Substituent effects on the15N NMR Parameters of Azoles

Pyrazoles as molecular probes to study the properties of co-crystals by solid state NMR spectroscopy

“…C NMR signals of imidazoles 2-5 of Table 1 is straightforwarded by comparison with compounds 6-9 and references [30][31][32]. All the signals are Compound average and narrow indicating rapid N 1 -H/N 3 -H tautomerism.…”

“…N NMR spectroscopy of azoles have also been used for assignment purposes [30][31][32]. Table 1 The assignment of the…”

Multinuclear NMR study of Au(I), Pd(II) and Ag(I) pyrazole complexes to investigate the coordination mode

“…6 In 15 N-NMR, solid ammonium chloride was used as reference and the chemical shift data were transformed to external nitromethane through the equation: δ (NO 2 CH 3 ) = δ(NH 4 Cl) -338.1 ppm. 7 When analyzing the NMR parameters reported in Table 1 for 1 H-NMR, In solution, the 13 C-NMR data for C-3 and C-5 of HPz-(1) cannot be compared with those of the corresponding complexes because a mean value of 148.5 ppm, corresponding to the two degenerate forms a and b in fast exchange equilibrium, is observed at 300 K. 8 The coordination Although to a lesser extent, a similar effect takes place on C-ortho. However, the 13 C-CPMAS NMR of the pyrazole 1 presents two distinct values for C-3 and C-5 (150.3 and 144.4 ppm) as well as for the carbon atoms which correspond to the two 4-butoxyphenyl groups, meaning that the tautomeric equilibrium between forms a and b is frozen-in agreement with its X-ray structure.…”

Microwave Synthesis of Arylmethyl Substituted Pyrazoles

“…When dealing with compounds previously described, appropriate literature data are given. Most particularly, 13 C and 15 N-NMR data have provided to be the most useful to differentiate between N-and C-substitution taking into account chemical shifts and coupling constants data described in the literature for related compounds [9,[11][12][13]. For example in 1,4-bis(trityl)-1H-pyrazole (5a) the chemical shifts of Ci and C(sp 3 ) are quite different depending if the trityl group is at position N-1, 143.1 ppm and 78.5 ppm, or at position C-4, 147.0 ppm and 57.9 ppm, similarly to what has been described for 4a and found by us in 4-trityl-1H-pyrazole (6a), 1-trityl-3-methyl-1H-pyrazole (8a) and 3-methyl-1,4-bis(benzhydryl)-1H-pyrazole (10b).…”