Influence of the CH/B replacement on the reactivity of boranthrene and related compounds

The influence of the replacement of CH groups by boron atoms on the reactivity of planar polycyclic aromatic hydrocarbons has been explored by means of computational tools. To this end, [4 + 2]-cycloaddition reactions involving anthracene and neutral boranthrene with different dienophiles such as ethylene, acetylene, and CO2 have been compared. In addition, the influence of additional fused aromatic rings (pentacene or borapentacene) on the reactivity of these species has been also explored. It was found that the B-doped systems are systematically much more reactive than their all-carbon counterparts from both kinetic and thermodynamic points of view. The observed trends in reactivity are quantitatively analyzed in detail using state-of-the-art methods, namely, the activation strain model of reactivity and the energy decomposition analysis method. Our calculations reveal the importance of molecular orbital interactions as the key factor responsible for the enhanced reactivity of the B-doped systems.