Oxalic Acid → 2-(2-Methoxy-5-phenylsulphonylphenyl)-5-[1-(1-piperidinyl)ethyl]-1H-pyrrole oxalate

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To 1-acetylpiperidine (0.61 ml) under argon, was added phosphorus oxychloride (0.45 ml) at ambient temperature. After stirring for 0.5 h 1,2-dichloroethane (10 ml) was added and the mixture cooled to 0° C. A solution of 2-(2-methoxy-3-phenylsulphonylphenyl)-1H-pyrrole (D25) (1.0 g) in 1,2-dichloroethane (10 ml) was added dropwise over 0.3 h. Stirring was continued at 0° C. for 3 h and at ambient temperature for 18 h. The mixture was cooled to 0° C. and sodium borohydride (1 g) added portionwise over 0.16 h. Stirring was continued at ambient temperature for 2.5 h before the mixture was cooled to 0° C. Water (5 ml) followed by MeOH (5 ml) was added dropwise followed by dilution with more water (50 ml). The mixture was extracted with dichloromethane (3×200 ml) and the combined extracts dried (Na2SO4) and evaporated in vacuo. Methanol (10 ml) and concentrated HCl (4.8 ml) were added and the mixture stirred for 4 h. Water (100ml) was added and the solution basified with NaOH (10%) and extracted with dichloromethane (3×200 ml). Combined extracts were dried (Na2SO4) and evaporated in vacuo. This material was dissolved in EtOAc and added to a hot solution of oxalic acid (1 equivalent) in EtOAc. Sufficient MeOH was added to dissolve the precipitated solid and the resultant solution cooled to give the title compound (E38) (0.27 g).

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