Azoles.: 42.: Nitropiperidinylimidazole derivatives

3-Chloro-1-(4-nitro-5-piperidinylimidazol-1-yl)propan-2-ol, C11H17ClN4O3, (3), is formed together with its unstable isomer 3-chloro-1-(5-nitro-4-piperidinylimidazol-1-yl)propan-2-ol, (2), by treatment of 3-chloro-1-(4,w5-dinilroimidazol-1-yl)propan-2-ol, C6H7ClN4O5, (1), With piperidine in a 1:2 ratio. In order to explain the position of the piperidine residue in the two isomeric products, (2) and (3), the X-ray investigation of the stable isomer, (3), was undertaken. It has two enantiomers, and in the centrosymmetric crystal lattice both enantiomers of (3) are present. In the asymmetric unit, four molecules of (3) are linked into two dimers, A/B [(S)-wenantiomers] and C/D [(R)-enantiomers], by two three-centre hydrogen bonds. The piperidine least-squares plane is nearly perpendicular to the planar imidazole system and the nitro group lies approximately in the plane of the imidazole ring. In (1), both nitro groups are rotated significantly from the imidazole plane and can be replaced by piperidine rings. The asymmetric unit contains only one molecule of (1). In the crystal lattice of (1), molecules are linked in chains by hydrogen bonds.