NMR spectroscopic and theoretical studies on the isomerism of 1,5-benzodiazepin-2-one derivatives containing a perfluorinated side chain.

The isomerism of 1,5-benzodiazepin-2-ones 3 containing a perfluorinated side chain was investigated by 1H-, 13C-, 15N- and 19F NMR spectroscopy in different solvents. Compounds 3 exist in CDCl 3 , (D 6)acetone, CD 3 CN and (D 5)pyridine solution as one species, whereas in (D 6)DMSO and (D 7)DMF partial (E / Z) isomerisation about the exocyclic C2=C3 bond occurs resulting in two isomers. Gibbs free energies (ΔG) and Free activation energies (ΔG≠) were calculated based on BP86 and BP86-SCRF DFT computations. Image 1 • Fluorine containing 1,5-Benzodiazepin-2-ones exist in solution as one isomeric form due to an intramolecular hydrogen bond. • In solvents that are both polar and basic a second isomer appears to a certain amount. • The new isomer is formed by breaking off the hydrogen bond and (E / Z) isomerisation about an exocyclic double bond. • The isomerism was investigated by 1H-, 13C-, 15N- and 19F-NMR spectroscopy in different solvents. • Gibbs free energies (ΔG) and Free activation energies (ΔG≠) were calculated based on DFT computations. [ABSTRACT FROM AUTHOR]