Cubyl

The repeated occurrence of the otherwise rare catemer VII in the family of cubanecarboxylic acids under study here is quite likely the result of fortification of the catemer by the C-H—O hydrogen bond formed by the acidic cubyl C-H group.1261 This... 

The acidity of the unadivated cubyl-H is comparable to NH3 (pKa 38). Cubyl H-atoms are at least 105-106 times more acidic than vinyl and phenyl hydrogens (K. A. Lukin, J. Li, P. E. Eaton, N. Kanomata, J. Hain, E. Pun-zalan, R. Gilardi, Synthesis and chemistry of 1,35,7-tetranitrocubane induding measurement of its acidity, formation of o-nitro anions, and the first preparations of pentanitrocubane and hexanitrocubane , J. Am Chem. Soc, 1997,119, 9591-9602 and the references cited therein). 

Next, the attention was turned to addition of azido groups to carbon-carbon double bonds of side-chains attached to the cubyl ring system. In this approach, cubane derivatives with unsaturated side-chains and added azido groups to these side-chains were synthesized using the reaction ... 

Two more extensively conjugated cubyl derivatives were synthesized as shown in Fig. 2.9. 

Moriarty, R. M., J. S. Khosrowshahi, R. S. Miller, J. Elippen-Andersen, and R. Gi-lardi. 1989. Eree-radical arylation of cubane using cubyl lead acylates. J. American Chemical Society 111 8943-44. 

Dodecahedryl dication 242 Diamantane-4,9-diyl dication 243 3,3 -(l,l -Biadamantyl) dication 243 Cubyl-l,4-dicarboxonium ion 244... 

Applications of Electronic Structure Calculations to Explaining and Predicting the Chemistry of Three Reactive Intermediates—Phenylnitrene, Cubyl Cation,... 

Section 4 discusses the apphcation of electronic structure calculations to understanding and predicting the outcome of experiments on three different types of Rl. The examples in this section are taken from research, performed in collaborations between the author s group and the groups of experimentalists. The three RIs discussed in Section 4 are phenyinitrene, cubyl cation, and propane-1,3-diyls. 

APPLICATIONS OF ELECTRONIC STRUCTURE CALCULATIONS TO EXPLAINING AND PREDICTING THE CHEMISTRY OF THREE REACTIVE INTERMEDIATES—PHENYLNITRENE, CUBYL CATION, AND PROPANE-1,3-DIYL... 

Figure 22.5. The MP2/6-31G bond lengths and net Mulliken charges (in italics) at C—H groups, computed for cubyl cation 4. Resonance structures A and B are consistent with the calculated bond lengths and charges whereas, structure C is not.

For many polycyclic carbocations there is a good correlation between the changes in strain energies on carbocation formation, predicted by molecular mechanics calculations, and the solvolysis rates. However, at 70° cubyl cation is formed 10 times faster than expected from this correlation." " " What is responsible for this huge rate acceleration ... 

The results of our calculations on cubyl carbocation 4, which showed that stabilization of 4 comes from interactions between the ipso carbon and the (3 carbons (as represented by resonance structures A and B in Fig. 22.5), suggested that stabilization of diradical 5 comes from the same types of interactions. These too can be represented by resonance stmctures, two of which are shown in Figure 22.6. Delocalization of electrons from all six of the bonds between the a and (3 carbons in 5 requires that the in-phase combination of nonbonding AOs be left empty, and that is why the pair of nonbonding electrons preferentially occupies the out-of-phase combination of nonbonding AOs at Cl and C4. 

Why Are the Cubyl Hydrogens of Methylcubane More Reactive than the Methyl Hydrogens Toward Abstraction by tert-Butoxyl Radicals The experimental puzzle, which our calculations on 4 helped to solve, was posed by Della s finding that terf-butoxyl radicals preferentially abstract hydrogens from the carbons of the cube in methylcubane (6), rather than from the methyl... 

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