Synthesis and physical properties of new 1,6-diazabicyclo[4.1.0]heptanes: Quantum-chemistry calculations and crystal structures simulations

Nine new 1,6-diazabicyclo[4.1.0]heptanes with alkyl substituents in position 7 were synthesized for the first time. The compounds were characterized by NMR and mass spectrometry, their densities were measured, and X-ray diffraction data were obtained for compounds 8, 12 and 13. The structure of conformers for 1,6-diazabicyclo[4.1.0]heptanes was studied using quantum chemistry methods. Crystal packings for 25 different compounds of the class 1,6-diazabicyclo[4.1.0]heptanes and 1,5-diazabicyclo[3.1.0]hexanes were modeled based on the Atom-Atom potential method. The enthalpies of formation and combustion of 1,6-diazabicyclo[4.1.0]heptanes and 1,5-diazabicyclo[3.1.0]hexanes are estimated and compared with their naphthenic analogs.