Cyclooctene derivatives

Both o- and p- substituted bis(methylthio)arylmethylium salts, derived by the 5-methylation of substituted dithiobenzoates, dimerise following deprotonation to give 1,4-dithianes. Only with the former isomer is the quinone methide generated leading to a cyclooctene derivative <96LA1159>. 

Fig. 3.31 Steric control in alternating ROMP Tendencies of norbomene and cyclooctene to give productive olefin metathesis upon coordination are illustrated by a thick arrow (preferred monomer) or a thin arrow (less favoured monomer) (a) only minor steric hindrance SlMes greatly favours the polymerisation of the strained norbomene (b) the rotating phenylethyl-group induces a steiically more congested active site, leading to preferred incorporation of the smaller cyclooctene (c) the flexible and small cyclooctene derived polymer fragment permits the incorporation of the bulky norbomene...

The unusually stable cross-ozonide 89 has been reported <06TA1780>, and a range of isomeric mono- and disulfoxides of the E-cyclooctene-derived 1,2,3-trithiolane 90 have been prepared <06T5441>. 

The opening move was the transformation of the known glucopyranoside 355 into exomethylene vinylpyranose 356. TIBAL-promoted Claisen rearrangement of 356 provided the cyclooctene derivative 357 almost quantitatively, which was then transformed to protected cyclooctanose 358 by methylation followed by hydroboration-oxidation. Installation of the hydroxymethyl function at C5 required three further operations oxidation of the Cs-hydroxyl, Tebbe methylenation, and hydroboration-oxidation. In the event, a mixture of epimeric... 

In ROMP cyclic olefins are polymerized to polyalkenamers. Both 1 and 3 can be used for this reaction, but catalyst 3 was found to be significantly more efficient for the polymerization of cyclooctene derivatives (Eq. 13) [30]. Polymerization commences with initiation of the catalyst through dissociation of a neutral ligand such as a tricyclohexylphosphine for 1 and 3 (see... 

In contrast, the intramolecular energy transfer in cyclooctene derivatives 63E-65E, which are tethered to benzoate, isophthalate, and terephthalate moieties through a (/ ,/ )-2,4-pentadiol linker, does not appear to be seriously affected by the steric bulk of 1-alkylation (Scheme 10) [50]. Upon irradiation at — 65°C, 63, 64, and 65 afforded ZJE ratios of 0.8,0.15, and 0.06, with diastereomeric excesses (des) of 33, 37, and 44%, respectively. 

Liu, K.T., Lesca, P. Pharmacological properties of Dibenzo (a,c) cyclooctene derivatives isolated from fructiis Schizandra chinensis III. Inhibitory effects on carbon tetrachloride-induced lipid peroxidation, metabolism and covalent binding of carbon tetrachloride to Hpids. Chem. Biol. Interact. 1982 41 39-47... 

It was mentioned earlier that the overall distortion of a C=C double bond is in most cases a combination of more than one type of deformation. Comparison of 24a with 24b (Table 3) reveals that introduction of an ethyl group in both adamantylidene moieties leads to twist as well as symmetrical oop bending. Also, the contribution of oop bending to the overall deformation of the double bond in the trans-cyclooctene derivative 37b should be mentioned here. 

The 1,4-elimination of 193, given in the Eqs. 52 and 53, represents two pathways leading to two different iminium ions 194 and 195, whose relative distribution will depend on whether the reaction is performed under thermodynamic or kinetic control. The species 194 is a cyclooctene derivative and the species 195 a cyclohexane derivative. The cyclohexane derivative 195 must, of course, predominate in a thermodynamically controlled reaction. Like the species 193, the species 196 also represents two pathways for 1,4-elimination as shown in Eqs. 54 and 55. Fortunately, both the pathways yield the same product 197. The reactions shown in Eqs. 56 and 57 are examples of elimination resulting from the 1,3-diol mono-tosylate system. An electron pair orbital on the hydroxylic oxygen that is antiperiplanar to the cleaving central ac c bond provides the necessary electronic push in which the former makes the latter weak, and therefore labile for cleavage. The reaction shown in Eq. 57 was used by Corey and coworkers in a synthesis of... 

Methylene transfer to the cyclooctene derivative 4 proceeds with complete diastcrcofacial selectivity. Thus, the less hindered face of the olefin is attacked by the diiodomethane/diethyl-zinc reagent exclusively27. 

Other Unsaturated Compounds. - The dienals 13 (with D-xylo-, D-lyxo- and D-arahino-configurations) have been condensed with the phosphonate 14 to give the enone adducts 15 the intramolecular Diels-Alder reactions of these adducts are mentioned in Chapter 22. Treatment of the unsaturated lactone 16 with the Tebbe reagent has afforded 17 its conversion into a cyclooctene derivative is covered in Chapter 18. Exposure of the cyclic sulfate 18 to base has afforded a mixture of the exo- and endo-olefins 19 and 20, ° and a syn-selective dihydroxyla-tion of the 3,4-unsaturated pyranoside 21 generated predominantly the D-allo product. Synthesis of the branched-chain 5,6-ene 22 using standard methods, and its conversion into a cyclitol during the first total synthesis of (—)-tetracyc-line is mentioned in Chapter 22. 

There have been several reports of the use of ring-closing metathesis applied to sugar-derived compounds for the preparation of cycloheptene and cyclooctene derivatives. The mannose-derived dienes 42 (R = H, Ac) were converted in high yields to the carbocycles 43 using Grubbs ruthenium-based catalyst, and the... 

In Figure 7 the conversion versus time for the polymerisation of the epoxide functionalised cyclooctene derivatives is depicted. Remarkable enough, the yield for the epoxides is very low. A possible reason for this behaviour can be the eventuality that the epoxide function inhibits coordination of the substrate to the metal centre. 

Figure 7. Conversion versus time for the polymerisation of the epoxide functionalised cyclooctene derivatives...

Percy and co-workers applied a similar strategy in the synthesis of a trisubstituted cyclooctene derivative in an effort to determine the limits of relay ring-closing metathesis.Reaction of diene 315 (R = H) in the presence of 4 (three additions 10 mol %, then 5 mol % then 5 mol % over a 12-day period) and Ti(Oi-Pr)4 in refluxing dichloromethane furnished the corresponding octocycle 316 in only 24% yield. However, when a relay approach was employed, diene 317 (R = (CH2)3CHCH3) gave the... 

Porco and co-workers used a diversity oriented/ring-closing metathesis approach to construct several complex systems as small molecule protein modulators.Microwave irradiation of Michael adduct 323 in the presence of a catalytic amount of 4 in refluxing dichloromethane gave the corresponding cyclooctene derivative 324 in modest yield. The authors included several additional examples as part of their report. 

After publishing the facile synthesis of tran -cyclooctene derivatives from the readily accessible cfr-cyclooctene (Royzen et al., 2008), Fox and colleagues extended this work to develop a fast bioconjugation strategy based upon the IVED-DA cycloadditions (Blackman et al., 2008). Maleimide functional frans-cyclooctene was coupled to thioredoxin (after reduction to produce the solvent exposed cysteine) via standard Michael addition chemistry. The now trans-cyclooctene functional thioredoxin (Trx-ene) could then be further modified extremely efficientiy with an electron-deficient tetrazine (3,6-di-(2-pyidyl)-i-tetrazine) shown in the left side of Figure 2.15. The overall strategy is depicted in Scheme 2.5. 

Osaka University 16.5 Asymmetric Photoisomerization of Cycloalkenes Cyclooctene Cyclooctene Derivatives Cyclohexene and. . 16-12... 

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