Stereochemistry and chiroptical spectra of 3-azabicyclo[3.1.0]hexan-2-ones and thiones

Article abstract of DOI:10.1016/S0957-4166(97)00111-0

Several optically active substituted 3-azabicyclo[3.1.0]hexan-2-ones and their thiocarbonyl analogues have been synthesized, and their circular dichroism spectra studied. The crystal structure of thiolactam la showed that the bicyclic skeleton of the title compounds assumes a sofa-like geometry. It is postulated that the cyclopropyl moiety and amide or thioamide group constitute an inherently chiral chromophore, helicity of which determines the Cotton effect sign corresponding to the n-π* electronic transition. The weak π-π* Cotton effect of thiolactams shows opposite sign to that observed for the lowest energy excitation.