Cyclooctatetraene, synthesis

Table 4.12 Summary of reaction metrics and synthesis tree parameters for cyclooctatetraene synthesis plans ranked according to overall kernel (maximum) RME .

Reppe s cyclooctatetraene synthesis also appears to be ir complex concerted (41). The formation of Binor-S of (XI), and of CaHg thus may be formally related, tt complex, multicenter processes. Accordingly, the reaction of acetylene with Zn[Co(CO)4]2 produced small amounts of cyclooctatetraene (52). This is the first reported case in which cyclooctatetraene was formed using a catalyst containing metals other than nickel, and on a binuclear catalyst center. 

Gorman, C.B., Ginsburg, E.J., Grubbs, R.H., 1993. Soluble, highly conjugated derivatives of polyacetylene from the ring-opening metathesis polymerization of monosubstituted cyclooctatetraenes synthesis and the relationship between polymer structure and physical properties. I. Am. Chem. Soc. 115, 1397-1409. 

J. W. Copenhaver, M. H. Bigelow, Acetylene and Carbon Monoxide Chemistry (New York, 1949) p 246 W. Reppe, Acetylene Chemistry, U.S. Dept. Commerce PB 18852-S (1949) Neue Entwicklungen auf dem Gebiet des Acetylens und Kohlenoxyds (Berlin 1949) H. Kroper, Houben-Weyl 4/II, 413-422 (1955) D. W. F. Hardie, Acetylene, Manufacture and Uses (New York, 1965) p 67 L. F. Fieser, M. Fieser, Reagents for Organic Synthesis (New York, 1967) pp 61, 183, 185, 190, 519, 720, 722, 723. Review of carbonylations A. Mullen, Carbonylations Catalyzed by Metal Carbonyls-Reppe Reactions in New Syntheses with Carbon Monoxide, J. Falbe, Ed. (Springer-Verlag, Berlin, 1980) pp 243-308. Mechanistic study of cyclooctatetraene synthesis R. E. 

Triphenylphosphine stabilizes the nickel atom by forming a complex. As it blocks at least one of the coordination positions on the nickel atom, only three acetylene molecules may add to it, thus making the formation of cyclooctatetraene impossible (79). Complexes of nickel with 1,1-dicyano-and 1,1,2-tricyanoethylene behave similarly, yielding approximately stoichiometric quantities of benzene and cyclooctatetraene CgHg, but affording exclusively benzene in the presence of triphenylphosphine 51, 82). The original catalysts for Reppe s (2, 83) cyclooctatetraene synthesis were all... 

Scheme 8.40 Cyclooctatetraene synthesis through Nickel(0)-catalyzed [2-I-2-I-2-I-2] cycloadditions of diynes.

Scheme 8.41 Cyclooctatetraene synthesis throngh Pd-catalyzed homocoupling of horylvinyl iodohenzenes.

The reactions of the palladium-cyclobutadiene complexes with excess alkyne produced persubstituted cyclooctatetraenes in analogy to Reppe s catalytic cyclooctatetraene synthesis (Pollock and Maitlis, 1966 Reppe and Schweckendiek, 1948). Although the cyclobutadiene ligand can be transferred between metals [Eq. (76)] (Maitlis, 1971b), liberation of the ligand... 

Nickel plays a role in the Reppe polymeriza tion of acetylene where nickel salts act as catalysts to form cyclooctatetraene (62) the reduction of nickel haUdes by sodium cyclopentadienide to form nickelocene [1271 -28-9] (63) the synthesis of cyclododecatrienenickel [39330-67-1] (64) and formation from elemental nickel powder and other reagents of nickel(0) complexes that serve as catalysts for oligomerization and hydrocyanation reactions (65). 

How might you use the Hofmann elimination to accomplish this reaction How would you finish the synthesis by converting cyclooctatriene into cyclooctatetraene ... 

Semi bull valcncs are well-known intermediates in the synthesis of cyclooctatetraenes, 1,5-diazo-cines and 1,3,5,7-tetrazocines. There are also some examples for the synthesis of azocines, although so far only for W-substituted lactam derivatives, e.g. 1.25,26... 

Figure 4.37 Synthesis trees for Reppe synthesis of cyclooctatetraene (a) treating each molecule of acetylene as a separate input (b) treating all 4 acetylene molecules as a single input.

Cope, A.C. Overberger, C.G. (1948) CycUc Polyolefins. I. Synthesis of Cyclooctatetraene from Pseudopelletierine. Journal of the American Chemical Society, 70, 1433-1437. 

Synthetic applications of other decarbonylation reactions are found in the conversion of cyclooctatetraene to barrelene 250), with the photodecarbonyla-tion of a Diels-Alder adduct as key step (2.31) and the preparation of tetrathioesters from 1,3-dithioles (2.32) 251). The most remarcable application of such a reaction up to date is the synthesis of tetra t.butyltetrahedrane from a tricyclic ketone precursor (2.33) 252). 

Additions of benzene, not to olefins but to acetylenes have been utilized in the synthesis of cyclooctatetraenes (4.38)443). 

If the cycloaddition and cycloreversion steps occurred under the same conditions, an equilibrium would establish and a mixture of reactant and product olefins be obtained, which is a severe limitation to its synthetic use. In many cases, however, the two steps can very well be separated, with the cycloreversion under totally different conditions often showing pronounced regioselectivity, e.g. for thermodynamic reasons (product vs. reactant stability), and this type of olefin metathesis has been successfully applied to organic synthesis. In fact, this aspect of the synthetic application of four-membered ring compounds has recently aroused considerable attention, as it leads the way to their transformation into other useful intermediates. For example aza[18]annulene (371) could be synthesized utilizing a sequence of [2 + 2] cycloaddition and cycloreversion. (369), one of the dimers obtained from cyclooctatetraene upon heating to 100 °C, was transformed by carbethoxycarbene addition to two tetracyclic carboxylates, which subsequently lead to the isomeric azides (368) and (370). Upon direct photolysis of these, (371) was obtained in 25 and 28% yield, respectively 127). Aza[14]annulene could be synthesized in a similar fashion I28). 

Ogliaruso et al. (1966) formed the ten 7r-electron monohomocycloocta-tetraene dianion [148]. In the same way that cyclooctatetraene dianion can be formed by donation of two electrons to cyclooctatetraene, their synthesis was the two-electron donation to the monomethylene adduct. H NMR studies support the assignment of the homoaromatic form [148] and exclude the classical form [149]. 

The synthesis of bis(rj8-cyclooctatetraene)uranium(IV) (uranocene)J from uranium tetrachloride and (cyclooctatetraene)dipotassium was first published in 1968.1 The method reported here is a modification of that procedure and is suitable for a large variety of cyclooctatefraene complexes.2-4 BisO 8-cyclo-octatetraene)uranium(IV) has also been prepared by the reaction of uranium tetrafluoride with (cyclooctatetraene)magnesium in the absence of solvent.5 Direct reaction of finely divided uranium metal with cyclooctatetraene vapors at 150° also gives some uranocene.5 However, both methods give low yields. 

Bis(r78-cyclooctatetraene)uranium(IV) and its precursor, dipotassium cyclo-octatrienediide, are air and water sensitive. A knowledge of inert-atmosphere techniques is essential to conduct this synthesis successfully.7 ( Caution. Dry dipotassium cyclooctatrienediide may react explosively with air therefore it always should be handled under an inert atmosphere or in vacuum.)... 

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