Azahomocubanes – A New Paper in RSC Advances

Cubane (C₈H₈) and homocubane (C₉H₁₀) are very strained molecules. Substitution of a carbon atom for a nitrogen one to reduce the tension in homocubane has been elusive until recently (Fahrenhorst-Jones et al. 2022). In contrast to cubane, substitution of C by N can occur at four different positions, so the obvious question is which one would be the most stable.

Geometry optimizations at the M06-2X-D3/def2-TZVP level of theory and energy refinement on those structures at the CCSD(T)/aug-cc-pVTZ level were carried out to assess their electronic structures. Their Gibbs free energy differences (kcal/mol) are shown below.

The strain energy was calculated through hypohomodesmotic reactions, and they were all around 110 kcal/mol, which is lower than that of azacubanes (~117 kcal/mol) or even cubane (~160 kcal/mol). V_S,min calculations were employed to assess the basicity of compounds 1-4, however since the obtained values lie outside the applicability domain of our reported models in JCIM, we weren't able to provide a pK_b value but rather a qualitative hint to their protonation affinities.

This research in collaboration with Prof. Gabriel Merino and María Fernandez from CINVESTAV and is available at RSC Advances DOI:10.1039/d3ra05117j an open access publication of the Royal Society of Chemistry.