Cyclooctadiene derivatives

The cyclohexadiene derivative 130 was obtained by the co-cyclization of DMAD with strained alkenes such as norbornene catalyzed by 75[63], However, the linear 2 1 adduct 131 of an alkene and DMAD was obtained selectively using bis(maleic anhydride)(norbornene)palladium (124)[64] as a cat-alyst[65], A similar reaction of allyl alcohol with DMAD is catalyzed by the catalyst 123 to give the linear adducts 132 and 133[66], Reaction of a vinyl ether with DMAD gives the cyclopentene derivatives 134 and 135 as 2 I adducts, and a cyclooctadiene derivative, although the selectivity is not high[67]. 

The dimerization of isoprene has been accompHshed by methods other than heating. Thus isoprene has been dimerized by uv radiation in the presence of photosensitizers to give a complex mixture of cyclobutane, cyclohexene, and cyclooctadiene derivatives (36,37). Sulfuric acid reportedly... 

Concerning the transformation of [4]radialenes, the parent compound (2) has been studied best, despite its high instability in solution at room temperature or in the solid state (see above). We have already mentioned that 2 can be kept indefinitely at — 78 C, but undergoes dimerization and polymerization in solution at 20 C. The dimerization leads to cyclooctadiene derivative 113. Trimethylenecyclobutane behaves analogously, and 5,5,6,6-tetraphenyl[4]radialene 66 reacts in the same manner to give 114 at 60 °C in chloroform solution (equation 6). Since thermal (4 + 4) cycloadditions should not occur in a concerted manner, it has been suggested that this reaction is a stepwise process in which the reacting 1,2-dimethylenecyclobutene unit exhibits 1,4-diradical character. ... 

The reaction is sensitive to steric hinderance. Aromatic ketones are reduced to hydrocarbons. Unsaturated ketones are fully reduced and with no selectivity. Complexes of the type Ir(Chel)(CH2=CH2)2Cl, with Chel = 2,2 -bipyridine or phenantholine derivatives, behave as catalyst precursors for hydrogen transfer from isopropanol to ketones and Schiff bases. Potassium hydroxide is required as cocatalyst to convert the isopropanol coordinated to the Ir(I) ion, in the neutral isopropoxy derivative. Enolates that are present would act as inhibitors when coordinated to the cationic derivative. Ethylene complexes are better precursors than the corresponding cyclooctadiene derivatives, because they are activated more easily and more completely, and they show high catalytic activity. The most active complexes is the 3,4,7,8-Me4 phen derivative, which, at 83°C, gives turnovers of up to 2850 cycles/min. Reduction of 4-r-butylcyclohexanone affords 97% of the tra/u-alcohol. 

Tricarbonyl( 7 f/ -l, 5-cyclooctadiene)iron, prepared by photolysis, rearranges on heating to the rj -1,3-cyclooctadiene derivative. 

This would certainly work if we could prepare enantiomerically pure pre-kingianin A (i.e., 2a or 2b). Although there are a few examples of asymmetric induction in the preparation of similar cyclooctadiene derivatives, these have been tested with a more substituted tetraene precursor, which yields almost exclusively the two endo diastereomeric products. The best of these gives only moderate diastereomeric excesses, and it does require a bit of work. " Furthermore, none of these methods has been applied to the preparation of cyclooctadienes that are oidy monosubstituted at the tetraene termini. 

A ruthenium complex with a cyclooctadiene derived n -alkenyl... 

Palladium-catalyzed cycloisomerization providing the thermodynamically less-favored exo-alkylidene compounds has been elusive. However, lately this unique selectivity has also been accessed by utilizing N-heterocyclic carbene and 1,5-cyclooctadiene-derived catalysts [65]. 

CuOTf-catalyzed photocycloaddition of the tetraene 96 produces a mixture of the compounds 98,99, and 100 (Scheme 25). The 1,2-divinyl cyclobutanes 97 initially formed from [2 + 2]-addition of the tetraene 96 undergo further reaction on prolonged irradiation in the presence of CuOTf to form these products. The tricyclic compound 100 arises from intramolecular 2jt + 2Jt addition of cyclooctadiene derivative 99. In fact, the transformation of cis,c/s-l,5-cyclooctadiene 101 to the tricychc compound 102 on irradiation in the presence of CuCl was the first example of an intramolecular Cu(I)-catalyzed photocycloaddition reaction. ... 

Several authors developed the method further of Ni(0)-mediated couplings to generate several PPP derivatives (9, 13, 14. They described homocouplings of various 1,4-dihalobcnzene derivatives by means of nickel(lI)chloridc/triphenylpho-sphine/zinc or the niekel(0)/cyclooctadiene complex. 

