Olszewska T, Milewska MJ, Gdaniec M, Małuszyńska H, Połoński T. Asymmetric transformation of N-nitrosamines by inclusion crystallization with optically active hosts.
J Org Chem 2001;
66:501-6. [PMID:
11429821 DOI:
10.1021/jo001311v]
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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.
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