heptylidene is energetically favored in comparison to the formation of methylidene, while the degenerative and productive metathesis steps are competitive. In the catalytic cycle, the formation of ethylene is exothermic, while the formation of 7-tetradecene is endothermic. As expected, solvent effects on the metathesis reactions are minor and solvation does not cause any change in the directions of the overall metathesis reactions.

Study of the Stability and Activity of Electrochemically Produced Tungsten-Based Metathesis Catalyst with Symmetrical Alkenes

The olefin metathesis reaction has been carried out with many olefins of different types over various kinds of both homogeneous and heteregeneous catalysts [1, 2, 3]. The activity of a particular catalyst system depends on a number of factors, such as proportions of the components, the order in which the components are mixed, pretreatment procedures and reaction time [4]. Optimization of a given catalyst system by adjustment of the various parameters inturn can be quite a lengthy procedure.

ADMET Polymerization Activities of Electrochemically Reduced W-Based Active Species for Ge- and Sn-Containing Dienes

In the last 20 years metal atom-containing polymers have become important classes of polymers [1]. Properties like high thermic stability, electric, and photo conductometry make them very interesting for producing films, fibers, and coating [2]. Many of these compounds can be synthesized by conventional methods [3]. For producing metal-containing polymers anionic, cationic, and radicalic polymerizations were used [4–6]. Metal-containing polymers were also synthesized via acyclic diene metathesis (ADMET) polymerization that is facilitated by Schrock’s molybdenum alkylidene, or Grubbs’ ruthenium carbene catalyst [7–9]. In 1979, Gilet and coworkers succeeded in synthesizing metathetically active species from electrochemical reduction of WCl6 and MoCl5 [10,11]. In the light of these works, we have showed that electrochemically generated tungsten-based active species (WCl6-e–Al–CH2Cl2) catalyzes various metathesis-related reactions [12–16].

A Study on the Reactivity of WCl6–e––Al–CH2Cl2 with the Silicon-Containing Dienes

Although until the late 1980s very little information on effective metathesis conversion of organosilicon compounds had been reported, the use of molybdenum (Schrock) catalyst and ruthenium (Grubbs) carbene complexes as catalysts tolerating functional groups in substrates, have opened new synthetic opportunities in organosilicon chemistry. Silicon containing dienes undergo two types of metathetical transformation.

Intramolecular Trapping of Strained Bicyclic Allene in Carbon Atom Reactions

We report here the intermolecular trapping of endo-bicyclo[3.2.1]octa-2,3-dien-6-ol generated by reacting C with endo-bicyclo[2.2.1]hept-5-en-2-ol. The fragmentation reaction through endo-bicyclo[3.2.1]octa-2,3-dien-6-ol favours product (5Z)-octa-1,5dien-7-yn-3-ol rather than the intramolecular trapping product 2-oxatricyclo [4.2.1.03,8] non-4-ene. We also describe this reaction theoretically by means of the AM1 semiempirical method.

Reactions of Atomic Carbon with 2-Norbornene

Reaction of atomic carbon with 2-norbornene,1 generates octa-3,7-dien-1-yne, 5 in a reaction over bicyclo[3.2.1]octa-2,3-diene, 4 which fragments to 5. 4 has also been trapped by THF. The potential energy surfaces of C8H10 have been evaluated by means of the AMI semiempirical method.

Application of Uniform Macroporous Polystyrene Particles as Support in W(CO) 6 /CC14/hv Photocatalytic Olefin Metathesis System

Olefin metathesis has made a great impact in synthetic organic chemistry as a result of the preparation of many new polymers and valuable low molecular compounds. In this reactions, active species are metal carbenes that they can be generated in situ (classical systems) or added as well defined single components, which provide potential for enlarged application of metathesis in various fields[1]. Immobilization of the metathesis catalysts on solid supports will facilitate the work up and make the metahesis reactions more attractive for both pratical and industrial applications.

Acyclic Diene Metathesis (ADMET) Polymerization by Electrochemically Generated Tungsten-Based Active Catalyst System: Optimization of Reaction Conditions

Dienes can undergo olefin metathesis reactions of two types: (i) intermolecular, and (ii) intramolecular. Intramolecular metathesis (RCM) reactions occur with great readiness henever the product is a 6-membered ring. They are also often favoured for the production of 5-, 7-, and 8-membered rings, depending on the nature, number and location of any substituents. Intermolecular metathesis reactions lead eventually to high polymers and proceed very cleanly when initiated by metal carbene complexes; these are known as ADMET (acyclic diene metathesis) polymerizations (Figure 1). This class of polymerization reactions has been well established and comprehensively studied by Wagener and his group [1–6]. ADMET polymerization has been also a convenient route to linear polymers containing inorganic elements and functional groups for the preparation of new materials [7].