Dehydrobenzo annulene

Zojer et al.192 have discussed the limitations of the essential-state model in calculating the TPA of bis(dioxaborine-)-substituted chromophores. Lukes and Breza193 have made an AM1-ZINDO/SOS study of spirobifluorene type molecules. Jha et al.194 have employed their method of obtaining model exact solutions in the PPP approximation to calculate TPA cross-sections for trans-stilbene and 7,8-disubstituted stilbenes. Zhou et al 95 and Liu et al.196 have studied one and two photon absorption in octupolar compounds using DFT and ZINDO/SOS methods and the group has applied similar methods to trigonal dehydrobenzo[l8]annulenes.197... 

Access to the [1,2-6]IF core was also discovered through collapse of the dehydrobenzo[12]annulene scaffold. First described by Eglinton and coworkers in 1960 (Scheme 6), tetrayne 24 underwent a double transannular cyclization when reacted with elemental Na in liquid ammonia to provide octahydroindeno[l,2-(7] fluorene 25 as a mixture of two isomers in 69% yield [41]. Further treatment with 15% Pd/C aromatized the central ring to afford 6,12-dihydroindeno[l,2-/7] fluorene (26). 

Scheme 9.2 Cyclotrimerization of the cuprous salt of o-iodophenylacetylene 2 in pyridine to give the antiaromatic dehydrobenzo[l 2]annulene 1 [8].

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