Synthesis and Solution Structure of 1H‐Benzo‐1,5‐diazepine Derivatives with a Perfluoroalkyl Side Chain

Abstract

The reaction of perfluorinated 3,5‐dioxoesters with 1,2‐diaminobenzenes or 2,3‐diaminonaphthalenes afforded two types of 1H‐benzo‐1,5‐diazepine derivatives containing a perfluorinated side chain. 2,5‐Dihydro‐1H‐benzo‐1,5‐diazepin‐2‐ones were formed by cyclocondensation via the central keto and the ester group, whereas 1H‐benzo‐1,5‐diazepines resulted from cyclocondensation via the two keto groups. The tautomerism and isomerization of these compounds have been investigated by 1H‐, 13C‐, and 19F‐NMR spectroscopy. The 1,5‐diazepines appear in CDCl3 solution as mixtures of two tautomeric forms, the enaminoimine I and diaminodiene II. In DMSO solution, besides I and II, two further species, III and IV, are formed by (E/Z) isomerization on the exocyclic C=C bond.

NMR Spectroscopic and Theoretical Studies on Tautomerism and Isomerism of Perfluoroalkyl‐Substituted 1,5‐Benzodiazepines

“…The spectral assignment to I–IV was performed on the basis of signal intensities, chemical shifts and 1 H, 1 H‐ and 13 C, 19 F‐coupling constants as well as the results of two‐dimensional NMR measurements ( 1 H, 1 H‐COSY, 1 H, 1 H‐NOESY (EXSY), 1 H, 13 C‐ and 1 H, 15 N‐chemical shift correlation spectra (HSQC and HMBC)). For example, the correlations found in the 1 H, 13 C‐HMBC spectrum of 3 f correspond with the proposed structures (Figure and Figure S1) …”

“…In contrast to compounds 1 and 2 , in the NMR spectra of 3 a and 3 f in (D 6 )DMSO solution, signals of four isomers were observed. This different behaviour of compounds 3 to 1 and 2 motivated us – in extension to our preliminary communication – to investigate the isomerism of 3 more thoroughly including further solvents and representatives of 3 as well as 15 N and 19 F NMR measurements. In addition, quantum chemical computations should be carried out to support the experimental findings.…”

“…1,5‐Benzodiazepines exist in general in one tautomeric form, preferred in the bis‐imino tautomer . In case of 1,5‐benzodiazepines that possess exocyclic methylenecarbonyl groups, further tautomers have to be considered . For example, Yachevskii et al .…”

“…We have recently described the benzodiazepine‐2‐ones 2 and benzodiazepines 3 , which possess, in contrast to 1 , only a single perfluorinated side chain (Figure ).…”

Reactions of Trifluorotriacetic Acid Lactone and Hexafluorodehydroacetic Acid with Amines: Synthesis of Trifluoromethylated 4-Pyridones and Aminoenones

“…Benzodiazepinone 10 was formed as the only isolated product, although the yield was moderate ( Scheme 9 ). Compound 10 was previously obtained from the corresponding dioxoester 11 in the mixture with diazepine 12 [ 43 ] ( Scheme 9 ), so our method represents a good alternative with no specific separation needed.…”