Structural and conformational study of diazabicyclanones and diazabicyclanols

3-Methyl-7-alkyl-3,7-diazabicyclo [3.3.1] nonan-9-ones and 9-ols have been studied by 1H, 13C NMF_IR and Raman spectroscopy and the crystal structure of 3,7-dimethyl-3,7-diazabicyclo[8.3.1] nonan-9-ol has been determined by X-ray diffraction. The ketones studied adopt in CDCl3 and (CD3)2SO solution a flattened chair-chair conformation; however, in the crystalline N-methyl N-benzyl derivative, the bicyclic system adopts a chair-boat conformation. X-ray data for 3,7-dimethyl-3,7-diazabicyclo [3.3.1] nonan-9-ol have revealed that the compound has crystallized in a chair-chair conformation stabilized by water and ethanol molecules. Frc.a IR data the existence of another chair anhydrous crystalline form stabilized by intramolecular hydrogen bonding has been deduced. The preferred conformation in solution of the diazabycyclanols mainly depends on the polarity of the solvent. © 1985.