Cyclopentacorannulene

The recently determined X-ray crystal structure of cyclopentacorannulene 25 provides an additional opportunity to test the performance of theory in predicting the minimum energy structures of nonplanar conjugated systems. Table 4 presents the C-C bond lengths in the crystal and a comparison with ab initio values calculated at HF/3-21G and HF/6-3IG levels. The agreement between experimental and theoretical bond lengths is very satisfactory with root mean square devia-... 

Table 4, Comparison of Experimental Bond Lengths with the Ab Initio Results for Cyclopentacorannulene 25...

Cyclopentacorannulene (67) was obtained as a mixture with corannulene (in ratio 7 3) in 10-15% yield from dichloride 66 by flash vacuum pyrolysis at 1,000 °C (Scheme 18) [106]. In contrast, 67 could also be prepared, in 20% yield, by titanium-mediated carbenoid couplings of 68 in solution phase [34]. 

Acecorannulene (69) was generated in excellent yield from cyclopentacorannulene (67) by nickel-catalyzed hydrogenation (Scheme 19) [106]. Alternatively, 69 was also synthesized in the solution phase from dibromide 34 by either Pd-catalyzed Stille-type coupling [62] or by treatment with phenyllithium [57]. 

Sygula, A., 8c Rabideau, P. W. (1999). Non-pyrolytic syntheses of buckybowls Corannulene, cyclopentacorannulene, and a semibuckmin-sterfullerene. Journal of the American Chemical Society, 121, 7800-7803. 

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