Synthesis and properties of 2,3-dihydro-1H-corannuleno[2,3-cd]pyridine (=2,3-dihydro-1H-dibenzo[1,10:6,7]fluorantheno[3,4-cd]pyridine) derivatives: Heterocyclic peri-anellated corannulenes

Abstract

The anellation of a 6-membered ring to the 2,3-position of corannulene (= dibenzo[ghi, mno]fluoranthene; 1) leads to curved aromatic compounds with a significantly higher bowl-inversion barrier than corannulene (see Fig. 1). If the bridge is -CH2-NR-CH2-, a variety of linkers can be introduced at the N(2) atom, and the corresponding curved aromatics act as versatile building blocks for larger structures (see Scheme). The locked bowl, in combination with an amide bond (see 9 and 10), gives rise to corannulene derivatives with chiral ground-state conformations, which possess the ability to adapt to their chiral environment by shifting their enantiomer equilibrium slightly in favor of one enantiomeric conformer. Rim annulation of corannulene seems to display a significantly lower electron-withdrawing effect than facial anellation on [5,6]fullerene-C60-I(h), as determined by an investigation of the basicity at the N-atom of CH2-NR-CH2 (see 4 vs. 15 in Fig. 2).