Conformational study of N-substituted 8-azabicyclo[3.2.1]octan-3-ones

N-Substituted 8-azabicyclo[3.2.1]octan-3-ones have been studied by ¹H and ¹³C NMR spectroscopy. In CDCl₃ solutions, these ketones display the same preferred conformation. The pyrrolidine and piperidone rings adopt a flattened N-8 envelope and distorted chair conformation, puckered at N-8 and flattened at C-3, respectively, with the N-substituent in axial position with respect to the piperidone ring.