On triazoles. IV—NMR study of 5‐amino‐1,2,4‐triazole isomers

Abstract

A 'H NMR and % ! NMR study of all possible isomers of monoalkylated 3-methylthio-5-amino-1,2,4-triazoles was carried out. The %NMR spectra, including the corresponding proton coupled measurements, proved unambiguously the structures of all derivatives studied.In the preceding papers of this series'32 we reported the syntheses of different A-D type 1,2,4-triazole derivatives. It was shown that neither the MS method proposed for the differentiation between A and B3 nor the study of the IR and UV spectra of derivatives A-D was suitable for a complete structural determination of these isomers. We also showed that previous 'H NMR investigation^^,^ of derivatives 2A and 2B led to erroneous results. ' In order to establish a general rule for the differentiation between derivatives A-D, systematic NMR investigations were initiated. EXPERIMENTALThe 'HNMR spectra were recorded on Varian EM-390, Bruker WM-250, or WP-80SY instruments at 90, 250 or 80 MHz, respectively, in the CW or FT mode, at ambient temperature. The 13CNMR spectra were recorded on Varian XL-100, Bruker WM-250, or WP-80SY F T spectrometers. Typical measuring conditions were as follows: temperature, ca 40 OC; pulse width, 15, 5 and 3.5 p s , respectively (30-45"); spectral width, 5, 16 and 5 kHz, respectively; data points, 16, 32 and 16K, respectively; acquisition time, 0.8, 1.02 and 1.64 s, respectively; relaxation delay, 0-1.0 s, using broad band proton decoupling. The proton coupled spectra were recorded using the gated decoupling technique, with the same parameters except that of the repetition time (3.0 s). The transform sizes were 8, 16 and 8K, respectively. To attain better digital resolution, some proton coupled spectra were also taken with a sweep width of 500 or 1000 Hz.The solvent (except when stated otherwise) was DMSO-d6, with DSS as internal reference. Chemical shifts are quoted relative to TMS in CDCl, solution, and relative to DSS in DMSO solutions, for concentrations of approximately 10%. RESULTS 'H NMR spectroscopyThe 'HNMR spectra (Table 1)

On triazoles XLVIII. Synthesis of isomeric amino‐thiazolo‐[1,2,4]triazole, amino‐[1,2,4]triazolo‐[1,3]thiazine and ‐[1,3]thiazepine derivatives

“…This is in full analogy with those of the corresponding carbon atoms of the 2-and 4-alkylated 5-amino-3-alkylthio-1,2,4-triazoles (Scheme 6) reported previously [20].…”

“…The chemical shift of the amino groups of derivatives 1 and 2 taken in DMSO-d 6 solution significantly differed appearing between 5.18 and 5.37, and 5.72 and 5.92 ppm, respectively, in good agreement with those of 2-and 4-alkylated 5-amino-3-alkylthio-1,2,4-triazoles (Scheme 6) reported previously [20] giving an evidence of their structure.…”

Alkylation of acyl and sulfonyl derivatives of 3,5-diamino-1-phenyl-1,2,4-triazole

“…The values of the chemical shifts of the triazole ring carbon atoms in the 13 C NMR spectra of compounds 2b,c,f-h (C-3 155-158 and C-5 154 ppm) are close to those of other 1-R-3,5-diamino-1,2,4-triazoles [8,15]. In the proton-coupled 13 C NMR spectra the signal for the C-3 atom is split due to spin-spin coupling interaction through three bonds with the alkyl group protons to a triplet in compounds 2b,c,f,h (J = 3.5-4.1) and to a quartet in the methyl derivative 2g (J = 2.9 Hz) while the signal for the C-5 atom is a singlet (spin-spin interaction of the carbon nucleus with amino group protons not being observed due to rapid exchange of these protons with the solvent [15,16]). Hence one can exclude a 4-alkyl-substituted alternative structure since a splitting of the C-5 signal due to 437 interaction with alkyl group protons would be observed [8,16].…”

On triazoles XLIII. Synthesis of 1,2,4‐triazolyl isoquinolinium zwitter ions

“…Recently, we have reported on the synthesis of pyrazolyl (5) and tetrazolyl (6) isoquinolinium zwitter ions by the reaction of the 1 type ortho-acylphenylacetones or the 2 type pyrylium salts formed from 1 with perchloric acid and different 3-amino-pyrazoles (3) and 5-amino-tetrazoles (4), respectively [2] (Scheme 1).…”