title: Reinvestigation of the regiospecific outcome of heterocyclization of 3-hydrazino-1,2,4-triazino[5,6-b]indoles: angular versus linear annelated 1,2,4-triazolo-1,2,4-triazino[5,6-b]indole structures.
abstract: Divergences of the structural assignments reported in the literature for the products of cyclization of 3-hydrazino-1,2,4-triazino[5,6-b]indoles 1 with one-carbon cyclizing reagents have been reinvestigated. The linear annelated 1,2,4-triazolo[4,3-b]1,2,4-triazino[5,6-b]indoles 3 were found to be the products regiospecifically formed, rather than the angular annelated 1,2,4-triazolo[3,4-c]1,2,4-triazino[5,6-b]indoles 2. Our findings were based on comparison of the UV spectral data of the cyclization products with those of unequivocally as well as inevitably linear annelated compounds. Calculations of optimized geometries and electronic structures accord with the results obtained. Divergences reported in the literature were, therefore, attributed to erroneous structural assignments rather than to cyclization by different regiochemical pathways.
authors.affiliation: Department of Chemistry, Faculty of Science, Alexandria University, Alexandria, Egypt.
authors.forename: M A E
authors.initials: MA
authors.lastname: Shaban
authors.forename: A Z
authors.initials: AZ
authors.lastname: Nasr
authors.forename: A E A
authors.initials: AE
authors.lastname: Morgaan
mesh_terms: D000890:Anti-Infective Agents / Q000138:chemical synthesis; D000998:Antiviral Agents / Q000138:chemical synthesis; D002855:Chromatography, Thin Layer; D003500:Cyclization; D006571:Heterocyclic Compounds / Q000138:chemical synthesis*; D006834:Hydrazines / Q000737:chemistry; D007202:Indicators and Reagents; D007211:Indoles / Q000138:chemical synthesis; D009682:Magnetic Resonance Spectroscopy; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D014227:Triazines / Q000138:chemical synthesis
chemical_list: D000890:Anti-Infective Agents; D000998:Antiviral Agents; D006571:Heterocyclic Compounds; D006834:Hydrazines; D007202:Indicators and Reagents; D007211:Indoles; D014227:Triazines