A stirred suspension of N-[(1-n butyl-4-piperidyl)methyl] indole-3-carboxamide (Description 1b, 1.0 g, 0.0032 mole) in chloroform (25 ml) was treated with 4-chlorobutanol (0.69 ml, 0.0064 mole) followed by N-chlorosuccinimide (470 mg, 0.0035 mole) and a yellow solution was produced inside 5 minutes. After a further 40 minutes the solution was observed to darken in colour to orange. The mixture was kept at room temperature for a further 1 h then treated with 10% Na2CO3 solution (30 ml) and extracted with chloroform (2×30 ml). The combined extracts were dried (Na2SO4) and concentrated in vazcuo to afford an orange oil, which was chromatographed on silica gel eluting with 5% methanol/chloroform to give N-[(1-n butyl-4-piperidyl)methyl]2-(4-chlorobutoxy)indole-3-carboxamide (0.67 g, 50%) as a yellow oil.
