Tricyclic cycloheptadienes

When the double bond of the enyne possesses a cyclopropyl substituent, an intramolecular [5+2] cycloaddition of alkyne and vinylcyclopropane takes place [75, 76]. The ruthenacycle does not undergo /l-hydride elimination but a rearrangement of the cyclopropane to produce a ruthenacyclooctadiene. Thus, a variety of bicyclic and tricyclic cycloheptadienes were obtained in good yields [75] (Eq. 55). 

The intramolecular reaction of the carbene from diazo ester 280, which contains a 1,3-diene moiety in the ester group and a double bond adjacent to the carbene center, leads to the formation of a substituted 1,2-divinyl-cyclopropane, whose CIS isomer then undergoes a Cope rearrangement to give substituted cycloheptadiene. In such a way, bicyclic 281 and tricyclic 282 y-lactones with a neighboring seven-membered carbocycle have been obtained (89JOC930). 

One example of an acid-catalyzed divinylcyclopropane to cycloheptadiene rearrangement which has been documented is the formation of tricyclic compound 3. ... 

Carbene addition to dienes, employing alkenyl-substituted diazoacetates (vide supra), has also been performed in an intramolecular fashion28,29. After in situ Cope rearrangement, bicyclic and tricyclic fused cycloheptadiene derivatives are generated as single diastereomers. 

An interesting expansion of this methodology uses reactions of Fischer carbenes with dienynes to produce bicyclic and tricyclic cycloheptadienes, through cw-divinylcyclopropane intermediates. In the intermolecular version, a molybdenum alkylalkoxycarbene reacts with a substituted dienyne to produce the cfs-divinylcyclopropane intermediate which, under the reaction conditions, undergoes a [3,3]-sigmatropic rearrangement to produce a mixture of bicyclo[5.3.0]decanes [Eq. (31)] [71]. The electron-withdrawing nature of the carbethoxy... 

Stereo- and regiospecific cyclisation of [(Ti4-diene)Fe(CO)3] complexes such as (34) afforded225 a high yield route to tricyclic ammonium complexes such as (35). It was reported226 that tricarbonyliron derivatives of 6-hydroxy-2,4-cyclohexadien-l-one, derived from the tricarbonyliron(tropone) precursor were easily oxidised to give [tricarbonyliron(2,4-cycloheptadiene-1,6-dione)]. 

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