A mixture of ethyl 3-(1-(3-(thioxanthen-9-ylidene)-1-propyl)piperidin-4-yl)propionate (as the free base released from the above hydrogen oxalate; 3.71 g, 0.0088 mol), 4 N sodium hydroxide (10 ml) and 96% ethanol (70 ml) was stirred at room temperature overnight. Ethanol was evaporated in vacuo, the residue was dissolved in water (50 ml) and the aqueous solution was washed with diethyl ether (50 ml). The aqueous phase was neutralised with acetic acid and extracted with dichloromethane (3×150 ml). The combined dichloromethane extracts tracts were dried (MgSO4) and evaporated in vacuo. The residue was dissolved in acetone (30 ml), the solution was diluted with diethyl ether (30 ml) and the mixture was stirred for 1 h. The precipitated solid was filtered off, washed with acetone and dried in vacuo, affording 2.24 g (56%) of the title compound.
