Chain cyclooctadiene

The synthetic route represents a classical ladder polymer synthesis a suitably substituted, open-chain precursor polymer is cyclized to a band structure in a polymer-analogous fashion. The first step here, formation of the polymeric, open-chain precursor structure, is AA-type coupling of a 2,5-dibromo-1,4-dibenzoyl-benzene derivative, by a Yamamoto-type aryl-aryl coupling. The reagent employed for dehalogenation, the nickel(0)/l,5-cyclooctadiene complex (Ni(COD)2), was used in stoichiometric amounts with co-reagents (2,2 -bipyridine and 1,5-cyclooctadiene), in dimethylacetamide or dimethylformamide as solvent. 

The reaction can be extended to other cycloalkenes such as cyclooctene, 1,5-cyclooctadiene, or 1,5-cyclooctadiene resulting in ozonides that have, in addition to the geminal 3-methyl-3-carbomethoxy substituents, a heptanal or cis-heptenal group at position 5 (in the case of 1,3-cyclooctadiene this side chain has the double bond in the non-conjugated position relative to the aldehydic group) <1993TL6591>. 

The polymerisation of monocyclic non-conjugated diolefins, which takes place by the double bond opening with simultaneous transannular migration, leads to cyclopolymers having bicyclic repeating units present in the main chain. A typical example of such cyclopolymerisation is the polymerisation of 1,5-cyclooctadiene [31,32] ... 

In Co- and Ni-mediated polymerizations of dienes the molar mass is commonly regulated by metal-free agents such as hydrogen, cyclooctadiene, 1,2-butadiene etc. In Nd-catalysis these additives do not result in a reduction of molar mass. What is the reason for this difference and are there metal-free chain modification agents which work with Nd-catalysts ... 

The reactivity of different dienes towards 4-(N,N-dimethylamino)phenyl cation (6) has been studied, and for open-chain dienes, such as 2,5-dimethyl-2,4-hexadiene, only the trans-pentadienylaniline is found in a 52% yield [30], In the case of cyclic dienes, transannular cyclization takes place, leading to an arylnortricyclene from norbornadiene and to l-arylbicyclo[3.3.0]octanes from 1,5-cyclooctadiene in moderate yields (Scheme 10.18) [30]. 

Ishii and coworkers developed a Mn(OAc)2-catalyzed hydrophosphonation of alkenes 40 (Fig. 47) [271]. The active Mn(III) catalyst is generated by reaction of Mn(OAc)2 with oxygen. Hydrogen abstraction from diethyl phosphite 169 forms a phosphonyl radical, which adds to 40. The resulting alkyl radical is reduced by 169 to continue the chain reaction. Alkylphosphonates 170 were isolated in 51-84% yield. With (3-pinene a cyclobutylcarbinyl radical ring opening was observed in 32% yield, while 1,5-cyclooctadiene underwent a tandem radical addition/ transannular 5-exo cyclization (cf. Fig. 38). 

Poly(l,4-butadiene) segments prepared by the ruthenium-mediated ROMP of 1,5-cyclooctadiene can be incorporated into the ABA-type block copolymers with styrene (B-106) and MMA (B-107).397 The synthetic method is based on the copper-catalyzed radical polymerizations of styrene and MMA from the telechelic poly(butadiene) obtained by a bifunctional chain-transfer agent such as bis(allyl chloride) or bis-(2-bromopropionate) during the ROMP process. A more direct route to similar block copolymers is based on the use of a ruthenium carbene complex with a C—Br bond such as Ru-13 as described above.67 The complex induced simultaneous or tandem block copolymerizations of MMA and 1,5-cyclooctadiene to give B-108, which can be hydrogenated into B-109, in one pot, catalyzed by the ruthenium residue from Ru-13. 

Via stereoselective ethenolysis of 1,5-cyclooctadiene (COD), Bykov et al. [25] prepared l,d5-5,9-decatriene, a precursor for the synthesis of many ds-isomeric insect sex pheromone compounds. In the presence of the MoCl5/Si02/Me4Sn catalyst system, at 20 °C and an ethene pressure of 25 bar, a 80 % conversion of COD was obtained with a selectivity of 68.4% for l,ds-5,9-decatriene. From this triene, many long-chain (CiQ-Cig) unsaturated acetates, alcohols and aldehydes can be obtained with the required biologically active cis conformation. Cross-metathesis of cyclooctene with a-olefins in the presence of the same catalyst gave... 

The first straight-chain A5,9 fatty acid to be synthesized was actually the (5Z,9Z)-5,9-hexacosadienoic acid [47]. The methodology developed by Djerassi et al. is shown in Fig. (17). This six-step synthesis started with the unusual controlled ozonolysis of one of the double bonds of (lZ,5Z)-l,5-cyclooctadiene to secure a 100% Z stereochemistry for what eventually was going to be the A9 double bond of the target molecule. Transformation of the product to the tosylated acetal, followed by Grignard coupling under dilithium tetrachlorocuprate catalysis afforded (Z)-4-heneicosenal, which after Wittig olefination with 4-carboxybutyltriphenylphosphonium bromide resulted in the desired A5,9... 

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