To a solution of 19.16 g (58.1 mmol) of N-(1-benzylpiperidin-4-yl)-benzene sulfonamide in 300 mL of dimethoxyethane at 0° C. was added 46.4 mL (116.1 mmol) of a n-butyllithium (2.5 M) slowly via addition funnel. The mixture was stirred using an overhead stirrer for 45 minutes at 0° C., then 9.61 g (63.9 mmol) of p-chlorobenzaldehyde was added in one portion. The mixture was allowed to warm to room temperature, diluted with 1 liter of ethylacetate and washed 2×500 mL of water followed by 500 mL of brine. The organic phase was separated, dried (MgSO4), and concentrated in vacuo. The residue was flash chromatographed over 300 g of silica gel (eluted with ethylacetate:heptane-2:1) to afford 17.3 g of product as an orange paste.
