CHIROPTICAL SPECTRA AND MOLECULAR-GEOMETRY OF BICYCLIC DITHIOIMIDES

Several chiral bicyclic dithioimides were prepared by thionation of th e parent imides with Lawesson's reagent. Due to a flexibility of the d ithioimide chromophore, their CD spectra show significant solvent depe ndence. A substantial deviation of the chromophore from planarity was confirmed by the MNDO calculations and crystallographic structures of 4, 5b, 6 and 7. The observed CE sign corresponding to the lowest energ y n-pi transition can be predicted, upon careful examination of the m olecular geometry, by the antioctant rule with sector signs opposite t o those known for ketones. (C) 1998 Elsevier Science Ltd. All rights r eserved.