Polycyclic aromatic hydrocarbons (PAHs) in which five-membered rings have been interspersed among the six-membered rings generally display curved systems that can be either fully closed (fullerenes) or partially open (bowl-shaped fullerene fragments), depending on the number of five-membered rings. Both classes of compounds belong to the larger family we call 'GEODESIC POLYARENES.' Herein, we highlight the utility of high temperature aryl radical cyclizations as a general strategy for constructing strained geodesic polyarenes. We also report the first examples of reactions at the 'interior' carbon atoms of neutral PAHs that are not fullerenes, e.g. carbene additions, 1,3-dipolar cycloadditions, osmylation, nucleophilic addition of MeLi, and electrophilic addition of CHCl 2 and CCl 3 .

Circumtrindene (1), a C 36 H 12 geodesic polyarene that represents 60% of fullerene-C 60 , forms cationcomplexes with both silver ion (1 Á Ag þ ) and tetramethylammonium ion [(Me) 4 N þ Á 1] in chloroform solution at room temperature (K a > 20 M À1 for both cations). Preferential binding in the concave pocket of 1 is predicted by DFT calculations for both cations; however, this stereochemical assignment has not yet been confirmed experimentally.

SummaryCircumtrindene (6, C36H12), one of the largest open geodesic polyarenes ever reported, exhibits fullerene-like reactivity at its interior carbon atoms, whereas its edge carbons react like those of planar polycyclic aromatic hydrocarbons (PAHs). The Bingel–Hirsch and Prato reactions – two traditional methods for fullerene functionalization – afford derivatives of circumtrindene with one of the interior 6:6 C=C bonds modified. On the other hand, functionalization on the rim of circumtrindene can be achieved by normal electrophilic aromatic substitution, the most common reaction of planar PAHs. This peripheral functionalization has been used to extend the π-system of the polyarene by subsequent coupling reactions and to probe the magnetic environment of the concave/convex space around the hydrocarbon bowl. For both classes of functionalization, computational results are reported to complement the experimental observations.

Fragments of Fullerenes: Novel Syntheses and Properties -[about 17 refs.]. -(SCOTT, LAWRENCE T.; BRONSTEIN, HINDY E.; PREDA, DORIN V.; ANSEMS, RONALD B. M.; BRATCHER, MATTHEW S.; HA-GEN, STEFAN; Atual. Fis.-Quim.

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