A facile access to new diazepines derivatives: Spectral characterization and crystal structures of 7-(thiophene-2-yl)-5-(trifluoromethyl)-2,3-dihydro-1H-1,4-diazepine and 2-thiophene-4-trifluoromethyl-1,5-benzodiazepine

• Published in: Journal of molecular structure 2016-12, Vol.1125, p.781-787
• Main Authors: Ahumada, Guillermo, Carrillo, David, Manzur, Carolina, Fuentealba, Mauricio, Roisnel, Thierry, Hamon, Jean-René
• Format: Article
• Language: English
• Subjects: 2-Thenoyltrifluoroacetone; Benzodiazepine; Chemical Sciences; Diazepine; Imine-enamine tautomerism; Single-crystal X-ray diffraction; Trifluoroacethyl-derivatives
• ISSN: 0022-2860; 1872-8014; 0022-2860
• DOI: 10.1016/j.molstruc.2016.07.047

The one-pot double condensation reaction of 2-thenoyltrifluoroacetone (2-TTA) with ethylendiamine or o-phenylenediamine, in a 2:1 stoichiometric molar ratio, leads to the formation of 7-(thiophene-2-yl)-5-(trifluoromethyl)-2,3-dihydro-1H-1,4-diazepine 2 and 2-thiophene-4-trifluoromethyl-1,5-benzodiazepine 3, that were isolated in 56 and 53% yields, respectively. The bis(trifluoroacetamide)ethylene derivative 1 was also isolated in 32% yield as a side-product in the reaction of 2-TTA and ethylenediamine. Compounds 1–3 were fully characterized by elemental analysis, FT-IR and multinuclear (1H, 13C and 19F) NMR spectroscopy. In addition, their molecular identities and geometries have been authenticated by single-crystal X-ray diffraction analysis. The spectroscopic and structural data confirm that the 1,4-diazepine 2 and the 1,5-benzodiazepine 3 exist in the imine-enamine and diimine tautomeric forms, respectively, both in solution and in the solid-state. Both thienyl-containing 1,4-diazepine and 1,5-benzodiazepine (illustrated) were synthetized in a one-pot double condensation reaction of 2-thenoyltrifluoroacetone with ehtylenediamine and o-phenylene diamine, respectively. [Display omitted] •Synthesis of 1,4-diazepine by double condensation of TTA with ethylenediamine.•Synthesis of 1,5-benzodiazepine by double condensation of TTA with o-diaminophenyl•X-ray crystal structures of both diazepines.•1,4-Diazepine exists as imine-enamine tautomer in solution and in the solid-state.•1,5-Benzodiazepine exists as diimine tautomer in solution and in the solid-state.