Chlorosulfonic acid → Demethylpiperazinyl Desethyl Sildenafil Sulfonyl Chloride

Participants

Reaction Conditions

Reaction Steps

5-(2-Hydroxyphenyl)-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one (0.239 g, 0.00084 mol) was added, in portions, to stirred chlorosulphonic acid (3 ml) cooled to 0° C. under a nitrogen atmosphere, and the resulting deep red solution stirred at room temperature for 18 hours. The reaction mixture was then added dropwise, with care, to stirred ice/water to give a brown solid. The latter mixture was extracted with dichloromethane (3×30 ml), the combined extracts dried (Na2SO4) and filtered, and the filtrate evaporated under vacuum to give a brown solid (0.24 g, 75%), used in the next step without further purification; Rf 0.3 (silica; dichloromethane, methanol; 95:5).

Provenance & Evidence