Of cyclooctadienes

Codimerization of butadiene with dicyclopentadiene (example 8, Table II) was shown to proceed via a crotyl-nickel complex (62). Ring contraction of cyclooctadiene (example 10, Table II) appears to be a hydride promoted reaction. The hydride-promoted dimerization of norbomadiene to -toly 1 norbornene (example 9, Table II) appears to be quite different from dimerization via a metallacycle (see Table I, example 16). 

Pawlow et al. (3) prepared multifiinctionalized high-trans-content elastomeric polymers using Grubbs second-generation ruthenium catalyst in the metathesis polymerization of cyclooctadiene, cyclopentene, and l,4-bis(trimethoxysilyl)-2-butene. 

An iridium catalyst (52) has been found to catalyse H-D exchange in a variety of unsaturated carboxylic acids, ketones and amines.155 The mechanism presumably involves displacement of cyclooctadiene by a solvent molecule, which later on is replaced by the a,p-unsaturated compound. 

It should be noted that a selective amidation can be achieved with 4-vinylcyclohexene, where only the terminal olefin reacts, and that in the case of cyclooctadiene a reaction across the ring also takes place (P). 

Cyclooctadienyl anion reacts spontaneously with 9-bromoanthracene and 1-bromon-aphthalene to yield aryl derivatives of cyclooctadienes. With PhBr or PhCl, photostimulation is necessary for the reaction to occur162. 

The ruthenium catalyst RuCl2(= CHPh)(PCy3)2 is able to promote both alkene metathesis polymerization (ROMP) and atom transfer polymerization (ATRP) [80,81]. The bifunctional catalyst A was designed to promote both ROMP of cyclooctadiene (COD) and ATRP of methyl methacrylate (MMA). Thus, catalyst A was employed to perform both polymerizations in one pot leading to diblock polybutadiene/polymethylmethacrylate copolymer (58-82% yield, PDI = 1.5). After polymerization the reaction vessel was exposed to hydrogen (150 psi, 65 °C, 8h), under conditions for Ru(H2)(H)Cl(PCy3)2 to be produced, and the hydrogenation of diblock copolymer could attain 95% [82] (Scheme 36). 

Replacement of cyclooctadiene in the zinc derivative 39 by butadiene leads to the trinuclear complex 40, which can be converted by reaction with lithium metal into 41 and metallic zinc. Under mild reaction conditions, 41 cannot be obtained directly from 34 and butadiene. 

These compounds have been obtained by the addition of cyclooctadiene to an equimolar mixture of /i3-allyl or /d -crotyl-(2,4-pentanedionato)palladiuni(II) and tetrafluoroboric acid in methylene chloride-ether solution.1 If silver tetrafluoroborate is on hand, the slight modification described below obviates the need to prepare the /3-diketonate complex as an intermediate. 

A different synthetic approach, namely, Na reduction of C0CI2 in the presence of cyclooctadiene (cod) in a THF/pyridine mixture (equation 39), gives a 16-electron complex (10) of identical composition, which is the conjugate analog of (9a), containing a jr-cyclooctenyl ligand. Compound (10) is considerably more stable towards heat and air than is (9). It has also been observed as a by-product when excess AIHR2 was employed in the synthesis of (9). 

Very recently, Grubbs and coworkers completed an analysis based on insight from mechanistic work on the relative rates of phosphine dissociation and olefin coordination (vide infra) in ruthenium alkylidene catalyzed olefin metathesis reactions. The study was based on numerous analogues of (4a), having different phosphine groups, for example, (4e), (4f), and (4g). Rates for ROMP of cyclooctadiene with the most potent of these new complexes were 340-fold greater than with (4a) (Scheme 1) ... 

Catalyst Ru-4 exhibits overall superior activity and improved substrate scope relative to catalyst Ru-2. For example, Ru-4 completes simple metathesis reactions, such as the RCM of diethyl diallylmalonate or the ROMP of cyclooctadiene, at rates several orders of magnitude greater than with Ru-2. In addition, whereas catalyst Ru-2 is unreactive toward sterically congested or electronically deactivated substrates, Ru-4 successfully mediates the formation of tetra-substituted olefins in five- and six-mem-bered rings systems [9], as well as CM to form tri-substituted olefins and products containing electron-withdrawing substituents [10]. 

Photodimerization of simple 1,3-dienes in a 4 1 + 4 r cycloaddition process is typically an inefficient process . This is not surprising, given the highly ordered transition state for [4+4]-cycloadditions, and the predominance of the unreactive s-trans conformation . As a result, as noted above [2 + 2]-cycloadducts are often the major product, accompanied by varying amounts of vinylcyclohexenes and cyclooctadienes. Crossed photocycloadditions employing 1,3-dienes with substituents at the 2- or 3-positions can furnish greater amounts of cyclooctadiene products (equation This presumably results from a perturbation of the diene conformational equilibration to provide a higher proportion of the s-cis conformer. 

Reagents (a) KOCN (b) RCOCl (c) hydrogenation in presence of cyclooctadiene-RhCl dimer and (+)-2,3-0-isopropylidene-2,3-dihydroxy-l,4-bis(diphenylphosphino)-butane or (+)-DIOP-Rh (cyclooctadienyl)chloride as catalysts (d), (i) P2S5, (ii) HQ. 

ABA triblock copolymers, where A was PBd and B either PS or PMMA were prepared by the combination of ROMP and ATRP techniques [122]. The PBd middle blocks were obtained through the ROMP of cyclooctadiene in the presence of l,4-chloro-2-butene or cis-2-butene-l,4-diol bis(2-bromo)propionate using a Ru complex as the catalyst. The end allyl chloride or 2-bromopropionyl ester groups were subsequently used for the ATRP of either styrene or MMA using CuX/bpy (X = Cl or Br) as the catalytic system (Scheme 50). Quantitative yields but rather broad molecular weight distributions (Mw/Mn higher than 1.4) were obtained. 

The first place in catalytic hydrogenation nowadays is taken by Rh or Ru complexes of BINAP. This ligand has axial chirality as the naphthalene rings cannot rotate past each other. These compounds were developed by Noyori, who with Knowles and Sharpless received the 2001 Nobel prize for their contributions to asymmetric synthesis. BINAP 20 is usually made from BINOL 19 and either 19 or 20 can be resolved. Rhodium complexes similar to those we have met include a molecule of cyclooctadiene and, as these are Rh(I) compounds, a counterion, often triflate 21. Both enantiomers of BINAP are available commercially.8... 

Potassium hydride is superior to phenylsodium, phcnylpotassium, or potassium for isomerization of cyclooctadienes to c/s-bicyclo[3.3.0]octene-2.1 Potassium... 

Another type of cyclooctadiene rearrangement is observed with a palladium complex 10> ... 

The hydrosiiyiation of butadiene with HSiMe3 catalyzed by nickel(O) complexes, such as Ni(PR3)2(CO)2, Ni(COD)2, Ni(CO)4, and Ni(CH2=CHCN)PPh3, gives a mixture of but-2-enyltrimethylsilane and octa-2,6-dienyltrimethylsilane together with a considerable amount of cyclooctadiene. Product ratio is affected by the donor ligand employed. ... 

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