Bicyclo octa-2,6-diene substituted

Ring-opening metathesis polymerization (ROMP) of substituted bicyclo octa-dienes or paracyclophane-enes initiated by Gmbbs molybdenum, tungsten-based carbenes have been used to prepare PPV s [178—181]. The living character of ROMP has been exploited to prepare soluble well-defined precursors, which can be converted into XI. Yu and Turner have used ROMP of tetra octyloxy-substituted paracyclo-phanedienes initiated by reactive ruthenium-based carbenes to prepare monodisperse, soluble yellow fluorescent PPV with an alternating cis-trans microstructure and molecular weights as calculated [178] (Fig. 9.21). 

Abbreviations acac, acetylacetonate Aik, alkyl AN, acetonitrile bpy, 2,2 -bipyridine Bu, butyl cod, 1,5- or 1,4-cyclooctadiene coe, cyclooctene cot, cyclooctatetraene Cp, cyclopentadienyl Cp, pentamethylcyclopenladienyl Cy, cyclohexyl dme, 1,2-dimethoxyethane dpe, bis(diphenyl-phosphino)ethane dppen, cis-l,2-bis(di[Atenylphosphino)ethylene dppm, bis(diphenylphosphino) methane dppp, l,3-bis(diphenylphosphino)propane eda,ethylenediamine Et,ethyl Hal,halide Hpz, pyrazole HPz, variously substituted pyrazoles Hpz, 3,5-dimethylpyrazole Me, methyl Mes, mesityl nbd, notboma-2,5-diene OBor, (lS)-endo-(-)-bomoxy Ph, phenyl phen, LlO-phenanthroline Pr, f opyl py, pyridine pz, pyrazolate Pz, variously substituted pyrazolates pz, 3,5-dimethylpyrazolate solv, solvent tfb, tetrafluorobenzo(5,6]bicyclo(2.2.2]octa-2,5,7-triene (tetrafluorobenzobanelene) THE, tetrahydrofuran tht, tetrahydrothicphene Tol, tolyl. 

As shown in Table 6 and Figure 1, the oxidation potentials of 2-substituted norbornadienes (1), 2-substituted bicyclo[2.2.2]octa-2,5-dienes (2) and 4-substituted [2.2]paracyclophanes (3) clearly indicate that the transannular interaction between two double bonds contributes already at the stage of the first electron transfer. Namely, in compounds 1-3, the electron is transferred from the unsaturated bond which is not substituted by the electron-withdrawing group, Figure 1 shows the... 

The thermolysis of the bicyclodiene 109 at 225 °C gives rise to equilibrium mixture of cyclooctatriene and its transformation products (see below)54. More recently the influence of a methoxy group on the thermal behavior of the bicyclo[5.1.0]octa-2,4-diene system was studied56. Heating of 8-ewdo-methoxydiene 115 in cyclooctane at 95 °C gaves rise to methoxy substituted diene 117 and not to the product 116 of butadienylcyclopropane rearrangement (equation 41). The thermolysis of the 8-exo-isomer 118 has taken place as an equilibrium reaction to give 6-ewdo-methoxy diene 119 (equation 42)56. These two reaction partners were separated by TLC. 

A series of substituted 1,3,5-cyclooctatrienes (e.g. VIII/150) has been synthesized according to Scheme VIII/28. They generally exist in equilibrium with their valence tautomers, bicyclo[4.2.0]octa-2,4-dienes. The equilibrium is largely effected by the nature and position of the substituents. They were isolated as the sole valence tautomers. This fact indicates the stabilization provided by the conjugation with the carbonyl group, is strong enough to maintain a 1,3,5-cyclooctatriene structure [84], Scheme VIII/28. 

A few cycloadducts of 7-substituted cycloheptatrienes have been converted to 4(8)-substituted homotropylidenes (bicyclo[5.1.0]octa-2,5-dienes)18,20. 

