1.4- disubstituted cubanes

Another type of rearrangement was observed with silver and palladium(II) salts [2]. Treatment of 1,4-disubstituted cubanes with AgClO at room temperature gave 2 isomers among the 10 possible isomers of the cuneane product (Scheme 3.2). Catalytic activity of Pd(II) for the rearrangement was similar to that of Ag(I). 

The skeleta of other strained systems such as cubanes and related compounds can also be reorganized in the presence of silver salts. Rearrangements of cubanes were described in the early 1970s. Eaton et al.35 showed that mono- or disubstituted cubanes gave a mixture of polycyclic regioisomers (Scheme 3.21). No yields were given. 

Figure 9. New pathway for fluxional interconversions of substituted icosahedra via tetracapped cuneane and tetracapped cubane intermediates (or transition states). This proposed scrambling process, which maximizes connectivity and obeys electron-counting rules, is illustrated for the interconversion of a 1,2-disubstituted ort/io-icosahedron into a 1,7-disubstituted meta-icosahedron.

Rg. 29. A comparison of some of the shortest and longest cubane cage distances, both of which occur at disubstituted cube edges. 

Irradiation of iodocubane (35) afforded the methyl ether 37 accompanied by a small amount of the reduction product cubane (36). The high ratio of ionic to radical product indicates that the cubyl cation is easier to form than the 1-norbomyl cation, in agreement with solvolysis data and ah initio calculations showing stabilization of cubyl cation by cross-ring bonding to the P carbon atoms. The 1,4-diiodide 38 afforded the mono- and disubstituted derivatives 39 and 40 in CH3OH and wet CH5CN. 

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