Olefins cyclooctene

C albeit with reactive olefins (cyclooctene and cyclohexene). Cyclohexene afforded mixtures of epoxide, cyclohexane-1,2-diol, and ally lie oxidation products. 

Rhodium-NHC complexes [Rh( <-Cl)(IPr)( -olefin)]2 and RhCl(IPr)(py)(t/"-olefin) (IPr= l,3-bis(2,6-diisopropylphenyl)imidazol-2-carbene, py = pyridine, olefin = cyclooctene) have been designed as highly active catalysts for hydrothiolation of alkynes RC=CH with R SH. The dinuclear catalyst was found to promote the formation of the linear product RCH=CHSR, whereas the mononuclear catalyst favoured the branched isomer R(R S)C=CH2- A complex interplay between electronic and steric effects exerted by the carbene (IPr), pyridine, and hydride ligands accounts for the observed regioselectivity. DFT calculations suggested that migratory insertion of the alkyne into the rhodium-thiolate bond is the rate-determining step. ... 

Catalytic cyclopropanation of alkenes has been reported by the use of diazoalkanes and electron-rich olefins in the presence of catalytic amounts of pentacarbonyl(rj2-ris-cyclooctene)chromium [23a,b] (Scheme 6) and by treatment of conjugated ene-yne ketone derivatives with different alkyl- and donor-substituted alkenes in the presence of a catalytic amount of pentacarbon-ylchromium tetrahydrofuran complex [23c]. These [2S+1C] cycloaddition reactions catalysed by a Cr(0) complex proceed at room temperature and involve the formation of a non-heteroatom-stabilised carbene complex as intermediate. 

Addition of TCS 14 to CH2l2/Zn, which contains up to 0.04 mol% of lead impurity, improves the Simmons-Smith reaction of olefins such as cyclooctene to give up to 96% of the cyclopropane 2103 [36] (Scheme 13.12). 

Fig. 3.31 Steric control in alternating ROMP Tendencies of norbomene and cyclooctene to give productive olefin metathesis upon coordination are illustrated by a thick arrow (preferred monomer) or a thin arrow (less favoured monomer) (a) only minor steric hindrance SlMes greatly favours the polymerisation of the strained norbomene (b) the rotating phenylethyl-group induces a steiically more congested active site, leading to preferred incorporation of the smaller cyclooctene (c) the flexible and small cyclooctene derived polymer fragment permits the incorporation of the bulky norbomene...

An obvious method to investigate the formation and the nature of the catalytically active nickel species is to study the nature of products formed in the reaction of complexes such as 3 or 4 with substrate olefins. This has been investigated in some detail in the case of the catalytic dimerization of cyclooctene to 1-cyclooctylcyclooctene (17) and dicy-clooctylidene (18) [Eq. (4)] using as catalyst 7r-allylnickel acetylacetonate (11) or 7r-allylnickel bromide (1) activated by ethylaluminum sesquihalide or aluminum bromide (4). In a typical experiment, 11 in chlorobenzene was activated with excess ethylaluminum sesquichloride cyclooctene was then added at 0°C and the catalytic reaction followed by removing... 

Treatment of 19 with ethy(aluminum sesquichloride or aluminum bromide results in the formation of a new catalyst, which is active for the dimerization of olefins such as ethylene or propene but inactive for the dimerization of cyclooctene. 

The following conclusions can be drawn (a) ir-Allylnickel compounds are probably not involved in the catalytic dimerization of cyclooctene, because the highest reaction rate occurs when only traces of these compounds can be detected further, the concentration of the new 7r-allyl-nickel compound (19) becomes significant only after the catalytic reaction has ceased, (b) The complex formed between the original 7r-allylnickel compound (11) and the Lewis acid is transformed immediately upon addition of cyclooctene to the catalytically active nickel complex or complexes. In contrast to 7r-allylnickel compounds, this species decomposes to give metallic nickel on treatment of the catalyst solution with ammonia, (c) The transformation of the catalytically active nickel complex to the more stable 7r-allylnickel complex occurs parallel with the catalytic dimerization reaction. This process is obviously of importance in stabilizing the catalyst system in the absence of reactive olefins. In... 

The cyclooctene dimer [IrCl(C8H]4)2] can selectively hydrogenate cy-clooctene in mixtures with hex-l-ene, and an unsaturate route [Eq. 1(b)] via a monomeric olefin complex was demonstrated (181). The pentamethylcyclopentadienyl dimer was mentioned at the end of Section II, B, 2. 

Recently, Liew et al. reported the use of chitosan-stabilized Pt and Pd colloidal particles as catalysts for olefin hydrogenation [51]. The nanocatalysts with a diameter ca. 2 nm were produced from PdCl2 and K2PtCl4 upon reduction with sodium borohydride in the presence of chitosan, a commercial biopolymer, under various molar ratios. These colloids were used for the hydrogenation of oct-1-ene and cyclooctene in methanol at atmospheric pressure and 30 °C. The catalytic activities in term of turnover frequency (TOF mol. product mol. metal-1 h-1)... 

The cyclooctene complex was first isolated and adapted to cluster synthesis by Shapley and co-workers (156). The complex is formed by reaction of ethylene with H2Os3(CO)10 in cyclooctene, when only a trace of the vinyl adduct HOs3(CO)10-CH=CH2 is formed. The 13C-NMR spectrum indicates that substitution by the olefin of equatorial carbonyl groups on two different metal centers has occurred. The complex... 

A new class of heterogeneous catalyst has emerged from the incorporation of mono- and bimetallic nanocolloids in the mesopores of MCM-41 or via the entrapment of pro-prepared colloidal metal in sol-gel materials [170-172], Noble metal nanoparticles containing Mex-MCM-41 were synthesized using surfactant stabilized palladium, iridium, and rhodium nanoparticles in the synthesis gel. The materials were characterized by a number of physical methods, showed that the nanoparticles were present inside the pores of MCM-41. They were found to be active catalysts in the hydrogenation of cyclic olefins such as cyclohexene, cyclooctene, cyclododecene, and... 

The location of hydrogen atoms by electron diffraction suffers from some uncertainty, and in order to confirm the state of hybridization of the olefinic carbons, Traetteberg et al. (177) undertook a combined electron diffraction and strain energy calculation study of 1-methyl-frans-cyclooctene. Calculations, us-... 

Further important industrial applications of olefin metathesis include the synthesis of 3,3-dimethyl-l-butene ( neohexene , intermediate for the production of musk perfume) from ethene and 2,4,4-trimethyl-2-pentene, the manufacture of a,co-dienes from ethene and cycloalkenes (reversed RCM), and the ROMP of cyclooctene and norbomene to Vestenamer and Norsorex , respectively. 

This procedure illustrates a general method for preparing olefins by the elimination of an amine and a /3-hydrogen atom." The present method is more convenient for adaptation to large-scale laboratory preparation than is the Wittig modification, which utilizes liquid ammonia both methods give essentially the same overall yield of iraw5-cyclooctene. 

In a quest for a more environment-friendly process it has been found that reaction 8.4 can be catalyzed by Pd(II) complexes of various nitrogen-donor ligands (Scheme 8.1) under not too harsh conditions (100 °C, air) without the need of copper chlorides [10,11]. Of the investigated ligands, sulfonated batophenanthroline proved to be the best. Higher olefins, such as 1-hexene or cyclooctene were similarly transformed by this catalyst. Very importantly, there was no isomerization to internal olefins and 2-hexanone was formed with higher than 99 % selectivity. This outstanding selectivity is probably due to the absence of acid and Cu-chlorides. 

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