1,8,10,17-Tetraazapentacyclo[8.8.1.18,17.02,7.011,16]icosane X-ray crystal structure revisited

• The crystal structure of the icosane (1) has been determined by single crystal X-ray diffraction analysis.
• The reaction of formaldehyde with the cis and trans isomers of 1,2-cyclohexanediamine has been reinvestigated.
• The trans-isomer reacts to form the icosane (1), whereas the cis-isomer does not afford a crystalline product.
• The structure of 1 exhibits a twisted lawn chair conformation with both nitrogen atoms adopting the equatorial positions.
• The asymmetric unit is modeled as a 45:55 disorder between the R,R,R,R and S,S,S,S forms of the molecule.

The crystal structure of 1,8,10,17-tetraazapentacyclo[8.8.1.18,17.02,7.011,16]icosane (1) has been determined by single crystal X-ray diffraction analysis. The title compound crystallized in space group Fddd. The asymmetric unit is modeled as a 45:55 disorder between the R,R,R,R and S,S,S,S forms of the molecule. The structure exhibits a ‘twisted lawn chair’ conformation with both nitrogen atoms attached to the cyclohexane ring adopting the equatorial positions. In each molecule all chiral centers are of the same configuration; however both the R,R,R,R and S,S,S,S conformations are present in the unit cell and are related by a center of inversion. The crystal structure of 1 is compared with the structure of the tetraazadodecane (5).