Conformational Analysis and Study of Hydrogen Bonding of Iodobicycloheptanyl-N '-(trifluoromethanesulfonyl) Acetimidamides

摘要

Structure of iodobicycloheptanyl-N'-(trifluoromethanesulfonyl) acetimidamide epimers and its selfassociates in crystal, solution and gas phase was studied by X-ray diffraction, IR spectroscopy and quantum chemistry methods. In an isolated molecule, the 2S,7R-enantiomer is energetically preferred, the structure of which is also realized in the crystal. According to X-ray diffraction analysis, in the crystal, (2S,7R)-N(7-iodobicyclo2.2.1heptan-2-yl)-N'-(trifluoromethanesulfonyl) acetimidamide molecules are linked by intermolecular hydrogen bonds R-NH center dot center dot center dot O=S. However, according to the quantum-chemical calculations data, the Tf-NH center dot center dot center dot O=S type H-bonds turn out to be stronger by 3 kcal/mol when dimers are formed. The relative energy of formation of (2S,7S)-N-7-iodobicyclo2.2.1heptan-2-yl)-N'-(trifluoromethanesulfonyl) acetimidamide self-associates is similar to 10 kcal/mol.