Cyclooctatetraene route

Cyclooctatetraene was first synthesized in 1911 by a route that involved the following transformation ... 

With dichlorosilylene, similar products result along with smaller amounts of the 2-silaindane. These are thought to result from insertion, or addition, of the silylene to the bicyclo valence isomer (11) of cyclooctatetraene (Scheme 24) (75ZOB2221), although a similar route to that in Scheme 23 is also possible. 

Access to homotropenylium ions can be achieved by two general routes. The first involves the addition of an electrophile to a cyclooctatetraene or cyclooctatetraene derivative, an approach which can be considered to correspond to a homoallyl route (Scheme 4). In this route the electrophile is generally attached stereoselectively to the endo position on C(8)18 7,1 74. The second approach involves the ionization of a bicyclo[5.1.0]octadienyl derivative. This is the cyclopropylcarbinyl approach (Scheme 4). This route has the potential of generating a wide range of differently substituted cations however, the starting materials can be difficult to access75 . 

The intermolecular ortho photocycloaddition of acetylenes to benzene has provided routes to cyclooctatetraenes [78-84], Intramolecular photocycloaddition of alkynes to aromatic rings is also investigated. Morrison et al. reported that photolysis of 6-phenyl-2-hexyne in hexane solution using 254-nm light leads to the formation of bicyclo[6.3.0]undecatetraene (251 and/or 252) [284] (Scheme 70). Pirrung prepared various bicyclo[6.3.0]undecatetraenes (254a-e) by the in-... 

The head-to-head dimerization with formation of a butatriene derivative was scarcely observed as the main catalytic route (Scheme 15, catalytic cycle B). Nevertheless, this was the case from benzylacetylene in the presence of RuH3Cp (PCy3) as a catalyst precursor in tetrahydrofuran at 80 °C, which gave more than 95% of (Z)-l,4-dibenzylbutatriene [54], and from ferf-butylacety-lene with two efficient catalytic systems capable of generating zero-valent ruthenium species, RuH2(PPh3)3(CO) and Ru(cod)(cyclooctatetraene) in the presence of an excess of triisopropylphosphine, which led to (Z)- 1,4-di- tert-butylbutatriene as the major compound [57-59]. 

Simple cyclooctatetraenediyls [M(C8H8)] (M = Eu, Yb) can be made by reaction of cyclooctatetraenewith solutions ofthe metal in liquid ammonia. Another route to [M(CsH8)] (Sm, Yb) is the reaction of the metals with cyclooctatetraene using iodine as catalyst. These compounds are not monomers, but the Lewis base adduct [M(C8H8)(py)3] has a piano-stool structure. 

The third route involves metathesis polymerization of cyclooctatetraene with tungsten catalysts, yielding polyacetylene as an insoluble film along with oligomers (iOi). By first polymerizing cyclooctene and then adding cyclooctatetraene, a soluble, red block copolymer was obtained. On the basis of the visible absorption spectrum, at least two or three cyclooctatetraene units were concluded to have been added to the polymer chain forming a short polyacetylene block. No conductivity data were reported for this copolymer. 

In principle, conjugated materials may either be directly synthesized via metathesis polymerization of acetylene or 1-alkynes, via ROMP of various cyclooctatetraenes (COTs) or via ROMP of polyene precursors as realized in the Durham route [107-111]. The first direct polymerization of acetylene to yield black untreatable unsubstituted polyacetylene was achieved with W(N-2,6-i-Pr2-C6H3)(CH-t-Bu)(OC-t-Bu)2 [112]. In order to obtain soluble polymers, polyenes were prepared via the ROMP of a polyene-precursor, 7,8-bis(trifluoromethyl)tricyclo[4.2.2.02 5]deca-3,7,9-triene (TCDTF6), using initiators such as W(N-2,6-i-Pr2-C6H3)(CH-t-Bu)(OC-t-Bu)2) (Scheme 5.10) [113, 114]. 

Another route to mono-cyclooctAtetraene compounds is cleavage of one ring from the bis-COT complexes by protonation. Kablitz and Wilke have prepared (C0T)ZrCl2 and its THF adduct in this manner (20). 

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