Cyclo-l,5-octadiene

The coordination chemistry of 2-(2-pyridyl)phosphole ligands toward Pd(II) centers was investigated with the aim of gaining insights into their coordination behavior. Thus, the reaction of 3b-d with [(cod)PdMeCl] (cod = l,5-cyclo-l,5-octadiene) afforded the corresponding air-stable complexes 6b-d as single diastereoisomers in excellent yields (Scheme 12.3) [15]. 

Ac = Acetyl acac = Acetylacetonate bda = Benzylidene-acetone BINOL = l,l -bi-2-naphthol Bn = Benzyl brsm = Yield based on recovered starting material Bu = Bntyl CAN = Ceric anunonium nitrate CBS = Corey/Bakshi/Shibata catalyst [(+) or (—)-(S)-2-methyl-oxazaborolidine] COD = Cyclo-l,5-octadiene COT = Cyclooctatetraene Cp = Cyclopentadienyl Cp = Penta-methylcyclopentadienyl Cy = Cyclohexyl DCC = Dicy-clohexylcarbodiimde DMF = Ai,A-dimethylformainide DMPU = l,3-dunethyl-3,4,5,6-tetrahydro-2(lH)-pyrimidin-one DMSO = Dimethylsnlfoxide dppe = Diphenylphosp-hinoethane dr = Diastereomer ratio dppm = Diphenylphos-phinomethane E = Electrophile ee = Enantiomeric excess EHMO = Extended htickel molecular orbital Et =... 

Catalyst 1, [(z7 -crotyl)(cycloocta-l,5-diene)nickel]hexafluorophosphate ( naked nickel ), was prepared following a procedure developed for the methallyl isomer by Tkatchenko and coworkers [35, 37]. Thus bis(cyclo-l,5-octadiene)nickel was reacted with crotyl bromide to yield the bromide-bridged (// -crotyl)nickel dimer. Abstraction of the bromide by thallium hexafluorophosphate in the presence of cyclo-1,5-octadiene yielded 1. The structure of 1 in solution is consistent with its solid state X-ray crystal structure [38]. 

Catalyst 2, [(// -crotyl)(cyclo-l,5-octadiene)palladium]hexafluorophosphate ( naked palladium . Fig. 4.4), was prepared similarly to that of its nickel analog. First the chloride-bridged dimer, [(// -crotyl)Pd( z-Cl)]2, was synthesized, followed by addition... 

The cationic complex, [Ni(Ci2Hi9)]SbF6 can be made independently from Ni(cyclo-l,5-octadiene)2, butadiene, and HSbFg. This material exhibited similarly high activity toward norbornene polymerization. 

The polymerization of ether and thioether monomers was also studied, and it was found that the rate of polymerization was a great deal slower with the functionalized monomers. The number of methylene units between the olefin and the heteroatom greatly affected the rates observed, giving credence to the chelation effect shown in Fig. 6.1. In addition, catalyst 2 polymerizes 1,5-hexadiene, whereas catalyst 6 mainly cyclizes the metathesis dimer to cyclo-l,5-octadiene. At this point there is no clear explanation for this result, and, furthermore, the reason that the COD generated did not undergo ROMP in these reactions is unclear. The data from these experiments clearly shows that Lewis basic functionality retards the rate of metathesis with complex 6 more than with complex 2, although 6 is clearly the more functional group-tolerant complex overall [35]. 

Among the cyclodienes, the reaction of cyclo-l,5-octadiene (258) with (C2Hb)2A1H has been studied in detail (255). With 2 moles of diethylalane and 1 mole of diene a bis-hydroalumination product is first formed. This, on prolonged heating and subsequent hydrolysis, gives the bicyclic pentalane in high yield ... 

On the other hand, treatment of norbornadiene with a catalytic amount of Ru(cod)(cot) (cod = cyclo-l,5-octadiene, cot = cyclooctatetraene) and an electron-deficient olefin caused a unique dimerization reaction to afford cage compound 18 (Scheme 7.6) [8]. Although the precise reaction mechanism is unclear, it is proposed that the reaction proceeds through the alkylruthenium intermediate 13. It adds intramolecularly to the alkene moiety to form 14, which further adds to the remaining alkene moiety. Subsequent oxidative addition of a C-C bond located in proximity to the ruthenium center affords 15. Reductive elimination ensues to give the alkylruthenium intermediate 16. Subsequent P-carbon elimination breaks the strained norbornane skeleton to furnish alkylruthenium 17. P-Hydride elimination produces the cage molecule 18 along with a ruthenium hydride species. 

