NMR studies in the heterocyclic series XXIV—¹H, ¹³C and ¹⁵N study of ¹⁵N labelled indazoles

Bond Length Alternation Observed Experimentally: The Case of 1H‐Indazole

“…This is a modification of one of the methods to synthesise 1 H ‐indazole by replacing sodium nitrite with sodium nitrite‐ 15 N (98 atom % of 15 N, Sigma–Aldrich 490814). For NMR studies, we have already used this procedure to prepare [ 15 N 2 ]‐1 H ‐indazole . From labelled sodium nitrite (3.6 g), we obtained labelled indazole (3.18 g, overall yield=52 %).…”

The 15N induced isotope shift as an effective tool for the structure elucidation of 2,4 and 2,5 di-substituted thiazoles

“…In fact literature data report study cases with 2 J C-N > 1 J C-N, for methyl substituent in pyridin like systems. 7 Instead a 3 J C-N > 1 J C-N , as it would be for the 2,5 regioisomer, looks quite unrealistic and is not supported by any reference. All these evidences significantly suggested the investigated compound to be the 2,4 regioisomer, but did not provide alone an unambiguous structure elucidation.…”

“…In particular, the successful use of 15 N labeling in the structural investigation of indazoles is well documented. 7 Being 15 N labeled sodium thiocyanate a cheap and commercially available reagent, we applied our procedure (Scheme 1) to obtain 15 N labeled isotopologue DFL23836 (1-15 N). 8 Product 1-15 N (Fig.…”

Five‐Membered Heterocycles: 1,2‐Azoles. Part 1. Pyrazoles

“…Note that the 15 N chemical shifts are very sensitive to hydrogen bonds and, obviously, to protonation. ) 3524 (n NH gas) [4] Source: [11] X-ray (CSD) [12] PYRZOL INDAZL 1 H NMR Source: [13] Source: [13,14] 13 C NMR Source: [15] Source: [16] 15 N NMR Source: [17] Source: [ Source: [22] Source: [23] Best theoretical calculations Source: [24] Source: [25] Aromaticity (benzene ¼ 0.991) 0.900: [26] 0.808: [26] a) a) Naphthalene: 0.811, 2H-indazole: 0.792 (using as criteria the HOMA) [27]. 111.9 NMR information on the non-aromatic derivatives of pyrazoles is very abundant, particularly on D 2 -pyrazolines and on pyrazolones [4,7].…”

“…Analgesics were, by far, the main area of biological activity of pyrazoles, often associated with antipyretic activity. They belong to three main classes: pyrazolin-5-ones [antipyrine -phenazone -(12), pyramidon (13), dipyrone (14)], pyrazolin-3,5-diones [phenylbutazone (15)] and pyrazoles [actually, an acetic acid, lonazolac (16)] [46].…”