Cubane halogenation

In these compounds, an alternative structure to the cubane cluster is found, for example in [Ph3PAgI]4.106 This is the chair or step type of arrangement, illustrated in Figure 2, in which two of the four halogen atoms retain a coordination number of three. This arrangement has also been found in some copper(I) halide complexes with bis(diphenylphosphino)methane.1O7 10S The pyramidal coordination of the halogen atom is similar to that in the cubane structure, although often more distorted. 

Non-activated methyl groups are never attacked in these reactions toluene can be functionalized but isolation of the resulting benzyl halides from these PTC mixtures is difficult. Most remarkable is that strained hydrocarbons such as cubane (5) or 2,4-didehydroadamantane (6) can also be halogenated with conservation of the cage [27], in marked contrast with the halogenation reactions of these substrates with halogen radicals [40]. Dihalogenations with either the same or a differ-... 

Another class8 are those with monatomic ligands (CuXL)4 where L is usually R3P or py and X is usually a halogen but can be SR. These have two main limiting structures, each of which may be distorted. The first is the cubane structure (17-H-III) in which there is a Cu4 tetrahedron with a triply bridging halide on each face and a ligand on each 4-coordinate Cu atom. Many of these compounds are luminescent.9... 

Ethylzinc chloride and ethylzinc bromide are tetrameric in benzene solutions and are believed to have the cubane-type structure shown in Figure 27. In the Z114X4 core, the zinc-halogen coordination is relatively weak consequently when these compounds dissolve in coordinating solvents or when... 

An alternative putative route to 62 is from 63, an adduct of cubene with the poorer Diels-Alder diene 1,3-butadiene. In 62, the proximity of the double bond to the two hydrogens which mnst be removed for formation of two new CC bonds may enable, possibly with the aid of a transition metal reagent, closure of the cyclobutene cap onto the cubane moiety to give [3,4]prismane. One could imagine halogenating... 

Triethyltelluronium halides, [Et3TeX]4 are tetrameric cubane supermolecules, 216, held together by secondary bonds (Te - Cl 3.448 A, Te- -I 3.813-3.861 A) between tellurium and halogen in addition to the electrostatic attraction. Triphe-nyltelluronium iodide, PhsTel forms dimers associated into two-dimensional sheets (514, 515]. The chloride PhjTeCl is a dimer (Te- -Cl 3.142-3.234 A) [516]. 

At this point, it is interesting to compare the absence of reactivity of a-halocyclopentanones under Favorskii rearrangement conditions, with the ring contraction observed when such a-halocyclopentanones are included in cage structures used as precursors of cubane derivatives. We will show in what follows that this marked difference in reactivity can be explained by the equatorial stereochemistry of the halogen in the cage a-cyclentanone derivatives. 

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