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.

Nitration of pyridines 1a-o with nitric acid in trifluoroacetic anhydride, gave the corresponding 3-nitropyridines 6a-n in yields of 10-83%.

Direct nitration of a variety of furans, pyrroles, thiophenes, pyrazoles, imidazoles, isoxazoles and thiazoles (17 compounds) with nitric acid/trifluoroacetic anhydride affords mononitro derivatives in average yield of 60 %.

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Reactions of alkylazines 9a−f (2-methylpyridine, 2-benzylpyridine, 4-benzylpyridine, 2-methylquinoline, 4-methylquinoline or 4-methylpyrimidine) with readily available N-acylbenzotriazoles 8a−j produced 1-substituted-2-azinyl-1-ethanones 10a−p in 50−95% yields.