title: Structural elucidation of nitro-substituted five-membered aromatic heterocycles utilizing GIAO DFT calculations.
abstract: The GIAO (Gauge Including Atomic Orbitals) DFT (Density Functional Theory) method is applied at the B3LYP/6-31+G(d,p)//B3LYP/6-31+G(d), B3LYP/6-311++G(d,p)//B3LYP/6-31+G(d), B3LYP/6-311+G (2d,p)//B3LYP/6-31+G(d) and B3LYP/6-311++G(d,p)//B3LYP/6-311++G(d,p) levels of theory for the calculation of proton and carbon chemicals shifts and coupling constants for 25 nitro-substituted five-membered heterocycles. Difference (1D NOE) spectra in combination with long-range gHMBC experiments were used as tools for the structural elucidation of nitro-substituted five-membered heterocycles. The assigned NMR data (chemical shifts and coupling constants) for all compounds were found to be in good agreement with theoretical calculations using the GIAO DFT method. The magnitudes of one-bond (1JCH) and long-range (nJCH, n>1) coupling constants were utilized for unambiguous differentiation between regioisomers of nitro-substituted five-membered heterocycles.
authors.affiliation: Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA. katritzky@chem.ufl.edu
authors.forename: Alan R
authors.initials: AR
authors.lastname: Katritzky
authors.forename: Novruz G
authors.initials: NG
authors.lastname: Akhmedov
authors.forename: Jacek
authors.initials: J
authors.lastname: Doskocz
authors.forename: C Dennis
authors.initials: CD
authors.lastname: Hall
authors.forename: Rena G
authors.initials: RG
authors.lastname: Akhmedova
authors.forename: Suman
authors.initials: S
authors.lastname: Majumder
mesh_terms: D000465:Algorithms; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011720:Pyrazoles / Q000737:chemistry; D011758:Pyrroles / Q000737:chemistry*; D011789:Quantum Theory; D013876:Thiophenes / Q000737:chemistry
chemical_list: D006573:Heterocyclic Compounds, 1-Ring; D006841:Hydrocarbons, Aromatic; D007093:Imidazoles; D011720:Pyrazoles; D011758:Pyrroles; D013876:Thiophenes; C051763:thiophene A