A derivative of cyclopentyne has been trapped in a matrix. Although cycloheptyne and cyclohexyne have not been isolated at room temperatures, Pt(0) complexes of these compounds have been prepared and are stable." The smallest cyclic allene" so far isolated is l-/err-butyl-l,2-cyclooctadiene 107." The parent 1,2-cyclooctadiene has not been isolated. It has been shown to exist transiently, but rapidly dimerizes." " The presence of the rert-butyl group apparently prevents this. The transient existence of 1,2-cycloheptadiene has also been shown," and both 1,2-cyclooctadiene and 1,2-cycloheptadiene have been isolated in platinum complexes." 1,2-Cyclohexadiene has been trapped at low temperatures, and its structure has been proved by spectral smdies." Cyclic allenes in general are less strained than their acetylenic isomers." The cyclic cumulene 1,2,3-cyclononatriene has also been synthesized and is reasonably stable in solution at room temperature in the absence of air." ... 

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. 

In 2004, Dieguez et al. reported the development of novel C2-symmetric dithioether ligands derived from the corresponding binaphthyl or biphenanthryl diols. Thus, various (i )-binaphthyl dithiols substituted by alkyl groups on the sulfur atom in order to increase the steric bulk were synthesised, and the corresponding mononuclear cationic Ir(I) -cyclooctadiene complexes were prepared and characterised (Scheme 8.20). NMR studies demonstrated that, in all cases, the coordination of the ligands proceeded with complete stereoselectivity at the... 

Based upon the above-mentioned assumptions, the reaction scheme in Figure 3.1 is reduced to the scheme shown in Figure 3.2A. It should be noted that active catalyst is used in the reaction scheme in Figure 3.1 while most asymmetric hydrogenation processes use a pre-catalyst (11). Hence, the relationship between the precatalyst and active catalyst needs to be established for the kinetic model. The precatalyst used in this study is [Et-Rh(DuPhos)(COD)]BF4 where COD is cyclooctadiene. The active catalyst (Xq) in Figure 3.2A is formed by removal of COD via hydrogenation, which is irreversible. We assume that the precatalyst is completely converted to the active catalyst Xq before the start of catalytic reaction. Hence, the kinetic model derived here does not include the formation of the active catalyst from precatalyst. 

The reactions can be made enantioselective by using enantiomerically pure IpcBH2 for hydroboration of alkenes and then transforming the products to enantiomerically pure derivatives of 9-BBN by reaction with 1,5-cyclooctadiene.22... 

Thus the range of bicyclic peroxides available via peroxymercuration may be quite limited. Nevertheless where the method works best, namely with 1,5- and 1,4-cyclo-octadiene, it makes a valuable contribution in that each peroxymercuration is regiospecific and leads to a dioxabicyclodecane that is isomeric with the [4.2.2] compound 23 available via photooxygenation (Eq. 18). Furthermore, the [3.3.2] compounds derived from 1,5-cyclooctadiene are, to the best of our knowledge, the only bicyclic peroxides obtained to date that do not contain either a 5- or a 6-membered dioxacycloalkane ring. 

Electrophylic halogenation of 9-oxabicyclo[3.3.l]nona-2,6-diene (139), a heteroanalog of 39, in the presence of water and its epoxidation with performic acid results in ring closure to 4,8-disubstituted 2,6-dioxaada-mantane derivatives.168 4,8-Dibromo-2,6-dioxaadamantane is also prepared from the syn-dibromide of 1,5-cyclooctadiene.169... 

The thermolysis of ladderanes has been studied in detail (Scheme 1). On heating, bicyclo[2.2.0]hexane and its derivatives exhibit skeletal inversion and cleavage to 1,5-hexadiene derivatives.26 The thermolysis of anti- and yyft-tricyclo[4.2.0.02,5]octanes and their derivatives gives cis,cis- and cis, trans-1,5-cyclooctadienes, cis- and trans-1,2-divinylcy clobutanes, and 4-vinylcyclohexene as ring-opening products.27-29 Furthermore, syn-tricyclo-[4.2.0.02,5]octane isomerizes to aw//-tricyclo[4.2.0.02,5]octane.29c,d The thermodynamic parameters and the reaction mechanisms for these thermal reactions have been discussed. 

The nickel-catalyzed [4 + 4]-cycloaddition of butadiene to form cyclooctadiene was first reported by Reed in 1954.90 Pioneering mechanistic and synthetic studies largely derived from the Wilke group advanced this process to an industrially important route to cyclodimers, trimers, and other molecules of interest.91-94,943 95,96 While successful with simple dienes, this process is not useful thus far with substitutionally complex dienes as needed in complex molecule synthesis. In 1986, Wender and Ihle reported the first intramolecular nickel-catalyzed [4 + 4]-reaction of... 

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