Methanol → 4-Quinazolineacetic acid, 8-fluoro-3,4-dihydro-2-[4-(3-methoxyphenyl)-1-piperazinyl]-3-[2-methoxy-5-(trifluoromethyl)phenyl]-, methyl ester

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(±)-{8-Fluoro-2-[4-(3-methoxyphenyl)piperazin-1-yl]-3-(2-methoxy-5-trifluoromethylphenyl)-3,4-dihydroquinazolin-4-yl}acetic acid (148 g) is dissolved in methanol (1480 g), then concentrated sulphuric acid (21.5 ml) is added. The mixture is stirred under reflux for 6 h, then cooled and concentrated to ca. one third of the original volume in vacuo. Water (400 ml) and dichloromethane (400 ml) are added, then the phases are separated. The organic phase is extracted with saturated sodium hydrogencarbonate solution (two times 375 ml, diluted with 300 ml of water), dried over sodium sulphate and concentrated to give a foamy residue. This is dissolved twice in succession in ethanol (400 ml each) and concentrated, and subsequently dried in vacuo for 18 h using entraining nitrogen. A total of 124 g of methyl {8-fluoro-2-[4-(3-methoxyphenyl)piperazin-1-yl]-3-[2-methoxy-5-(trifluoromethyl)phenyl]-3,4-dihydroquinazolin-4-yl}acetate are thus obtained as an amorphous solid, corresponding to 81.9% of theory.

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