Bicyclo deca- 1,3,5,7,9-pentaene

Azulenes derived from the parent hydrocarbon bicyclo[5,3,0]deca-pentaene or azulene (IX) also involve charged structures having a negatively charged cyclopentadienide ring, as in (X). They are considered in more detail in Chapter Vlll. 

Another structure with a 10-7r-electron conjugated system is bicyclo[6.2.0]deca-1,3,5,7,9-pentaene. The crystal structure of the 9,10-diphenyl derivative (Fig. 9.6) shows the conjugated system to be nearly planar. " ... 

Bicyclo[6.2.0]deca-2,4,6,8,10-pentaene has been synthesized, and a number of molecular orbital and molecular mechanics calculations have been performed to determine whether it is aromatic or antiaromatic. Consider the structure and discuss the following points. 

An interesting aspect in the context of this section, however, is the question whether a carbene can add to the C(9) = C(10) bond of naphthalene and if in the product atoms C(9) and C(10) are connected to each other by a single bond in a cyclopropane derivative ( bisnorcaradiene ) (8.16), or whether there is no longer a bond between them, i.e., l,6-methano[10]annulene (8.17 bicyclo[4.4.1]un-deca-l,3,5,7,9-pentaene) is formed, or if an equilibrium between these two valence isomers can be detected. 

Tricyclo[6.2.0.0 ]deca-1 A7.9-tetraene to Bicyclo[6.2.0]-deca-1A5A9-pentaene... 

Tricyclo[6.2.0.0 °]deca-l,4,7,9-tetraene gives bicyclo[6.2.0]deca-l,3,5,7,9-pentaene in a first-order process at 100°C (Scheme 11.7). ... 

Structure of TMEDA complex of lithium bicyclo[3.2.1]octa-2,6-dienide Crystal structure of 9,10-diphenylbicyclo[6.2.0]deca-l,3,5,7,9-pentaene Hiickel molecular orbitals for phenalene... 

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