Piperazine → 2-[2-Ethoxy-5-(1-piperazinylsulphonyl)pheny]-8-methylquinazolin-4(3H)-one

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Reaction Steps

2-(2-Ethoxyphenyl)-8-methylquinazolin-4(3H)-one (Preparation 4; 2.1 g, 0.0071 mol) was added portionwise to stirred chlorosulfonic acid (15 ml) under a nitrogen atmosphere at 0° C. After 18 hours, the mixture was cautiously added dropwise to stirred ice/water (100 g) and the resulting mixture extracted with dichloromethane-methanol (9:1, 10×100 ml). The organic extracts were combined, dried (MgS4) and evaporated under vacuum. A quantity (1.0 g) of the crude sulphonyl chloride was then added portionwise to a stirred solution of piperazine (2.1 g, 0.0244 mol) in ethanol (30 ml) at room temperature under a nitrogen atmosphere. After 18 hours the mixture was poured into stirred saturated aqueous sodium carbonate solution (100 ml) and the resulting mixture extracted with dichloromethane-methanol (9:1, 10×100 ml). The organic extracts were combined, dried (MgS4) and evaporated under vacuum to give the title compound, which crystallized from ethanol as a colorless solid (0.8 g, 71%), m.p. 163°-165 ° C. Found: C,56.76; H,5.72; N,11.77. C21H4N4O5S; 0.75 C2H5OH requires C,56.41; H,6.00; N,11.70%.

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