title: Asymmetric transformation of N-nitrosamines by inclusion crystallization with optically active hosts.
abstract: Several N-nitrosopiperidines with chirality solely due to a hindered rotation about the N-N bond were resolved to enantiomers by inclusion crystallization with optically active diols (TADDOLs). The absolute configuration of the guest nitrosamines was deduced from the X-ray crystal structures of the inclusion complexes. The enclathrated nitrosamines were liberated by a competitive complexation of the host diols with piperazine. The optical activity of the resolved nitrosamines is manifested by their CD spectra. A simple chirality rule was proposed for a rationalization of the observed Cotton effect sign corresponding to the n-pi* electronic transition. The optically active nitrosamines are configurationally labile compounds and gradually racemize in solution but they are indefinitely stable in the solid state. The first-order kinetics of the racemization in solution allowed us to assign the N-N rotation barriers by simple polarimetric measurements.
authors: Department of Chemistry, Technical University, 80-952 Gdańsk, Poland.
authors: T
authors: T
authors: Olszewska
authors: M J
authors: MJ
authors: Milewska
authors: M
authors: M
authors: Gdaniec
authors: H
authors: H
authors: Małuszyńska
authors: T
authors: T
authors: Połoński
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D009602:Nitrosamines / Q000737:chemistry*; D013329:Structure-Activity Relationship
chemical_list: D009602:Nitrosamines