Dodecahedranes—

Spherical, pentagonal dodecahedrane is the thermodynamically most stable CjoHjo-polycycloalkane. It is the so-called CjjHjo stabilomer . It should therefore be available by thermod5mamically controlled, e.g. acid-catalyzed, isomerization of less stable C24H20-isomers. Experiments along this line, e.g. treatment of the basketene photo-dimer with Lewis... 

A different kind of dehydrogenation was used in the final step of Paquette s synthesis of dodecahedrane. ... 

Molecules such as P4 and the polyanionic clusters such as Si4- or As2- that are discussed in Section 13.2 are representatives of electron precise closo clusters. Organic cage molecules like tetrahedrane (C4R4), prismane (C6H6), cubane (C8H8), and dodecahedrane (C20H20) also belong to this kind of cluster. 

If no y-H atom is available, or if for sterie reasons abstraction of a 6-H atom is facilitated, this latter reaction occurs with formation of a cyclopentanol. A series of such sequences has been used in the synthesis of dodecahedrane 409a,b>. 

The availability of cyclopentenones from butanolides allows the lactone annulation to facilitate the synthesis of cyclopentyl natural and unnatural products. An example that highlights the latter is dodecahedrane (178) for which 179 constitutes a critical synthetic intermediate 136,137). Lateral fusion of cyclopentenones as present in 179 can arise by acid induced reorganization and dehydration of 180. While a variety of routes can be envisioned to convert a ketone such as 182 into 180, none worked satisfactorily137 On the other hand, the cyclobutanone spiro-annulation approach via 181 proceeds in 64 % overall yield. Thus, the total carbon cource of dodecahedrane derives from two building blocks — cyclopentadiene and the cyclopropyl sulfonium ylide. 

Strategies based on known, highly elaborated, but nevertheless readily accesible, starting materials with a "complexity index" as near as possible to the "complexity index" of the target molecule. This strategy has also been applied to non-natural compounds as, for instance, in the synthesis of triquinacene by Woodward [37] and in the syntheses of dodecahedrane by Paquette (Domino Diels-Alder adduct) [38] and Prinzbach ("pagodane") and their associates [39]. 

The product diacid has served as starting material for the synthesis of tetracycio[7.2.1.0 . 0 ]dodeca-2,7-diene-5,12-dione, C g-hexa-quinacene, (Cj)-Ci7-heptaquinane derivatives, the parent dodecahedrane mol ecu e, and a number of substituted dodecahedranes. ... 

Dodecahedryl dication, (123), was generated from the dodecahedryl monocation (122), which was in turn obtained by ionizing dodecahedrane, hydroxydodeca-hedrane, or chlorododecahedrane (121) in SbF5/S02ClF at The... 

In a third approach substituents were removed from a preformed dodecahedrane cage. In this way the synthesis of [20-fJfullerene was possible in the gas phase [154]. However, extensions of this approach to syntheses of fullerenes consisting of 60 or more C-atoms are conceptually very difEcult. 

---