Sulfuric Acid → 2-(4-Chloro-2-fluoro-5-hydroxyphenyl)hexahydro-3-thioxo-1H-[1,2,4]triazolo[1,2-a]pyridazin-1-one

Participants

Reaction Conditions

Reaction Steps

Conc. sulfuric acid (22 ml) was added dropwise to a solution of 2-[4-chloro-2-fluoro-5-(isopropyloxy)phenyl]hexahydro-3-thioxo-1H-[1,2,4]triazolo[1,2-a]pyridazin-1-one (17.2 g) in methylene chloride (120 ml) stirred at 0° C. The mixture was stirred at room temperature for 1 hour and ice-water (200 g) added. The aqueous phase was extracted with methylene chloride and the organic phases combined, dried over sodium sulfate and chromatographed (silica gel, ethyl acetate) to give the product (14.5 g, 96%). 1H NMR (CDCl3, TMS): 1.84(4H, m), 3.82(4H, m), 7.06(1H, d, J=6.5 Hz), 7.58(1H, d, J=8.8 Hz), 10.6(1H, s).

Provenance & Evidence