5-Chlorothiophene-2-Sulfonamide → 5-Chloro-thiophene-2-sulfonic acid amino-(4,4-dimethyl-4,5-dihydro-pyrazol-1-yl)-methyleneamide

Participants

Reaction Steps

1.0 g (1 mol equiv.) 4,4-Dimethyl-4,5-dihydro-pyrazole-1-carboximidothioic acid methyl ester and 1.21 g (1.05 mol equiv.) 5-chloro-thiophene-2-sulfonic acid amide were added to 10 mL acetonitrile. The reaction mixture was refluxed overnight, and volatiles were removed under reduced pressure. The residue was taken up in ethyl acetate and extracted with 2N NaOH. The organic layer was dried over Na2SO4, filtered and evaporated to dryness. Purification by flash chromatography on silica gel (Et2O:PA=2:1) afforded 1.58 g (80%) 5-chloro-thiophene-2-sulfonic acid amino-(4,4-dimethyl-4,5-dihydro-pyrazol-1-yl)-methyleneamide. 1H NMR (400 MHz, CDCl3) δ 1.25 (s, 6H), 3.63 (s, 2H), 6.00-6.50 (br.s., 1H), 6.79 (s, 1H), 6.85 (d, J=4.0 Hz, 1H), 7.10-7.35 (br.s., 1H), 7.37 (d, J=4.0 Hz, 1H).

Provenance & Evidence