Stereochemistry of 1,2,3,4,5,6,7,8-Octakis(Dichloromethyl)Anthracene

1,2,3,4,5,6,7,8-Octakis(dichloromethyl)anthracene (1) has been obtained by photochlorination of 1,2,3,4,5,6,7,8-octamethylanthracene. Signals in the ¹H NMR spectrum of 1 have been assigned by isotopic labeling and 2D NMR exchange spectroscopy. The relative steric energies of 20 selected conformations of 1 have been estimated by empirical force field calculations. The same calculations indicate that the spatial separation of the two sets of four dichloromethyl groups on the terminal rings of the anthracene skeleton renders the sets moderately independent. Homo- and heterodirectional relationships between subcycles of the molecular model are discussed. An analysis of the proton signal count and of the NOE involving the aromatic and peri dichloromethyl methine protons indicates that the ground-state structure of 1 has an all-geared homodirectional conformation. A topomerization barrier of 22.2 kcal mol^-1 has been determined for 1 by the spin saturation transfer method.