Arkivoc 2017, iii, 55-62
Lyalin, B.V. et al
by column chromatography using petroleum ether : ethyl acetate as the eluent. Azopyrazole 1a that was
isolated (yield 3%) was identified using the characteristics reported previously10. The aqueous solution that
remained after the extraction (see above) was concentrated in vacuo and NaOH was added with stirring (to
pH~10). After that, the mixture was treated as described above. The hitherto unreported 3-amino-4-chloro-1-
methyl-1H-pyrazole 2 was isolated (yield 5%) and identified by NMR and HRMS methods. Non-reacted
aminopyrazole 1 (85% remained) was identified by TLC and 1H NMR methods.
One-pot conversion of aminopyrazole 1 to azopyrazole 1a involving electrogenerated NaOCl (experiment
with chronopotentiometry). Aminopyrazole 1 (1.5 mmol) and 4 M aqueous NaCl solution (50 ml) were placed
in a cell equipped with an Pt anode (S = 7.5 cm2) and a Ti cathode (S = 10 cm2) and electrolysis was carried out
at a current of 750 mA with simultaneous automatic measurement of the anode potential using potentiostat.
After electrolysis (Q = 289.5 C), the reaction mixture was stirred 0.5 h, treated, and analyzed as described
above. The yield of azopyrazole 1a was 3% and that of aminopyrazole 2 was 5%. The non-reacted remainder of
aminopyrazole 1 was 85%.
Two-stage conversion of aminopyrazole 1 to azopyrazole 1a and 1,2-bis(4-chloro-1-methyl-1H-pyrazol-3-
yl)diazene (3) involving electrogenerated NaOCl. Stage 1. Electrosynthesis of NaOCl. 100 ml of 4 M aqueous
NaCl solution was placed in the cell and electrolysis was carried out as indicated above (Q = 579 C) to give a
solution containing 2.3 mmol of NaOCl (according to iodometric analysis). Stage 2. Reaction of aminopyrazole
1 with NaOCl (ratio 1:1 or ratio 1:2). Aminopyrazole 1 (2.4 mmol or 1.2 mmol) was added to the NaOCl
solution obtained previously. The reaction mixture was stirred for 0.5 h, treated, and analyzed as described
above. The yield of azopyrazole 1a was 27% (or 40%), that of aminopyrazole 2 was 27% (or 7.4%), and that of
azopyrazole 3 was 7% (or 40%). The non-reacted remainder of aminopyrazole 1 was 26% (or 0%).
Two-stage conversion of 3-amino-1,4-dimethyl-1H-pyrazole (5) to 1,2-bis(1,4-dimethyl-1H-pyrazol-3-
yl)diazene (6) involving electrogenerated NaOCl. The procedure was carried out as described above using
aminopyrazole 5 (2.3 mmol). The yield of azopyrazole 6 was 66%. The non-reacted remainder of
aminopyrazole 5 was 34%.
1,2-Bis(1-methyl-1H-pyrazol-3-yl)diazene (1a). Yellow solid. mp 201 °C. 1H NMR (CDCl3, δ) 4.01 (s, 6H), 6.68 (d,
J 2.2 Hz, 2H), 7.36 (d, J 2.2 Hz, 2H) ppm. HRMS (ESI) calcd for C8H10N6 [M+H]+: 191.1040. Found 191.1043.
3-Amino-4-chloro-1-methyl-1H-pyrazole (2). White solid. mp 82 °C. 1H NMR (CDCl3, δ) 3.55 (br. s, 2H), 3.69 (s,
3H), 7.15 (s, 1H) ppm. 13С NMR (CDCl3, δ) 39.0 (CH3), 95.8 (C), 128.3 (CH), 150.5 (C) ppm. HRMS (ESI) calcd for
C4H6ClN3 [M+H]+: 132.0323. Found 132.0321.
1
1,2-Bis(4-chloro-1-methyl-1H-pyrazol-3-yl) diazene (3). Yellow solid. mp 215 °C. H NMR (CDCl3, δ) 4.00 (s,
6H), 7.48 (s, 2H) ppm. 13С NMR (CDCl3, δ) 41.0 (2CH3), 106.5 (C), 130.4 (2CH), 156.3 (2C) ppm. HRMS (ESI) calcd
for C8H8Cl2N6 [M]: 259.0260. Found 259.0254.
1,2-Bis(1,4-dimethyl-1H-pyrazol-3-yl)diazene (6). Yellow solid. mp 190 °C. 1H NMR (CDCl3, δ) 2.34 (s, 6H), 3.96
(s, 6H), 7.19 (s, 2H) ppm. 13С NMR (CDCl3, δ) 10.4 (2CH3), 39.5 (2CH3), 110.5 (2C), 131.2 (2CH), 150.6 (2C) ppm.
HRMS (ESI) calcd for C10H14N6 [M+H]+ 219.1353. Found 219.1352.
Acknowledgements
This study was supported by the Russian Foundation for Basic Research (Grant No. 16-03-00173 a).
Supplementary Material
Additional supporting information may be found in the online version of this article on the publisher’s web-
site.
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