Aliphatic C–H/π and Heteroatom/π Interactions in N‐Aryl‐3,4‐(9′,10′‐dihydroanthracene‐9′,10′‐diyl)succinimides

Abstract

AbstractA series of N‐aryl‐3,4‐(9′,10′‐dihydroanthracene‐9′,10′‐diyl)succinimides have been synthesized as model compounds to study the interaction of an aromatic π system with aliphatic H atoms and heteroatoms such as oxygen, sulfur, and fluorine. The steric requirements of the rigid scaffold forces the N‐aryl residue and a benzene ring of the dihydroanthracenyl moiety to adopt an edge‐to‐face conformation in which one of the ortho‐substituents of the N‐aryl group interacts with the π system. The succinimides were generally obtained as mixtures of isomers and their ratios were considered as a function of the substitution pattern at the ortho positions of the N‐aryl residue. The experimentally observed ratios were in good agreement with those predicted computationally by DFT calculations at the BMK/cc‐pVDZ level of theory. From this study it was concluded that in these systems the aliphatic C–H/π interaction is mildly stabilizing and, to a certain extent, capable of overcoming unfavorable steric effects. On the other hand, the interaction of a π system with oxygen, sulfur, or fluorine atoms was destabilizing. When methyl or ethyl groups were allowed to compete with oxygen and fluorine for interaction with the benzene ring, C–H/π interactions were consistently observed to preferentially occur despite unfavorable steric effects.