The relatively easy rearrangement of cis-l,2-divinylcyclobutane was first reported by Vogel (1958) who found that at 120° ci5,cis-l,5-cyclo-octadiene was the only product. 

More recently, kinetic data have become available for the isomerization of this compound and also for the iraws-l,2-divinylcyclobutane (Hammond and DeBoer, 1964). From determinations of the rate of formation of the cia-cis-l,5-cyclo-octadiene from the cis-l,2-divinylcyclobutane at four temperatures between 65 and 108° C, an enthalpy of activation of... 

RuCmH,2, Ruthenium(II), (V-cycloocta-1,5-diene)bis(V"2-propenyl)-, 26 254 RuC1FbNjPC,4H2i, Ruthenium(II), tris-(acetonitrile)chloro(V-l,5-cyclo-octadiene)-... 

As a result, the (ri6-l,3,5-cyclo-octatriene)(ri2-l,5-cyclo-octadiene)ruthenium is formed with yields of 93 and 35% with and without US treatment, respectively. Among other 7i-complexes synthesized in a US field, the Fe(CO)2(C5Me5)(C2H5) 834 was isolated as a result of the two-step process (3.289) [748,749] ... 

Photoisomerization of (Z)-l-methylcyclo-octene 59aZ sensitized by chiral benzene(poly)carboxylates suffers significantly from steric effects. The photosensitization of 59aZ with bulky sensitizers leads to photostationary E/Z ratios and product ee s much lower than those obtained for less-hindered (Z)-cyclo-octene 38Z [158]. Enantiodifferentiating photoisomeri-zations of (Z,Z)-l,3-cyclo-octadiene and (Z,Z)-l,5-cyclo-octadiene (71Z and 78Z) have also been studied by using chiral benzene(poly)carboxylates at various temperatures [159]. Photosensitization of 71Z with hexa-(—)-menthyl benzenehexacarboxylate affords the (E,Z)-product 71E in 18% ee in pentane at —40 °C. In the photoisomerization of 78Z in pentane sensitized by (—)-menthyl benzoate, the (—j- Zj-isomer 78E is only slightly favored giving a 2% ee [126]. 

Dowbenko (1964) has shown that carbon tetrachloride, chloroform and several other compounds react with a s-cis-l,5-cyclo-octadiene by a free-radical transannular 1,5-cyclo-addition to give derivatives of bicyclo-[3,3,0]octane. He suggested that the cyclo-addition may occur by a concerted reaction in which the configuration of the diene is such that the two double bonds lie in close proximity, or alternatively by a step-wise reaction which involves a free-radical addition across the ring. 

Either triphenylarsonium benzoylylide or dibenzoylylide form complexes with bis(l,5-cyclo-octadiene)nickel these oligomerise ethylene under mild conditions . The dibenzoyl derivative is the more effective catalyst of the two, this being ascribed to the greater stabilization provided by the second benzoyl group the monobenzoyl derivative provides largely linear alkenes, but the dibenzoyl derivative leads to decreased linearity in the products. 

F4BIr02P2C]tH]t, Iridium(III), diaquadihy-dridobis(triphenylphosphine)-, tetra-fluoroborate( 1 - ), 26 124 F4BIr02P2C42H44, Iridium(III), bis(ace-tone)dihydridobis(triphenylphos-phine)-, tetrafluoroborate(l -), 26 123 F4BIrP2C35H3i Iridium(l + ), (T) -l,5-cyclo-octadiene)[ 1,3-propanediylbis-(diphenylphosphine)]-, tetrafluorobor-ate(l-), 27 23... 

Photolytic rearrangement. Irradiation of the w-complex of s cyclo-octadiene with cuprous chloride produces tricyclo[3.3.0.02- ]octane, a remarkably stable hydrocarbon. ... 

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