Bis[(3-methoxycarbonyl-5-methyl pyrazol)-1-yl Thiocarbonyl] Disulfide

This experiment is performed according to literature method [1,2,3,4]. 3(5)-Methoxycarbonyl-5(3)-pyrazole 1 (3.35 g, 0.024 mol) and triethylamine (6,65 g, 0.048 mol) in ethanol solution were cooled to 5°C under stirring, carbon disulfide (3,65 g, 0.048 mol) was added to the solution. After 1 hour of stirring, solid iodine (2,8 g, 0.022 mol) was added in portions and stirred until the colour disappeared completely. Then a methanolic solution of iodine was added dropwise until a faint colour persists. Excess of iodine was neutralized with Na₂S₂O₃ solution. The product was extracted with diethyl ether, washed thrice with water, dried over Na₂SO₄, filtered, and diethylether was evaporated at room temperature to give liquid compound 2.

Yield: (90%).

¹H-NMR(CDCl₃) d (ppm): 2,30 (s, 6H, CH₃); 4,86 (s, 6H, CO₂CH₃); 6,53 (s, 2H, Hpy).

¹³C-NMR(CDCl₃) d (ppm): 166 (CO₂), 126 (C₃), 52 (O-CH₃)

IR (KBr , cm^-1) : 3200 (-S-S-); 1720 (C=O); 1240 (C=S), 166 (CO₂), 126 (C₃), 52 (O-CH₃).

MS (m/z): 430 [M]⁺.

U.V.: l_max = 290 nm (-C=S).