Thermal, or photochemical, decomposition of certain polycyclic diazines yields seven-membered rings. Thus, enr/o-10,ll-diazatetracyclo[4.3.2.0 .0 ]undec-10-ene rearranges to bicy-clo[5.2.0]nona-2,5-diene at 180°C (Section 2.4.1.5.2.8.). Substituted 9,10-diazatetracyclo-[3.3.2.0. 0 - ]dec-9-enes, e.g. 3, rearrange to give mixtures of bicyclo[5.1.0]octa-2,5-dienes and tetracyclo[3.3.0.0 . 0 ]octanes when photolyzed in methanol or benzene. ... 

Originally, the conversion of substituted bicyclo[2.2.2]octa-2,5-dienes into a precursor polymer of PPVs by ring opening metathesis polymerization (ROMP) has been shown by Grubbs using a molybdenum-based metathesis catalyst. The precursor polymer aromatizes in an inert atmosphere at 280 0, or in the presence of trioctylamine at 200°C. 

In a very early work, it was shown that substituted v6>-tricyclo[3.2.1.0 ]oct-6-ene derivatives give bicyclo[3.2.l]octa-2,5-dienes (Scheme 9.65)/ Biradical pathways were proposed. 

Cyclo-octa-2,4-dien-l-ol is converted into anti -2,3-epoxycyclo-oct-4-enol (91 %) on treatment with m-chloroperoxybenzoic acid, whereas t-butyl peroxide-VO(acac)2 gives the bicyclic ether (163 78 %). 2,6,6-Trimethylcyclohepta-2,4-dienol is converted into syn-2,3-epoxy-2,6,6-trimethylcyclohept-4-enol (65 %) by m-chloroperoxybenzoic acid and into (164 86%) by t-butyl per oxide-VO(acac)2- As the syn-epoxycyclo-heptenol gave (164) on treatment with VO(acac)2, it was suggested that in the t-butyl peroxide-VO(acac)2 epoxidations the bicyclic ethers were formed via the syn-2,3-epoxides and subsequent transannular S 2 substitution. The nature of the products obtained from reactions of epoxides with lithium diethylamide is solvent dependent. Thus the mono-epoxide of cyclo-octa-1,5-diene gives cyclo-oct-3-enone in benzene or ether and bicyclo[5,l,0]oct-2-en-syn-6-ol in HMPT the exocyclic... 

A useful compilation of 220 MHz n.m.r. data of substituted bicyclo[3,2,l]octan-6-ones has been published. The bicyclo[3,3,0]octyl cation appears to be implicated in the isomerization of bicyclo[3,2,l]oct-2-ene over SiOj-PaOj at 250 °C as deduced from the scrambling of label in [3- C]-tagged material and the distribution of label in the product, namely bicyclo[3,3,0]oct-2-ene. It has been found that 2,4-diphenyl-bicyclo[3,2,l]octa-2,6-diene (630) and its 6,7-dihydro-derivative undergo base-catalysed hydrogen-deuterium exchange at C-4 at essentially the same rate. Hence, the phenyl groups result in the total elimination of charge delocalization from C-4 to the C-6-C-7 double bond that is found in the unsubstituted bicyclo-octadiene. The... 

Other oxymercuration studies include those on the monoepoxide of cw,c/5-cyclo-octa-l, 5-diene, with neighbouring group participation of the oxiran oxygen, bicyclo[2,2,2]octene, cis- and rranj -cyclo-octenes and cyclononenes, 1,3-diphenylpropenones, and the bicyclic systems (492) and (493). The kinetics of methoxymercuration of substituted cinnamic acids and many aliphatic olefins have been measured. 

The addition of various carbon and heteroatom nucleophiles to (bicyclo[5.1.0]-octadienyl)iron cations has been reported. Mostly, the nucleophile attacks at the terminus of the dienyl system to form substituted (bicyclo[5.1.0]octa-2,4-diene)iron complexes. The nucleophile stereoselectively attacks from the rear side of the dienyl system, opposite to the iron atom. The method can be used for the synthesis of cis-2-(2 -carboxycyclopropyl)glycine (CCG-III) (Scheme 4-180). ... 

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